Carbon Dioxide (CO₂)

Properties

Exposure Effects

Existing Guidelines

Volcanic Examples and Incidents

References

Volcanic Gases and Aerosols Index

Properties

Carbon dioxide (CO₂) is a colourless and odourless gas. It is non-flammable and chemically non-reactive (Sax and Lewis, 1989). CO₂ is 1.5 times as heavy as air (its density is 1.80 g L^-1 at 25°C and 1 atm (Lide, 2003)) and, if it is emitted slowly, flows down-slope and may accumulate at low elevations. Concentration ranges of CO₂ in dilute volcanic plumes can range from 1 ppm to hundreds of ppm above the tropospheric background of ~360 ppm (T. Elias pers. comm.; Oppenheimer et al., 1998), and the gas has a residence times in the lower atmosphere of approximately 4 years (Brimblecombe, 1996).

Due to the high levels of CO₂ required to cause harm, concentrations of CO₂ are often expressed as a percentage of the gas in air by volume (1% = 10,000 ppmv). This is in contrast to other volcanic gases.

Exposure Effects

Carbon dioxide (CO₂) is a toxic gas at high concentration, as well as an asphyxiant gas (due to reduction in oxygen). Irritation of the eyes, nose and throat occurs only at high concentrations. The concentration thresholds for health effects are outlined in the table.

Health effects of respiratory exposure to carbon dioxide
(Baxter, 2000; Faivre-Pierret and Le Guern, 1983 and refs therein; NIOSH, 1981).

Existing Guidelines

Gas masks may be of limited use in high CO₂ concentrations due to the lack of oxygen. Hence it has been recommended that working or living areas should be immediately evacuated when concentrations exceed 1.5% by volume (the occupational short-term exposure limit value). Ambient guidelines for CO₂ do not exist. Occupational guidelines for CO₂ concentrations are given in the table.

Occupational guidelines for CO₂
(Concentration of 1% = 10000 ppm)

• ppm by volume at 25ºC and 760 torr.

1. http://europa.eu.int/comm/employment_social/health_safety/docs/oels_en.pdf
2. HSE, 2002. Occupational Exposure Limits 2002. HSE Books, Sudbury.
3. NIOSH Pocket Guide to Chemical Hazards (NPG). http://www.cdc.gov/niosh/npg/npg.html
4. OSHA Standards Website

Volcanic Examples and Incidents

Carbon dioxide (CO₂) release during eruptions and from vents, the ground, and lava flows can pose a hazard where concentrations are very high and the gas is trapped near the surface. Emissions are most dangerous where they can build up in confined spaces such as natural topographic depressions, excavations and pits, or building basements and cupboards, and Le Guern et al., (1982) proposed that areas located down-slope from old fissures are of particularly high risk. Deaths from increased CO2 concentrations have been reported at Vestmannaeyjar on Heimaey (during the 1973 Eldfell eruption); Vulcano, Italy; Mammoth Mountain, USA and Nyiragongo, DR Congo amongst others (see table). The three events that dominate the CO₂ casualty list are the gas-outbursts of Lake Nyos and Lake Manoun, Cameroon and the gas cloud emission at Dieng. Although the two lake outbursts are frequently quoted in volcanic literature, their initiation is thought to be unrelated to volcanic activity at the time. The phreatic eruption on the Dieng Plateau, Indonesia in 1979, was the worst CO₂ related tragedy not associated with lake-overturn. This eruption released a cloud of CO₂ that overwhelmed ~142 villagers trying to escape from the area and claimed more lives when people tried to rescue the bodies. Gases sampled at the active fissure shortly afterward contained CO₂ concentrations of 98-99% (Le Guern et al., 1982). The 18 April 1906 eruption of Vesuvius, Italy is also implicated in a CO₂ related death: Perret (1924) recorded that CO₂ from the eruption rendered the air "almost irrespirable" and, along with fine ash, blames it for the death of a 19 year old who had a recent history of bronchitis. Gas following major gullies on the west flank of Concepción, Costa Rica during its eruptive activity in 1986 resulted in sore throats and drowsiness and was tentatively thought to be CO₂ (Smithsonian Institution, 1986). In Indonesia, CO₂ clouds have been reported to flow down the slopes of Tangkubanparahu volcano, sometimes killing children (Le Guern et al., 1982).

Ground emissions of CO₂ are particularly hazardous, as there is often little warning of high concentrations:

• Nyiragongo, DR Congo: During the 2002 eruption, measured CO₂ concentrations in some locations ranged from 20-30% up to 90%, well above the lethal concentration. These ground CO₂ emanations were called mazuku or "evil winds" by the population and pockets of the gas were found to reach heights of up to 40 m. In the years prior to the eruption, ground emissions of CO₂ in the Goma and Lake Kivu area were probably responsible for a number of fatalities (Baxter and Ancia, 2002).
• Vulcano, Italy: During the 1980s, CO₂ emissions were responsible for occasional deaths of animals (rabbits, goats) and of two children (Baubron et al., 1990). In 1988, measurements of CO₂ at Vulcano - an area densely inhabited during the summer - revealed that concentrations in the ground and in water wells around the volcano, were high enough to be a health hazard and in some locations emissions were nearly 100%. The maximum concentrations were found in a campsite and, following transmission of this data to local authorities, camping around the cone was stopped.

Soil gas emissions of CO₂ pose a hazard to workers and residents in volcanic and geothermal areas, due to their diffusion and accumulation in confined locations:

• Mammoth Mountain, USA: A number of cases of near asphyxia have been reported by people entering small snow-covered cabins in the Mammoth Mountain area (Farrar et al., 1995; Sorey et al., 1998) and the death of a cross-country skier in a snow well in 1998 is thought to have been caused by asphyxia (Hill, 2000). CO₂ concentrations measured in the well two days after the body was discovered were 70%. Lethal concentrations were also found in a cabin and vault near Horseshoe Lake on the mountain, and a campground in the area was consequently closed for overnight use (Farrar et al., 1995).
• Kilauea Volcano, Hawaii: Measurements in summit lava tubes show CO₂ concentrations up to 1%, well above the occupational TWA standard, and volcano speleologists have reported mental confusion and exhaustion whilst mapping these tubes. CO₂ excursions measured in the entrance to a seismic vault located just below ground surface have been as high as 0.5% (USGS, Hawaiian Volcano Observatory, unpublished data).
• Furnas, Azores: In Furnas Caldera, levels of CO₂ measured in the soil range from background (<1.5%) to 100%. About one-third of the houses in Furnas village, located in the caldera, were sited in areas of elevated CO₂ soil degassing in 1993. Unventilated, confined spaces in some houses contained levels of CO₂ that could cause asphyxiation and observations suggested that large and potential lethal surges of CO₂ could occur without warning (Baxter et al., 1999).
• Rotorua, New Zealand: High levels of CO₂ have been found in buildings in Rotorua, which is located on an active geothermal area. Here, indoor ambient concentrations can reach 2%, and closer to venting areas, 15% (Durand and Scott, 2003).
• Alban Hills Volcanic District, Italy: Elevated CO₂ concentrations have been linked to the death of at least 10 people in the central Italian region of Lazio over the last 20 years (Beaubien et al., 2003). The CO₂ asphyxiation of 29 cows in a heavily populated area near Rome in September 1999 prompted soil-gas studies to examine the distribution of the local health risk (Beaubien et al., 2003, Carapezza et al., 2003). The studies found that CO₂ concentrations at 1.5 m height above the ground in a residential area on the northwestern flank of the Alban Hills episodically exceeded the occupational threshold of 0.5%. At 0.75 m height, 0.3-0.5% was frequently exceeded (Carapezza et al., 2003), suggesting an increased hazard to children.

Mortality and morbidity incidents associated with volcanic CO₂ emissions

References

Baubron, J.C., Allard, P. and Toutain, J.P., 1990. Diffuse volcanic emissions of carbon dioxide from Vulcano Island, Italy. Nature, 344: 51-53.

Baxter, P.J., 2000. Gases. In: P.J. Baxter, P.H. Adams, T.-C. Aw, A. Cockcroft and J.M. Harrington (Editors), Hunter's Diseases of Occupations. Arnold, London, pp. 123-178.

Baxter, P.J. and Ancia, A., 2002. Human health and vulnerability in the Nyiragongo volcano crisis Democratic Republic of Congo 2002: Final Report to the World Health Organisation, World Health Organisation.

Baxter, P.J., Baubron, J.-C. and Coutinho, R., 1999. Health hazards and disaster potential of ground gas emissions at Furnas volcano, Sao Miguel, Azores. Journal of Volcanology and Geothermal Research, 92(1-2): 95-106.

Beaubien, S.E., Ciotoli, G. and Lombardi, S., 2003. Carbon dioxide and radon gas hazard in the Alban Hills area (central Italy). Journal of Volcanology and Geothermal Research, 123(1-2): 63-80.

Brimblecombe, P., 1996. Air Composition and Chemistry. Cambridge University Press, Cambridge.

Carapezza, M.L., Badalamenti, B., Cavarra, L. and Scalzo, A., 2003. Gas hazard assessment in a densely inhabited area of Colli Albani Volcano (Cava dei Selci, Roma). Journal of Volcanology and Geothermal Research, 123(1-2): 81-94.

Cronin, S.J. and Sharp, D.S., 2002. Environmental impacts on health from continuous volcanic activity at Yasur (Tanna) and Ambrym, Vanuatu. International Journal of Environmental Health Research, 12: 109-123.

Durand, M. and Scott, B.J., 2003. An investigation of geothermal soil gas emissions and indoor air pollution in selected Rotorua buildings, Institute of Geological & Nuclear Sciences Science Report 2003/28.

Faive-Pierret, R. and Le Guern, F., 1983. Health risks linked with inhalation of volcanic gases and aerosols. In: H. Tazieff and J.C. Sabroux (Editors), Forecasting Volcanic Events. Elsevier Science Publishers B.V., Amsterdam, pp. 69-81.

Farrar, C.D., Sorey, M.L., Evans, W.C., Howle, J.F., Kerr, B.D., Kennedy, B.M., King, C.-Y. and Southon, J.R., 1995. Forest-killing diffuse CO2 emission at Mammoth Mountain as a sign of magmatic unrest. Nature, 376: 675-678.

Hayakawa, Y., 1999. Catalog of volcanic eruptions during the past 2000 years in Japan. Journal of Geography, 108(4): 472-488.

Hill, P.M., 2000. Possible asphyxiation from carbon dioxide of a cross-country skier in eastern California: a deadly volcanic hazard. Wilderness and Environmental Medicine, 11: 192-195.

Itikarai, I. and Stewart, R., 1993, Rabual: in Annual report of the world volcanic eruptions, in 1990, Bulletin of Volcanic Eruptions (BVE). 30: 103-104.

Le Guern, F., Tazieff, H. and Faivre-Pierret, R., 1982. An example of health hazard: people killed by gas during a phreatic eruption: Dieng Plateau (Java, Indonesia), February 20th 1979. Bulletin Volcanologique, 45(2): 153-156.

Lide, D.R. (Ed.), 2003. CRC Handbook of Chemistry and Physics, 84th edn. CRC Press. Boca Raton, Florida.

National Institute for Occupational Safety and Health (NIOSH), 1981. Occupational Health Guidelines for Chemical Hazards, DHHS (NIOSH) Publication No. 81-123. http://www.cdc.gov/niosh/81-123.html.

Oppenheimer, C., Francis, P., Burton, M., Maciejewski, A.J.H. and Boardman, L., 1998. Remote measurement of volcanic gases by Fourier transform infrared spectroscopy. Applied Physics B, 67: 505-515.

Othman-Chande, M., 1987. The Cameroon volcanic gas disaster: An analysis of a makeshift response. Disasters, 11(2): 96-101.
Perret, F.A., 1924. The Vesuvius eruption of 1906: study of a volcanic cycle. The Carnegie Institution of Washington, 151 pp.

Sax, N.I. and Lewis, R.J., Sr., 1989. Dangerous Properties of Industrial Materials, 7th edn. Van Nostrand Reinhold. New York.

Sigurdsson, H., Devine, J.D., Tchoua, F.M., Presser, T.S., Pringle, M.K.W. and Evans, W.C., 1987. Origin of the lethal gas burst from Lake Monoun, Cameroun. Journal of Volcanology and Geothermal Research, 31(1-2): 1-16.

Smithsonian Institution, 1979. Dieng Volcanic Complex. Scientific Event Alert Network (SEAN) Bulletin, vol. 4, no. 2.

Smithsonian Institution, 1986. Concepcion. Scientific Event Alert Network (SEAN) Bulletin v. 11, no. 5.

Smithsonian Institution, 2002. Nyiragongo. Bulletin of the Global Volcanism Network (BGVN), v. 27, no. 4.

Sorey, M.L., Evans, W.C., Kennedy, B.M., Farrar, C.D., Hainsworth, L.J. and Hausback, B., 1998. Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California. Journal of Geophysical Research, 103(B7): 15,303-15,323.

Thorarinsson, S., 1979. On the damage caused by volcanic eruptions with special reference to tephra and gases. In: P.D. Sheets and D.K. Grayson (Editors), Volcanic Activity and Human Ecology. Academic Press Inc., New York and London, pp. 125-159.