Papers on health effects of increased CO2

This is a list of papers dealing with different aspects of the health effects of increased carbon dioxide. The list contains subsections for general studies, increasing atmospheric CO2 and allergies, and extreme carbon dioxide events. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (August 27, 2019): Zhang et al. (2017), Zhang et al. (2017), Allen et al. (2016), Hersoug et al. (2012) and Satish et al. (2012) added.
UPDATE (April 11, 2013): New section for atmospheric carbon dioxide and allergies added including 10 papers.
UPDATE (November 9, 2011): Robertson (2006) added.

General studies

Physiological responses during exposure to carbon dioxide and bioeffluents at levels typically occurring indoors – Zhang et al. (2017) [Full text]
Abstract: Twenty‐five subjects were exposed to different levels of carbon dioxide (CO2) and bioeffluents. The ventilation rate was set high enough to create a reference condition of 500 ppm CO2 with subjects present; additional CO2 was then added to supply air to reach levels of 1000 or 3000 ppm, or the ventilation rate was reduced to allow metabolically generated CO2 to reach the same two levels (bioeffluents increased as well). Heart rate, blood pressure, end‐tidal CO2 (ETCO2), oxygen saturation of blood (SPO2), respiration rate, nasal peak flow, and forced expiration were monitored, and the levels of salivary α‐amylase and cortisol were analyzed. The subjects performed a number of mental tasks during exposures and assessed their levels of comfort and the intensity of their acute health symptoms. During exposure to CO2 at 3000 ppm, when CO2 was added or ventilation was restricted, ETCO2 increased more and heart rate decreased less than the changes that occurred in the reference condition. Exposure to bioeffluents, when metabolically generated CO2 was at 3000 ppm, significantly increased diastolic blood pressure and salivary α‐amylase level compared with pre‐exposure levels, and reduced the performance of a cue‐utilization test: These effects may suggest higher arousal/stress. A model is proposed describing how mental performance is affected by exposure to bioeffluents.
Citation: Zhang, X. , Wargocki, P. and Lian, Z. (2017), Physiological responses during exposure to carbon dioxide and bioeffluents at levels typically occurring indoors. Indoor Air, 27: 65-77. doi:10.1111/ina.12286.

Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self‐assessed acute health symptoms, and cognitive performance – Zhang et al. (2017) [Full text]
Abstract: The purpose of this study was to examine the effects on humans of exposure to carbon dioxide (CO2) and bioeffluents. In three of the five exposures, the outdoor air supply rate was high enough to remove bioeffluents, resulting in a CO2 level of 500 ppm. Chemically pure CO2 was added to this reference condition to create exposure conditions with CO2 at 1000 or 3000 ppm. In two further conditions, the outdoor air supply rate was restricted so that the bioeffluent CO2 reached 1000 or 3000 ppm. The same 25 subjects were exposed for 255 min to each condition. Subjective ratings, physiological responses, and cognitive performance were measured. No statistically significant effects on perceived air quality, acute health symptoms, or cognitive performance were seen during exposures when CO2 was added. Exposures to bioeffluents with CO2 at 3000 ppm reduced perceived air quality; increased the intensity of reported headache, fatigue, sleepiness, and difficulty in thinking clearly; and reduced speed of addition, the response time in a redirection task, and the number of correct links made in the cue‐utilization test. This suggests that moderate concentrations of bioeffluents, but not pure CO2, will result in deleterious effects on occupants during typical indoor exposures.
Citation: Zhang, X. , Wargocki, P. , Lian, Z. and Thyregod, C. (2017), Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self‐assessed acute health symptoms, and cognitive performance. Indoor Air, 27: 47-64. doi:10.1111/ina.12284.

Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments – Allen et al. (2016) [Full text]
Abstract: Background: The indoor built environment plays a critical role in our overall well-being because of both the amount of time we spend indoors (~90%) and the ability of buildings to positively or negatively influence our health. The advent of sustainable design or green building strategies reinvigorated questions regarding the specific factors in buildings that lead to optimized conditions for health and productivity. Objective: We simulated indoor environmental quality (IEQ) conditions in “Green” and “Conventional” buildings and evaluated the impacts on an objective measure of human performance: higher-order cognitive function. Methods: Twenty-four participants spent 6 full work days (0900–1700 hours) in an environmentally controlled office space, blinded to test conditions. On different days, they were exposed to IEQ conditions representative of Conventional [high concentrations of volatile organic compounds (VOCs)] and Green (low concentrations of VOCs) office buildings in the United States. Additional conditions simulated a Green building with a high outdoor air ventilation rate (labeled Green+) and artificially elevated carbon dioxide (CO2) levels independent of ventilation. Results: On average, cognitive scores were 61% higher on the Green building day and 101% higher on the two Green+ building days than on the Conventional building day (p < 0.0001). VOCs and CO2 were independently associated with cognitive scores. Conclusions: Cognitive function scores were significantly better under Green+ building conditions than in the Conventional building conditions for all nine functional domains. These findings have wide-ranging implications because this study was designed to reflect conditions that are commonly encountered every day in many indoor environments.
Citation: Allen JG, MacNaughton P, Satish U, Santanam S, Vallarino J, Spengler JD. 2016. Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers: a controlled exposure study of green and conventional office environments. Environ Health Perspect 124:805–812; http://dx.doi.org/10.1289/ehp.1510037.

A proposed potential role for increasing atmospheric CO2 as a promoter of weight gain and obesity – Hersoug et al. (2012) [Full text]
Abstract: Human obesity has evolved into a global epidemic. Interestingly, a similar trend has been observed in many animal species, although diet composition, food availability and physical activity have essentially remained unchanged. This suggests a common factor—potentially an environmental factor affecting all species. Coinciding with the increase in obesity, atmospheric CO2 concentration has increased more than 40%. Furthermore, in modern societies, we spend more time indoors, where CO2 often reaches even higher concentrations. Increased CO2 concentration in inhaled air decreases the pH of blood, which in turn spills over to cerebrospinal fluids. Nerve cells in the hypothalamus that regulate appetite and wakefulness have been shown to be extremely sensitive to pH, doubling their activity if pH decreases by 0.1 units. We hypothesize that an increased acidic load from atmospheric CO2 may potentially lead to increased appetite and energy intake, and decreased energy expenditure, and thereby contribute to the current obesity epidemic.
Citation: L-G Hersoug, A Sjödin & A Astrup (2012). Nutrition & Diabetes volume 2, page e31. doi:10.1038/nutd.2012.2.

Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance – Satish et al. (2012) [Full text]
Abstract: Background: Associations of higher indoor carbon dioxide (CO2) concentrations with impaired work performance, increased health symptoms, and poorer perceived air quality have been attributed to correlation of indoor CO2 with concentrations of other indoor air pollutants that are also influenced by rates of outdoor-air ventilation. Objectives: We assessed direct effects of increased CO2, within the range of indoor concentrations, on decision making. Methods: Twenty-two participants were exposed to CO2 at 600, 1,000, and 2,500 ppm in an office-like chamber, in six groups. Each group was exposed to these conditions in three 2.5-hr sessions, all on 1 day, with exposure order balanced across groups. At 600 ppm, CO2 came from outdoor air and participants’ respiration. Higher concentrations were achieved by injecting ultrapure CO2. Ventilation rate and temperature were constant. Under each condition, participants completed a computer-based test of decision-making performance as well as questionnaires on health symptoms and perceived air quality. Participants and the person administering the decision-making test were blinded to CO2 level. Data were analyzed with analysis of variance models. Results: Relative to 600 ppm, at 1,000 ppm CO2, moderate and statistically significant decrements occurred in six of nine scales of decision-making performance. At 2,500 ppm, large and statistically significant reductions occurred in seven scales of decision-making performance (raw score ratios, 0.06–0.56), but performance on the focused activity scale increased. Conclusions: Direct adverse effects of CO2 on human performance may be economically important and may limit energy-saving reductions in outdoor air ventilation per person in buildings. Confirmation of these findings is needed.
Citation: Usha Satish, Mark J. Mendell, Krishnamurthy Shekhar, Toshifumi Hotchi, Douglas Sullivan, Siegfried Streufert, William J. Fisk (2012). Environmental Health Perspectives, 120(12). doi:10.1289/ehp.1104789.

High carbon dioxide concentrations in the classroom: the need for research on the effects of children’s exposure to poor indoor air quality at school – Miller et al. (2010) “Air quality and its effect on health have received recent attention from the House of Commons Environmental Audit Committee. 1 While outdoor air pollution is clearly important and contributes to indoor air quality, indoor air pollution sources and the time spent in indoor environments are key to understanding exposure.” Janice Miller, Sean Semple, Stephen Turner, Occup Environ Med 2010;67:799 doi:10.1136/oem.2010.057471.

Occupational hazards of carbon dioxide exposure – Scott et al. (2009) “This paper is an overview of the occupational hazards that result from exposure to carbon dioxide. It details the main uses, characteristics, and problems that have been identified when carbon dioxide is utilized in various working environments. Carbon dioxide is always a danger when present in enclosed spaces at elevated concentrations. Situations resulting from acute and chronic exposures involving the gaseous and dry ice forms of carbon dioxide are discussed in detail. Current rationale concerning exposure limits and monitoring recommendations are highlighted.” Jonathan L. Scott, David G. Kraemer, Randal J. Keller, Journal of Chemical Health and Safety, Volume 16, Issue 2, March-April 2009, Pages 18-22, doi:10.1016/j.jchas.2008.06.003.

Effects of carbon dioxide inhalation on psychomotor and mental performance during exercise and recovery – Vercruyssen et al. (2007) “On separate days, 6 highly trained participants performed psychomotor tests while breathing for 60 min 3 carbon dioxide (CO(2)) mixtures (room air, 3% CO(2), or 4% CO(2)) prior to, between, and following two 15-min treadmill exercise bouts (70% VO(2)(max)). Each individual was extensively practiced (at least 4 days) before testing began, and both gas conditions and order of tasks were counterbalanced. Results showed physiological reactions and work-related psychomotor effects, but no effects of gas concentration on addition, multiplication, grammatical reasoning, or dynamic postural balance. These findings help define behavioral toxicity levels and support a re-evaluation of existing standards for the maximum allowable concentrations (also emergency and continuous exposure guidance levels) of CO(2). This research explored the selection of psychometric instruments of sufficient sensitivity and reliability to detect subtle changes in performance caused by exposure to low levels of environmental stress, in this case differential levels of CO(2) in the inspired air.” Vercruyssen M, Kamon E, Hancock PA., Int J Occup Saf Ergon. 2007;13(1):15-27. [Full text]

Health effects of increase in concentration of carbon dioxide in the atmosphere – Robertson (2006) “The toxic effects, to humans and other mammals, of concentrations of carbon dioxide in the atmosphere which are below the safe working level but above the present level are described. The likely physiological effects of the predicted increase in concentration of carbon dioxide in the atmosphere over the next 50 years are detailed.” A quote from the article: “At a carbon dioxide concentration of 600 ppm in an indoor atmosphere, the occupants become aware of deterioration in the atmosphere. At and above this level, some occupants began to display one or more of the classic symptoms of carbon dioxide poisoning, e.g. difficulty in breathing, rapid pulse rate, headache, hearing loss, hyperventilation, sweating and fatigue. At 1000 ppm, nearly all the occupants were affected. […] In the event that the atmospheric concentration of carbon dioxide reaches 600 ppm, the planet will have a permanent outdoor atmosphere exactly like that of a stuffy room. The conditions indoors in buildings of the type now available will become even more unpleasant and could easily reach 1000 ppm permanently with the results outlined above.” D. S. Robertson, Current science, 2006, vol. 90, no12, pp. 1607-1609. [Full text]

Carbon Dioxide Poisoning – Langford (2005) “Carbon dioxide is a physiologically important gas, produced by the body as a result of cellular metabolism. It is widely used in the food industry in the carbonation of beverages, in fire extinguishers as an `inerting’ agent and in the chemical industry. Its main mode of action is as an asphyxiant, although it also exerts toxic effects at cellular level. At low concentrations, gaseous carbon dioxide appears to have little toxicological effect. At higher concentrations it leads to an increased respiratory rate, tachycardia, cardiac arrhythmias and impaired consciousness. Concentrations >10% may cause convulsions, coma and death. Solid carbon dioxide may cause burns following direct contact. If it is warmed rapidly, large amounts of carbon dioxide are generated, which can be dangerous, particularly within confined areas. The management of carbon dioxide poisoning requires the immediate removal of the casualty from the toxic environment, the administration of oxygen and appropriate supportive care. In severe cases, assisted ventilation may be required. Dry ice burns are treated similarly to other cryogenic burns, requiring thawing of the tissue and suitable analgesia. Healing may be delayed and surgical intervention may be required in severe cases.” Langford, Nigel J., Toxicological Reviews, Volume 24, Number 4, 2005 , pp. 229-235(7).

Association of Ventilation Rates and CO₂ Concentrations with Health andOther Responses in Commercial and Institutional Buildings – Seppänen et al. (1999) “This paper reviews current literature on the associations of ventilation rates and carbon dioxide concentrations in non-residential and non-industrial buildings (primarily offices) with health and other human outcomes. Twenty studies, with close to 30,000 subjects, investigated the association of ventilation rates with human responses, and 21 studies, with over 30,000 subjects, investigated the association of carbon dioxide concentration with these responses. Almost all studies found that ventilation rates below 10 Ls^-1 per person in all building types were associated with statistically significant worsening in one or more health or perceived air quality outcomes. Some studies determined that increases in ventilation rates above 10 Ls^-1 per person, up to approximately 20 Ls^-1 per person, were associated with further significant decreases in the prevalence of sick building syndrome (SBS) symptoms or with further significant improvements in perceived air quality. The carbon dioxide studies support these findings. About half of the carbon dioxide studies suggest that the risk of sick building syndrome symptoms continued to decrease significantly with decreasing carbon dioxide concentrations below 800 ppm. The ventilation studies reported relative risks of 1.5–2 for respiratory illnesses and 1.1–6 for sick building syndrome symptoms for low compared to high low ventilation rates.” O. A. Seppänen, W. J. Fisk, M. J. Mendell, Indoor Air, Volume 9, Issue 4, pages 226–252, December 1999, DOI: 10.1111/j.1600-0668.1999.00003.x. [Full text]

Indoor Air Quality Investigations at Five Classrooms – Lee & Chang (1999) “Five classrooms, air-conditioned or naturally ventilated, at five different schools were chosen for comparison of indoor and outdoor air quality. Temperature, relative humidity (RH), carbon dioxide (CO₂), sulphur dioxide (SO₂), nitric oxide (NO), nitrogen dioxide (NO₂), particulate matter with diameter less than 10 mm (PM₁₀), formaldehyde (HCHO), and total bacteria counts were monitored at indoor and outdoor locations simultaneously. Respirable particulate matter was found to be the worst among parameters measured in this study. The indoor and outdoor average PM₁₀ concentrations exceeded the Hong Kong standards, and the maximum indoor PM₁₀ level was even at 472 μ;g/m³. Air cleaners could be used in classrooms to reduce the high PM₁₀ concentration. Indoor CO₂ concentrations often exceeded 1,000 μl/l indicating inadequate ventilation. Lowering the occupancy and increasing breaks between classes could alleviate the high CO₂ concentrations. Though the maximum indoor CO₂ level reached 5,900 μl/l during class at one of the sites, CO₂ concentrations were still at levels that pose no health threats.” S. C. Lee, Maureen Chang, Indoor Air, Volume 9, Issue 2, pages 134–138, June 1999, DOI: 10.1111/j.1600-0668.1999.t01-2-00008.x.

Effects of sustained low-level elevations of carbon dioxide on cerebral blood flow and autoregulation of the intracerebral arteries in humans – Sliwka et al. (1998) “Cerebral blood flow velocity (CBFv) was measured by insonating the middle cerebral arteries of four subjects using a 2 Mhz transcranial Doppler. Ambient CO₂ was elevated to 0.7% for 23 d in the first study and to 1.2% for 23 d in the same subjects in the second study. By non-parametric testing CBFv was elevated significantly by +35% above pre-exposure levels during the first 1-3 d at both exposure levels, after which CBFv progressively readjusted to pre-exposure levels. Despite similar CBFv responses, headache was only reported during the initial phase of exposure to 1.2% CO₂. Vascular reactivity to CO₂ assessed by rebreathing showed a similar pattern with the CBFv increases early in the exposures being greater than those elicited later. An increase in metabolic rate of the visual cortex was evoked by having the subjects open and close their eyes during a visual stimulus. Evoked CBFv responses measured in the posterior cerebral artery were also elevated in the first 1-3 d of both studies returning to pre-exposure levels as hypercapnia continued. Cerebral vascular autoregulation assessed by raising head pressure during 10 degrees head-down tilt both during the low-level exposures and during rebreathing was unaltered. There were no changes in the retinal microcirculation during serial fundoscopy studies. The time-dependent changes in CO2 vascular reactivity might be due either to retention of bicarbonate in brain extracellular fluid or to progressive increases in ventilation, or both. Cerebral vascular autoregulation appears preserved during chronic exposure to these low levels of ambient CO₂.” Sliwka U, Krasney JA, Simon SG, Schmidt P, Noth J., Aviat Space Environ Med. 1998 Mar;69(3):299-306.

Sick Building Syndrome Symptoms among the Staff in Schools and Kindergartens: are the Levels of Volatile Organic Compounds and Carbon Dioxide Responsible? – Willers et al. (1996) “From a large questionnaire-based survey investigating the indoor air quality (IAQ) in 48 schools and 74 kindergartens, 21 schools were selected for mea surements of volatile organic compounds (VOC) and carbon dioxide (CO₂) based on the prevalence of sick building syndrome (SBS) symptoms reported by the staff. The 10 schools with the lowest prevalence of SBS symptoms ‘healthy’) were compared to 11 schools with the highest prevalence (‘sick’; median value showing twice as many SBS symptoms reported). The concen trations of total VOCs (TVOC) in schools and kindergartens were low and within suggested guidelines. The levels of CO₂ were higher than suggested guidelines in several cases. However, neither TVOC nor CO₂ concentrations were associated with SBS symptoms. Thus, TVOC and CO₂ concentrations do not seem to be useful as SBS risk indicators.” Stefan Willers, Sven Andersson, Rolf Andersson, Jörgen Grantén, Christina Sverdrup, Lars Rosell, Indoor and Built Environment July 1996 vol. 5 no. 4 232-235, doi: 10.1177/1420326X9600500406.

Effects of carbon dioxide inhalation on psychomotor and mental performance during exercise and recovery – Sheehy et al. (1982) “Psychomotor and mental tests involving reaction time, rotor pursuit, short-term memory for digits and letters, and reasoning ability were administered to subjects inhaling up to 5% CO₂ in air and in gas mixtures containing 50% O₂. The psychomotor and mental tests were given during the 6 min of recovery following 10 min of treadmill running at 80% of aerobic capacity. Although the subjects inhaled the CO₂ during the entire exercise and recovery period there was no difference in performance between the CO₂ inhalation condition and the control condition for any of the performance measures.” Sheehy, J B; Kamon, E; Kiser, D., Human Factors. Vol. 24, pp. 581-588. Oct. 1982.

Effects on man of high concentrations of carbon dioxide in relation to various oxygen pressures during exposures as long as 72 hours – Consolazio et al. (1947) No abstract. W. V. Consolazio, M. B. Fisher, N. Pace, I. J. Pecora, G. C. Pitts, A. R. Behnke, American Journal of Physiology, November 1947 vol. 151 no. 2 479-503.

Increasing atmospheric CO2 and allergies

Changes in Atmospheric CO2 Influence the Allergenicity of Aspergillus fumigatus – Lang-Yona et al. (2013) “Increased susceptibility to allergies has been documented in the Western world in recent decades. However, a comprehensive understanding of its causes is not yet available. It is therefore essential to understand trends and mechanisms of allergy-inducing agents, such as fungal conidia. In this study we investigated the hypothesis that environmental conditions linked to global atmospheric changes can affect the allergenicity of Aspergillus fumigatus, a common allergenic fungal species in indoor and outdoor environments and in airborne particulate matter. We show that fungi grown under present day CO₂ levels (392 ppm) exhibit 8.5 and 3.5 fold higher allergenicity compared to fungi grown at preindustrial (280 ppm) and double (560 ppm) CO₂ levels, respectively. A corresponding trend is observed in the expression of genes encoding for known allergenic proteins and in the major allergen Asp f1 concentrations, possibly due to physiological changes such as respiration rates and the nitrogen content of the fungus, influenced by the CO₂ concentrations. Increased carbon and nitrogen levels in the growth medium also lead to a significant increase in the allergenicity. We propose that climatic changes such as increasing atmospheric CO₂ levels and changes in the fungal growth medium may impact the ability of allergenic fungi such as Aspergillus fumigatus to induce allergies.” Naama Lang-Yona, Yishai Levin, Karen C. Dannemiller, Oded Yarden, Jordan Peccia, Yinon Rudich, Global Change Biology, DOI: 10.1111/gcb.12219.

Anthropogenic climate change and allergen exposure: The role of plant biology – Ziska & Beggs (2012) “Accumulation of anthropogenic gases, particularly CO₂, is likely to have 2 fundamental effects on plant biology. The first is an indirect effect through Earth’s increasing average surface temperatures, with subsequent effects on other aspects of climate, such as rainfall and extreme weather events. The second is a direct effect caused by CO₂-induced stimulation of photosynthesis and plant growth. Both effects are likely to alter a number of fundamental aspects of plant biology and human health, including aerobiology and allergic diseases, respectively. This review highlights the current and projected effect of increasing CO₂ and climate change in the context of plants and allergen exposure, emphasizing direct effects on plant physiologic parameters (eg, pollen production) and indirect effects (eg, fungal sporulation) related to diverse biotic and abiotic interactions. Overall, the review assumes that future global mitigation efforts will be limited and suggests a number of key research areas that will assist in adapting to the ongoing challenges to public health associated with increased allergen exposure.” Lewis H. Ziska, Paul J. Beggs, Journal of Allergy and Clinical Immunology, Volume 129, Issue 1, January 2012, Pages 27–32, http://dx.doi.org/10.1016/j.jaci.2011.10.032.

Elevated atmospheric carbon dioxide concentrations amplify Alternaria alternata sporulation and total antigen production – Wolf et al. (2010) “BACKGROUND: Although the effect of elevated carbon dioxide (CO2) concentration on pollen production has been established in some plant species, impacts on fungal sporulation and antigen production have not been elucidated. OBJECTIVE: Our purpose was to examine the effects of rising atmospheric CO2 concentrations on the quantity and quality of fungal spores produced on timothy (Phleum pratense) leaves. METHODS: Timothy plants were grown at four CO2 concentrations (300, 400, 500, and 600 micromol/mol). Leaves were used as growth substrate for Alternaria alternata and Cladosporium phlei. The spore abundance produced by both fungi, as well as the size (microscopy) and antigenic protein content (ELISA) of A. alternata, were quantified. RESULTS: Leaf carbon-to-nitrogen ratio was greater at 500 and 600 micromol/mol, and leaf biomass was greater at 600 micromol/mol than at the lower CO2 concentrations. Leaf carbon-to-nitrogen ratio was positively correlated with A. alternata spore production per gram of leaf but negatively correlated with antigenic protein content per spore. At 500 and 600 micromol/mol CO2 concentrations, A. alternata produced nearly three times the number of spores and more than twice the total antigenic protein per plant than at lower concentrations. C. phlei spore production was positively correlated with leaf carbon-to-nitrogen ratio, but overall spore production was much lower than in A. alternata, and total per-plant production did not vary among CO2 concentrations. CONCLUSIONS: Elevated CO2 concentrations often increase plant leaf biomass and carbon-to-nitrogen ratio. Here we demonstrate for the first time that these leaf changes are associated with increased spore production by A. alternata, a ubiquitous allergenic fungus. This response may contribute to the increasing prevalence of allergies and asthma.” Wolf J, O’Neill NR, Rogers CA, Muilenberg ML, Ziska LH., Environ Health Perspect. 2010 Sep;118(9):1223-8. doi: 10.1289/ehp.0901867. [Full text]

Impacts of climate change on plant food allergens: a previously unrecognized threat to human health – Beggs & Walczyk (2008) “Global climate change has had, and will continue to have, many significant impacts on biological and human systems. There are now many studies of climate change impacts on aeroallergens, particularly pollen, including a study demonstrating significant increases in the major allergen content of ragweed pollen as a function of rising atmospheric carbon dioxide concentration ([CO₂]). Recent research has also demonstrated more allergenic poison ivy in response to elevated [CO₂]. Here, we suggest, for the first time, the potential for global climate change, and, in particular, increased [CO₂] and temperature, to have an impact on the allergenicity of plant food allergens such as peanut. Such impacts could have significant impacts on associated allergic diseases, and pose a previously unrecognized threat to human health. There is an urgent need for research on the impacts of climate change on plant food allergens.” Paul John Beggs, Nicole Ewa Walczyk, Air Quality, Atmosphere & Health, October 2008, Volume 1, Issue 2, pp 119-123, DOI: 10.1007/s11869-008-0013-z. [Full text]

Pollen production by Pinus taeda growing in elevated atmospheric CO₂ – Ladeau & Clark (2006) “Rising concentrations of atmospheric CO₂ may have important consequences for reproductive allocation in forest trees. Changes in pollen production could influence population dynamics and is likely to have important consequences for human health. This is the first study to evaluate pollen production by forest trees in response to rising atmospheric CO₂. Our research objective was to quantify pollen production by Loblolly Pine (Pinus taeda L.) trees growing in elevated CO₂ (ambient + 200 µl l⁻¹) since 1996. Trees grown in high-CO₂ plots first began producing pollen while younger and at smaller sizes relative to ambient-grown trees. Pollen cone and airborne pollen grain abundances were significantly greater in the fumigated stands. We conclude that the greater number of mature trees in high-CO₂ plots resulted in greater pollen production at the stand level. Precocious pollen production has important implications for fertilization and pollen dispersal from young, dense stands. Increasing levels of airborne pollen raise concerns for escalating rates of human respiratory disease.” S. L. Ladeau, J. S. Clark, Functional Ecology, Volume 20, Issue 3, pages 541–547, June 2006, DOI: 10.1111/j.1365-2435.2006.01133.x. [Full text]

Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO₂ – Mohan et al. (2006) “Contact with poison ivy (Toxicodendron radicans) is one of the most widely reported ailments at poison centers in the United States, and this plant has been introduced throughout the world, where it occurs with other allergenic members of the cashew family (Anacardiaceae). Approximately 80% of humans develop dermatitis upon exposure to the carbon-based active compound, urushiol. It is not known how poison ivy might respond to increasing concentrations of atmospheric carbon dioxide (CO₂), but previous work done in controlled growth chambers shows that other vines exhibit large growth enhancement from elevated CO₂. Rising CO₂ is potentially responsible for the increased vine abundance that is inhibiting forest regeneration and increasing tree mortality around the world. In this 6-year study at the Duke University Free-Air CO₂ Enrichment experiment, we show that elevated atmospheric CO₂ in an intact forest ecosystem increases photosynthesis, water use efficiency, growth, and population biomass of poison ivy. The CO₂ growth stimulation exceeds that of most other woody species. Furthermore, high-CO₂ plants produce a more allergenic form of urushiol. Our results indicate that Toxicodendron taxa will become more abundant and more “toxic” in the future, potentially affecting global forest dynamics and human health.” Jacqueline E. Mohan, Lewis H. Ziska, William H. Schlesinger, Richard B. Thomas, Richard C. Sicher, Kate George, and James S. Clark, PNAS June 13, 2006 vol. 103 no. 24 9086-9089, doi: 10.1073/pnas.0602392103. [Full text]

Increasing Amb a 1 content in common ragweed (Ambrosia artemisiifolia) pollen as a function of rising atmospheric CO2 concentration – Singer et al. (2005) “Although the impact of increasing atmospheric carbon dioxide concentration ([CO₂]) on production of common ragweed (Ambrosia artemisiifolia L.) pollen has been examined in both indoor and outdoor experiments, the relationship between allergen expression and [CO₂] is not known. An enzyme-linked immunosorbent assay (ELISA) was used to quantify Amb a 1, ragweed’s major allergen, in protein extracted from pollen of A. artemisiifolia grown at different [CO₂] values in a previous experiment. The concentrations used approximated atmospheric pre-industrial conditions (i.e. at the end of the 19th century), current conditions, and the CO₂ concentration projected for the middle of the 21st century (280, 370 and 600 μmol mol^–1 CO₂, respectively). Although total pollen protein remained unchanged, significant increases in Amb a 1 allergen were observed between pre-industrial and projected future [CO₂] and between current and projected future [CO₂] (1.8 and 1.6 times, respectively). These data suggest that recent and projected increases in [CO₂] could directly increase the allergenicity of ragweed pollen and consequently the prevalence and / or severity of seasonal allergic disease. However, genetic and abiotic factors governing allergen expression will need to be better established to fully understand these data and their implications for public health.” Ben D. Singer A C, Lewis H. Ziska B D, David A. Frenz C, Dennis E. Gebhard C, James G. Straka, Functional Plant Biology 32(7) 667–670, http://dx.doi.org/10.1071/FP05039. [Full text]

Production of allergenic pollen by ragweed (Ambrosia artemisiifolia L.) is increased in CO₂-enriched atmospheres – Wayne et al. (2002) “Background: The potential effects of global climate change on allergenic pollen production are still poorly understood. Objective: To study the direct impact of rising atmospheric CO₂ concentrations on ragweed (Ambrosia artemisiifolia L.) pollen production and growth. Methods: In environmentally controlled greenhouses, stands of ragweed plants were grown from seed through flowering stages at both ambient and twice-ambient CO₂ levels (350 vs 700 μL L⁻¹). Outcome measures included stand-level total pollen production and end-of-season measures of plant mass, height, and seed production. Results: A doubling of the atmospheric CO₂ concentration stimulated ragweed-pollen production by 61% (P = 0.005). Conclusions: These results suggest that there may be significant increases in exposure to allergenic pollen under the present scenarios of global warming. Further studies may enable public health groups to more accurately evaluate the future risks of hay fever and respiratory diseases (eg, asthma) exacerbated by allergenic pollen, and to develop strategies to mitigate them.” Peter Wayne, Susannah Foster, John Connolly, Fakhri Bazzaz, Paul Epstein, Annals of Allergy, Asthma & Immunology, Volume 88, Issue 3, March 2002, Pages 279–282, http://dx.doi.org/10.1016/S1081-1206(10)62009-1. [Full text]

Rising CO2 and pollen production of common ragweed (Ambrosia artemisiifolia L.), a known allergy-inducing species: implications for public health – Ziska & Caulfield (2000) “Although environmental factors such as precipitation and temperature are recognized as influencing pollen production, the impact of rising atmospheric carbon dioxide concentration ([CO₂]) on the potential growth and pollen production of hay-fever-inducing plants is unknown. Here we present measurements of growth and pollen production of common ragweed (Ambrosia artemisiifolia L.) from pre-industrial [CO₂] (280 mol mol^–1) to current concentrations (370 mol mol^–1) to a projected 21st century concentration (600 mol mol^–1). We found that exposure to current and elevated [CO₂] increased ragweed pollen production by 131 and 320%, respectively, compared to plants grown at pre-industrial [CO₂]. The observed stimulations of pollen production from the pre-industrial [CO₂] were due to an increase in the number (at 370 mol mol^–1) and number and size (at 600 mol mol^–1) of floral spikes. Overall, floral weight as a percentage of total plant weight decreased (from 21% to 13%), while investment in pollen increased (from 3.6 to 6%) between 280 and 600 mol mol^–1 CO₂. Our results suggest that the continuing increase in atmospheric [CO₂] could directly influence public health by stimulating the growth and pollen production of allergy-inducing species such as ragweed.” Lewis H. Ziska and Frances A. Caulfield, Australian Journal of Plant Physiology 27(10) 893 – 898, doi:10.1071/PP00032. [Full text]

Increased levels of airborne fungal spores in response to Populus tremuloides grown under elevated atmospheric CO₂ – Klironomos et al. (1997) “Soil fungi are important components of terrestrial ecosystems. They function as decomposers, pathogens, parasites, and mutualistic symbionts. Their main mode of dispersal is to liberate spores into the atmosphere. In this study we tested the hypothesis that a higher atmospheric CO₂ concentration will induce greater sporulation in common soil fungi, leading to higher concentrations of fungal propagules in the atmosphere. In our field experiment, the concentration of airborne fungal propagules, mostly spores, increased fourfold under twice-ambient CO₂ concentrations. Analysis of decomposing leaf litter (likely the main source of airborne fungal propagules) indicated that the fungi produced fivefold more spores under elevated CO₂. Our results provide evidence that elevations in atmospheric CO₂ concentration can directly affect microbial function, which may have important implications for litter decay, fungal dispersal, and human respiratory health. Key words: atmospheric CO₂, fungal spores, global change, Populus tremuloides.” John N. Klironomos, Matthias C. Rillig, Michael F. Allen, Donald R. Zak, Kurt S. Pregitzer, Mark E. Kubiske, Canadian Journal of Botany, 1997, 75(10): 1670-1673, 10.1139/b97-880.

Extreme carbon dioxide events

This section lists papers on some extreme events where carbon dioxide has caused deaths or serious harm. It should be noted that this is not very relevant to the carbon dioxide levels associated with current global warming. However, for some carbon capture and storage scenarios these events serve as practical examples to what happens during high local carbon dioxide levels.

Non-volcanic CO₂ Earth degassing: Case of Mefite d’Ansanto (southern Apennines), Italy – Chiodini et al. (2010) “Mefite d’Ansanto, southern Apennines, Italy is the largest natural emission of low temperature CO₂ rich gases, from non-volcanic environment, ever measured in the Earth. The emission is fed by a buried reservoir, made up of permeable limestones and covered by clayey sediments. We estimated a total gas flux of ~2000 tons per day. Under low wind conditions, the gas flows along a narrow natural channel producing a persistent gas river which has killed over a period of time people and animals. The application of a physical numerical model allowed us to define the zones which potentially can be affected by dangerous CO₂ concentration at breathing height for humans.” Chiodini, G., D. Granieri, R. Avino, S. Caliro, A. Costa, C. Minopoli, and G. Vilardo (2010), Geophys. Res. Lett., 37, L11303, doi:10.1029/2010GL042858.

Asphyxiation Due to Dry Ice in a Walk-in Freezer – Dunford et al. (2009) “Background: Exposure to a high concentration of environmental carbon dioxide (CO₂) can result in poisoning through direct toxicity and by displacing atmospheric oxygen (O₂). Dry ice undergoes sublimation to a gaseous state at −78.5°C (−109.3°F), which is heavier than air and can accumulate in dependent areas. Case Report: We report the case of a 59-year-old man found in cardiac arrest shortly after entering a recently repaired walk-in freezer that contained dry ice. First responders and bystanders did not recognize the proximate hazardous environment but were fortunately uninjured. A careful Emergency Department history coupled with rapid case investigation by the Medical Examiner’s Office led to the determination of the cause of death and the elimination of the ongoing hazard. Conclusion: This case illustrates the lethal consequences of improper storage of dry ice and the need to consider toxic environmental exposure as a cause of sudden cardiac arrest.” James V. Dunford, Jon Lucas, Nick Vent, Richard F. Clark, F. Lee Cantrell, The Journal of Emergency Medicine, Volume 36, Issue 4, May 2009, Pages 353-356, doi:10.1016/j.jemermed.2008.02.051.

A Carbon Dioxide Fatality from Dry Ice – Srisont et al. (2009) “This report documents a rare case of carbon dioxide intoxication in a young healthy male. The deceased hid in a small plastic container, size 1.5 × 1 × 1 m, and within 5 min he was located suffering convulsions and was reported as dead within minutes. Scene investigation revealed dry ice in the container. Autopsy findings were unremarkable. The probable cause of the convulsions was carbon dioxide intoxication due to both the dry ice sublimation and the small confined space in which he was hiding. This report emphasizes the significance of scene investigation in establishing the cause of the death.” Smith Srisont, Thamrong Chirachariyavej, A. V. M. Vichan Peonim, Journal of Forensic Sciences, Volume 54, Issue 4, pages 961–962, July 2009, DOI: 10.1111/j.1556-4029.2009.01057.x. [Full text]

A shallow-layer model for heavy gas dispersion from natural sources: Application and hazard assessment at Caldara di Manziana, Italy – Costa et al. (2008) “Several nonvolcanic sources in central Italy emit a large amount of carbon dioxide (CO₂). Under stable atmospheric conditions and/or in the presence of topographic depressions, the concentration of CO₂, which has a molecular mass greater than that of air, can reach high values that are lethal to humans or animals. Several episodes of this phenomenon were recorded in central Italy and elsewhere. In order to validate a model for the dispersion of a heavy gas and to assess the consequent hazard, we applied and tested the code TWODEE-2, an improved version of the established TWODEE model, which is based on a shallow-layer approach that uses depth-averaged variables to describe the flow behavior of dense gas over complex topography. We present results for a vented CO₂ release at Caldara di Manziana in central Italy. We find that the model gives reliable results when the input quantity can be properly defined. Moreover, we show that the model can be a useful tool for gas hazard assessment by evaluating where and when lethal concentrations for humans and animals are reached.” Costa, A., G. Chiodini, D. Granieri, A. Folch, R. K. S. Hankin, S. Caliro, R. Avino, and C. Cardellini (2008), Geochem. Geophys. Geosyst., 9, Q03002, doi:10.1029/2007GC001762. [Full text]

Degassing Lakes Nyos and Monoun: Defusing certain disaster – Kling et al. (2005) “Since the catastrophic releases of CO₂ in the 1980s, Lakes Nyos and Monoun in Cameroon experienced CO₂ recharge at alarming rates of up to 80 mol/m² per yr. Total gas pressures reached 8.3 and 15.6 bar in Monoun (2003) and Nyos (2001), respectively, resulting in gas saturation levels up to 97%. These natural hazards are distinguished by the potential for mitigation to prevent future disasters. Controlled degassing was initiated at Nyos (2001) and Monoun (2003) amid speculation it could inadvertently destabilize the lakes and trigger another gas burst. Our measurements indicate that water column structure has not been compromised by the degassing and local stability is increasing in the zones of degassing. Furthermore, gas content has been reduced in the lakes ≈12-14%. However, as gas is removed, the pressure at pipe inlets is reduced, and the removal rate will decrease over time. Based on 12 years of limnological measurements we developed a model of future removal rates and gas inventory, which predicts that in Monoun the current pipe will remove ≈30% of the gas remaining before the natural gas recharge balances the removal rate. In Nyos the single pipe will remove ≈25% of the gas remaining by 2015; this slow removal extends the present risk to local populations. More pipes and continued vigilance are required to reduce the risk of repeat disasters. Our model indicates that 75-99% of the gas remaining would be removed by 2010 with two pipes in Monoun and five pipes in Nyos, substantially reducing the risks.” George W. Kling, William C. Evans, Greg Tanyileke, Minoru Kusakabe, Takeshi Ohba, Yutaka Yoshida, and Joseph V. Hell, PNAS October 4, 2005 vol. 102 no. 40 14185-14190, doi: 10.1073/pnas.0502274102. [Full text]

Recent pH and CO2 profiles at Lakes Nyos and Monoun, Cameroon: implications for the degassing strategy and its numerical simulation – Kusakabe et al. (2000) “In situ pH profiles are reported for the first time for Lakes Nyos and Monoun. The pH profiles were converted to CO2 profiles using HCO3− profiles calculated from conductivity data. Recent observations (1993–1996) at Lake Nyos indicates that CO2 still accumulates below 180 m depth at a rate of 125 Mmol year−1. At Lake Monoun, the majority of CO2 is present below a depth of 60 m, only 25 m below the saturation depth. Consequently, a potential danger of gas explosion is high at both lakes, and artificial degassing of the lakes should be performed as soon as possible. A system for industrial degassing of the lakes is proposed. The system, based on the self-sustained gas lift principle, consists of multiple pipes (14 cm in diameter) with different intake depths; 12 pipes for Lake Nyos (four each at 185, 195 and 205 m) and three pipes for Lake Monoun (at 70, 80 and 90 m). The stepped degassing at different depths is intended to keep the maximum stability of the lakes. The proposed degassing operation was simulated using the dyresm code for both lakes. In 5 years, approximately 50% of currently dissolved CO2 in Lake Nyos and 90% in Lake Monoun will be removed. The expected changes in the thermal and chemical structures of the lakes as degassing proceeds will be most easily monitored with a carefully calibrated CTD equipped with a pH sensor. The simulation indicates that the discharged degassed water will sink to a level of neutral buoyancy, i.e. to a maximum of 70 m at Lake Nyos and 35 m at Lake Monoun. There would be no possibility of triggering a gas explosion by this plunge of discharged water because the water present there would have already been replaced by water at lower CO2 concentration, during the degassing from shallower pipes.” M Kusakabe, G.Z Tanyileke, S.A McCord, S.G Schladow, Journal of Volcanology and Geothermal Research, Volume 97, Issues 1-4, April 2000, Pages 241-260, doi:10.1016/S0377-0273(99)00170-5.

Possible asphyxiation from carbon dioxide of a cross-country skier in eastern California: a deadly volcanic hazard – Hill (2000) “This report describes an incident in which exceedingly high levels of carbon dioxide may have contributed to the death of a skier in eastern California. A cross-country skier was found dead inside a large, mostly covered snow cave, 1 day after he was reported missing. The autopsy report suggests that the skier died of acute pulmonary edema consistent with asphyxiation; carbon dioxide measurements inside the hole in which he was found reached 70%. This area is known for having a high carbon dioxide flux attributed to degassing of a large body of magma (molten rock) 10 to 20 km beneath the ski area. The literature describes many incidents of fatal carbon dioxide exposures associated with volcanic systems in other parts of the world. We believe this case represents the first reported death associated with volcanically produced carbon dioxide in the United States. Disaster and wilderness medicine specialists should be aware of and plan for this potential health hazard associated with active volcanoes.” Peter M. Hill, Wilderness & Environmental Medicine, Volume 11, Issue 3, September 2000, Pages 192-195, doi:10.1580/1080-6032(2000)011[0192:PAFCDO]2.3.CO;2.

Fatal intoxication due to an unexpected presence of carbon dioxide – Guillemin & Horisberger (1994) “A fatal accident which occurred in a tank containing a sludge made of wine and activated charcoal is described. Similar accidents in the wine industry seem to have never been reported before. Initially, the cause of death was not obvious and became clear only after the autopsy confirmed the presence of a very high concentration of carbon dioxide in blood. It is shown in this paper how the concentration of carbon dioxide in the tank could be estimated from its solubility in water, assuming a realistic content of this gas in the wine remaining in the sludge. Moreover the accident was analysed by the fault tree method which revealed that, as well as the deficiencies in risk management of such companies, the unsuspected presence of carbon dioxide played a significant role.” Michel P. Guillemin and B. Horisberger, Ann Occup Hyg (1994) 38 (6): 951-957. doi: 10.1093/annhyg/38.6.951.

CO₂-rich gases from Lakes Nyos and Monoun, Cameroon; Laacher See, Germany; Dieng, Indonesia, and Mt. Gambier, Australia—variations on a common theme – Giggenbach et al. (1991) “Helium (RA = 3.0 to 5.6) and carbon (δ13C from −7.2 to −3.4‰) isotopic compositions, and relative CO₂, CH₄, N₂, He and Ar contents of CO₂-rich gases from Lakes Nyos and Monoun, Cameroon; Laacher See, Germany; Dieng Volcanic Plateau, Indonesia, and a well at Mt. Gambier, Australia, point to a common, essentially magmatic origin. … Otherwise, gas may accumulate to form a stable pocket (Mt. Gambier). Minor leakage from such pockets may lead to surface discharges of CO₂-rich gases as at Laacher See, re-absorption into shallow groundwater to the formation of the low-salinity, CO₂-charged waters encountered at Lakes Nyos and Monoun. The occurrence of these high-CO₂, low-temperature systems is likely to be favored in tectonically active regions, allowing deep, possibly mantle gases to rise, but with sufficiently low regional heat flows to prevent the establishment of large-scale geothermal activity.” W.F. Giggenbach, Y. Sano, H.U. Schmincke, Journal of Volcanology and Geothermal Research, Volume 45, Issues 3-4, April 1991, Pages 311-323, doi:10.1016/0377-0273(91)90065-8.

Water and gas chemistry of Lake Nyos and its bearing on the eruptive process – W.F. Giggenbach (1990) “The isotopic and chemical composition of water samples collected from Lake Nyos some two and eight weeks after the eruption of August 21, 1986 point to the existence of three distinct mixing regimes involving three water components. An essentially homogeneous, unmixed body of water at depths > 100 m, overlain by water increasingly affected by surface evaporation and a 5–10-m layer containing recent, but pre-eruption rain water. The cationic constituents (Na, K, Mg, Ca, Mn, Fe) of the lake water correspond to the dissolution of around 0.1 g of local rock, the waters are close to saturation with respect to siderite. The composition of the gas dissolved in the deep lake waters (0.65% b.w. of CO₂, PCO₂ = 4.4b) corresponds (in mmol mol−1) to 996 CO₂, 2.0 CH₄, 2.0 N₂, 0.05 Ar, 0.004 He, 0.0002 H₂, 0.0001 Ne, < 0.01 O₂, < 0.004 H₂S, < 0.001 CO. The isotopic compositions of CO₂ (δ¹³C = -3.4‰) and of He (R_air = 5.5) suggest deep magmatic origins, the ¹³C and ²H content of CH₄ organic sedimentary origin, the presence of aromatic hydrocarbons indicates very high temperatures of hydrocarbon formation. Exsolution of gas will first lead to the precipitation of siderite then iron hydroxide. The chemistry of the lake waters points to a loss of some 240,000 t of CO₂ from the upper 100 m of the lake, their isotopic composition is consistent with the assumption that the eruption was triggered by the accumulation of cold rain waters at the lake surface prior to the eruption inducing partial convective overturn. There is no need to invoke addition of chemical or isotopic constituents from deeper levels during the eruption.” W.F. Giggenbach, Journal of Volcanology and Geothermal Research, Volume 42, Issue 4, 15 August 1990, Pages 337-362, doi:10.1016/0377-0273(90)90031-A.

The Lake Nyos gas disaster: chemical and isotopic evidence in waters and dissolved gases from three Cameroonian crater lakes, Nyos, Monoun and Wum – Kusakabe et al. (1989) “To better understand the cause of the Nyos gas disaster of August 21, 1986, we conducted geochemical and limnological surveys in October 1986, of three lakes (Nyos, Monoun and Wum) which are located in the Cameroon volcanic zone that is characterized by a prevalence of young alkaline basalts and basanitoids. … The August 1986 gas bursts from Lake Nyos were most likely caused by rapid exsolution of dissolved CO2 within the lake; an explosive process such as a phreatic eruption or a CO₂ gas-jetting from beneath the bottom is unlikely because of low concentrations of Cl⁻ and SO₄²⁻, no oxygen isotopic shift, low turbidity, and no reported perturbation of the bottom sediments. Exsolution of CO₂ bubbles could occur if CO₂-saturated bottom water was displaced upwards by an increased influx of high salinity water from the bottom during the rainy season. Exsolution of CO₂ at the upper layers was possibly accelerated by upwelling of a two-phase fluid (CO₂ bubbles and solution), a mechanism known as a pneumatic lift pump, resulting in discharge of a large amount of CO₂ gas. The H₂S concentration in the gas cloud must have been kept far below the lethal level because of a high Fe²⁺ concentration of the lake water.” Minoru Kusakabe, Takashi Ohsumi, Shigeo Aramaki, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 167-185, doi:10.1016/0377-0273(89)90056-5.

The gas cloud of Lake Nyos (Cameroon, 1986): Results of the Italian technical mission – Barberi et al. (1989) “On August 21, 1986, a gas cloud issued from Lake Nyos in Cameroon killed over 1700 people. An Italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe. On the basis of observations and measurements in the field and of samples collected, the origin of the gas outburst is attributed to a phreatic explosion from beneath the bed of the lake. This interpretation appears to fit well the observed and reported phenomena, and seems perfectly consistent with the geological-geothermal conditions of the area.” F. Barberi, W. Chelini, G. Marinelli, M. Martini, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 125-134, doi:10.1016/0377-0273(89)90053-X.

Lake Nyos disaster, Cameroon, 1986: the medical effects of large scale emission of carbon dioxide? – Baxter et al. (1989) “Carbon dioxide was blamed for the deaths of around 1700 people in Cameroon, west Africa, in 1986 when a massive release of gas occurred from Lake Nyos, a volcanic crater lake. The clinical findings in 845 survivors seen at or admitted to hospital were compatible with exposure to an asphyxiant gas. Rescuers noted cutaneous erythema and bullae on an unknown proportion of corpses and 161 (19%) survivors treated in hospital; though these lesions were initially believed to be burns from acidic gases, further investigation suggested that they were associated with coma states caused by exposure to carbon dioxide in air. The disaster at Lake Nyos and a similar event at Lake Monoun, Cameroon, two years previously provide new information on the possible medical effects of large scale emissions of carbon dioxide, though the presence of other toxic factors in these gas releases cannot be excluded.” P. J. Baxter, M. Kapila, D. Mfonfu, BMJ 298 : 1437 doi: 10.1136/bmj.298.6685.1437 (Published 27 May 1989). [Full text]

Mechanisms of the Nyos carbon dioxide disaster and of so-called phreatic steam eruptions – Tazieff (1989) “During the night of August 21, 1986, a huge volume of concentrated CO₂ was emitted by the crater (maar) of Nyos, Cameroon. It killed more than 1700 people and all animal life as far as 14 km away. Two hypotheses have been put forward to account for this disaster. The chronologically first one imputes it to have been a phreatic eruption, exceptionally CO₂-rich, as had been the case in February 1979 on the Diëng Plateau in Central Java, Indonesia, where the erupting crater was lake-less. The second one claims a limnic origin for the CO₂ release, through an overturn of the 220 m-deep Lake Nyos, the hypolimnium of which was supposed to be oversaturated by dissolved gas of volcanic origin. The present paper points to six observed facts for which the eruptive hypothesis easily accounts, and which the authors of the limnic one do ignore.” Haroun Tazieff, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 109-116, doi:10.1016/0377-0273(89)90051-6.

Origin of carbon dioxide emanation from the 1979 Dieng eruption, Indonesia: Implications for the origin of the 1986 Nyos catastrophe – Allard et al. (1989) “In February 1979, CO₂ emanations accompanying a phreatic eruption killed 142 people at Dieng volcano, Central Java. The gas emitted was nearly pure carbon dioxide, with subordinate amounts of methane and sulfur compounds. … It is proposed that magmatic carbon dioxide, accumulated beneath the Dieng volcanic complex, was the source of the lethal gas, the effusion of which was triggered by the pressure release generated by the phreatic eruption. The total CO₂ discharge of the 1979 Dieng event might have approached 0.1 km3, i.e. close to the lower output estimated for the 1986 Nyos catastrophe. The Dieng example demonstrates that expansion and then effusion of pure magmatic carbon dioxide, accumulated at shallow levels beneath volcanoes, may account for a major hazard from phreatic eruptions, be it a trigger or only a consequence of the eruptions.” P. Allard, D. Dajlevic, C. Delarue, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 195-206, doi:10.1016/0377-0273(89)90058-9.

Medical evaluation of the victims of the 1986 Lake Nyos disaster – Wagner et al. (1988) “A cloud of carbon dioxide gas, with an estimated volume of 1 km3 was released from Lake Nyos, a volcanic crater lake in Cameroon, Africa, causing 1700 to 2000 human fatalities as well as killing thousands of livestock and wild animals. At the request of the Cameroonian Government, the Office of Foreign Disaster Assistance of the U.S. Department of State sent a multidisciplinary team which included 2 forensic pathologists to assist the Government of Cameroon in investigating this natural disaster. The medical evaluation was concentrated in 3 areas: the autopsy of human and animal fatalities, examination and interview of survivors, and examination of the scene of the disaster. Toxicologic specimens were obtained at autopsy, and numerous samples of lake water were collected. The autopsy findings were consistent with asphyxia. The results of chemical analyses excluded many volatiles but not carbon dioxide as the toxic agent. The exact source of this gas continues to be a subject of a heated geologic debate, but fermentation of organic materials in the lake water has been eliminated on the basis of C14 isotope studies. This investigation underlines the value of forensic pathologists in epidemiological studies and in the examination of living persons.” Wagner GN, Clark MA, Koenigsberg EJ, Decata SJ., J Forensic Sci. 1988 Jul;33(4):899-909.

The 1986 Lake Nyos Gas Disaster in Cameroon, West Africa – Kling et al. (1987) “The sudden, catastrophic release of gas from Lake Nyos on 21 August 1986 caused the deaths of at least 1700 people in the northwest area of Cameroon, West Africa. Chemical, isotopic, geologic, and medical evidence support the hypotheses that (i) the bulk of gas released was carbon dioxide that had been stored in the lake’s hypolimnion, (ii) the victims exposed to the gas cloud died of carbon dioxide asphyxiation, (iii) the carbon dioxide was derived from magmatic sources, and (iv) there was no significant, direct volcanic activity involved. The limnological nature of the gas release suggests that hazardous lakes may be identified and monitored and that the danger of future incidents can be reduced.” George W. Kling, Michael A. Clark, Glen N. Wagner, Harry R. Compton, Alan M. Humphrey, Joseph D. Devine, William C. Evans, John P. Lockwood, Michele L. Tuttle and Edward J. Koenigsberg, Science 10 April 1987: Vol. 236 no. 4798 pp. 169-175, DOI: 10.1126/science.236.4798.169.

Origin of the lethal gas burst from Lake Monoun, Cameroun – Sigurdsson et al. (1987) “On 15 August, 1984, a lethal gas burst issued from a submerged 96-m-deep crater in Lake Monoun in Cameroun, western Africa, killing 37 people. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. … Gases effervescing from depressurized deep waters are dominantly CO₂ with minor CH₄, having δ¹³C of −7.18 and −54.8 per mil, respectively. … The resultant ebullition of CO₂ from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high. People travelling through the gas cloud were asphyxiated, presumably from CO₂, and suffered skin discoloration from unidentified components.” H. Sigurdsson, J.D. Devine, F.M. Tchua, F.M. Presser, M.K.W. Pringle, W.C. Evans, Journal of Volcanology and Geothermal Research, Volume 31, Issues 1-2, March 1987, Pages 1-16, doi:10.1016/0377-0273(87)90002-3.

An example of health hazard: People killed by gas during a phreatic eruption: Diëng plateau (Java, Indonesia), February 20th 1979 – Le Guern et al. (1982) “On February 20th, 1979, 142 inhabitants of Dieng Plateau (Indonesia) were asphyxiated by poisonous gases during a mild phreatic eruption. From later fields gas collection and analysis, the casualties are considered to be due to CO₂ rich volcanic gases.” F. Le Guern, H. Tazieff and R. Faivre Pierret, Bulletin of Volcanology, Volume 45, Number 2, 153-156, DOI: 10.1007/BF02600430.