Chapter 57 Hazards of Volcanic Gases Glyn Williams-Jones Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada Hazel Rymer Faculty of Science, The Open University, Walton Hall, Milton Keynes, UK Chapter Outline 3.3. H2S Hazards 990 1. Introduction 985 3.4. HCl Hazards 990 2. Toxicity of Volcanic Gas Species 985 3.5. HF Hazards 990 3. Hazards to Population and the Environment: 4. Gas Hazard Mitigation 991 Case Studies 987 5. Summary 991 3.1. CO2 Hazards 988 Further Reading 991 3.2. SO2 Hazards 989 GLOSSARY hazardous and responsible for deaths every year. They have an important effect on the regional and global environment aerosol A colloidal dispersion of liquid particles in a gas, e.g., SO2, and may contribute greenhouse gases to the atmosphere. which will react with the OH radical in the atmosphere to form Indirectly, through the destruction of crops, volcanic gas tiny droplets of sulfuric acid (H2SO4). hazard In a volcanic context, hazard refers to the phenomena pro- emissions have resulted in starvation and disease (40% of duced by a volcanic event and is directly related to Risk, where volcano-related deaths between 1600 and 1982). Risk ¼ Hazard  Vulnerability, with vulnerability referring to the The composition of volcanic gases depends on the type consequences for population and infrastructure. of volcano and its eruptive state. However, the most com- PEL The recommended permissible exposure limit to a given mon volcanic gases in order of abundance are water (H2O, chemical compound above which health risks may occur. The 30e90 mol%), carbon dioxide (CO2,5e40 mol%), sulfur exposure limit is generally averaged over an 8-h day, 40-h week. It dioxide (SO2,5e50 mol %), hydrogen (H2, <2 mol%), is measured in parts of compound (e.g., CO ) per million parts of 2 hydrogen sulfide (H2S, <2 mol%), and carbon monoxide air (ppm). (CO, <0.5 mol%). Some of these, when emitted from Gas solubility The maximum amount of a gas that can be dissolved active vents (Figure 57.1), react in the atmosphere or vol- in a given amount of water at 20 C; measured in g/L. canic plume to form aerosols, the most important being dgas The vapor density of a gas relative to air (density ¼ 1); measured in g/L. hydrochloric acid (HCl), hydrofluoric acid (HF), and sul- furic acid (H2SO4). 1. INTRODUCTION 2. TOXICITY OF VOLCANIC GAS SPECIES Gases are the invisible yet often continuous products of volcanic activity. Even volcanoes in a state of quiescence, It is difficult to determine accurately the contribution of not actually erupting or showing signs of unrest through gases to volcano-related deaths, since much of the data seismic activity, are able to degas continuously. Eruptions reflect deaths during eruptive periods, whereas the majority can produce lethal quantities of toxic gases, but long-term of gas-related deaths occurred during noneruptive periods. exposure to a lower dose also can pose a significant hazard. The long-term health effects of volcanic gases are poorly Although volcanic gases are only directly responsible for understood; they may be responsible for or accelerate 1e4% of volcano-related deaths, they are nevertheless epidemic diseases because of their irritant and depressing The Encyclopedia of Volcanoes. http://dx.doi.org/10.1016/B978-0-12-385938-9.00057-2 985 Copyright Ó 2015 Elsevier Inc. All rights reserved. The Encyclopedia of Volcanoes, Second Edition, 2015, 985e992 986 PART | VII Volcanic Hazards TABLE 57.1 Toxicology of Volcanic Gases and Aerosolsdcont’d Sulfur dioxide (SO2) Characteristics Colorless gas or liquid (<À10 C) with characteristic pungent odor. Perceptible odor at 0.3e1.0 ppm and easily noticeable d ¼ at 3 ppm. gas 2.26 g/L. Gas sol- ubility ¼ 10 g/L. PEL ¼ 5 ppm in air; 13 mg/m3 of air. Effects of overexposure Short-term Inflammation and irritation of the eyes and respiratory tract resulting in burning of the eyes, coughing, and difficulty FIGURE 57.1 Degassing vent of Santiago crater at Masaya volcano, in breathing. Approximately 90% Nicaragua, 2006. of inhaled SO2 is absorbed in the upper respiratory tract, where it forms sulfurous acid which then oxidizes to effects, which reduce the resistance of ocular, respiratory, form sulfuric acid. Concentrations of e and digestive systems to microbial attack. From a health 6 12 ppm cause immediate irritation of nose and throat. Exposure to >20 ppm perspective, the most important volcanic gases and aerosols causes irritation of the eyes, while concen- are CO2,SO2, Rn, H2S, HCl, HF, and H2SO4 (Table 57.1). trations of 10,000 ppm irritate moist Exposure to these has been the cause of the majority of skin within minutes. volcanic gas-related fatalities. Long-term Prolonged exposure to low concentrations may be dangerous for persons with preexisting cardiopulmonary diseases. Hydrogen sulfide (H2S) TABLE 57.1 Toxicology of Volcanic Gases and Aerosols Characteristics Colorless, flammable gas with offensive odor (rotten eggs). Characteristic Carbon dioxide (CO2) odor perceptible at 0.77 ppm and easily d ¼ Characteristics Colorless odorless gas. Irritation of eyes, noticeable at 4.6 ppm. gas 1.19 g/L. nose, and throat only at high concentra- Gas solubility ¼ 2.9 g/L. PEL (averaged d ¼ 3 tions. Vapor density relative to air ( gas) over 10 min) 20 ppm in air; 28 mg/m ¼ 1.52 g/L. Gas solubility in water at of air. 20 C ¼ 0.14 g/L. Permissible exposure limit (PEL) averaged over 8 h ¼ 5000 ppm Effects of in air; 9000 mg/m3 of air. overexposure e Effects of Short-term Inhalation of 20 150 ppm may cause eye overexposure irritation, while slightly higher concentra- tions cause irritation of upper respiratory Short-term A simple asphyxiant, symptoms appear tract. In low concentrations, exposure only when such high concentrations are may result in headache, fatigue, dizziness, reached that there is insufficient oxygen excitement, staggering gait, diarrhea, fol- to support life. Inhalation may cause rapid lowed sometimes by bronchitis and bron- breathing and increase heart rate (at chopneumonia. In small amounts the gas >7.5%), headache, sweating, dizziness, acts as depressant and as stimulant in shortness of breath, muscular weakness, larger amounts. Very large amounts result mental depression, drowsiness, and ring- in paralysis of the respiratory center and ing in the ears. Concentrations at >11% death; exposure to 1000e2000 ppm may result in unconsciousness in 1 minute or cause coma after a single breath. less. Convulsions may occur at concentra- tions of >25%. Rapid recovery occurs on Long-term Prolonged exposure to concentrations as removal from exposure. low as 50 ppm may cause pharyngitis and bronchitis, while concentrations Long-term Prolonged exposure to concentrations of >250 ppm may result in pulmonary >10% may result in unconsciousness. edema. The Encyclopedia of Volcanoes, Second Edition, 2015, 985e992 Chapter | 57 Hazards of Volcanic Gases 987 TABLE 57.1 Toxicology of Volcanic Gases and TABLE 57.1 Toxicology of Volcanic Gases and Aerosolsdcont’d Aerosolsdcont’d Radon (Rn) Effects of overexposure Characteristics Colorless, odorless, tasteless, radioactive gas, formed from the Short-term Extreme irritation and corrosion of the skin radioactive decay of uranium. and mucous membranes. Contact with the d ¼ ¼ gas 9.73 g/L. Gas solubility 51 g/L. eyes will cause deep-seated burns, and if PEL ¼ 200 the chemical is not removed immediately, Bq/m3. permanent visual impairment or blindness may result. Skin exposure produces severe Effects of burns, which are slow to heal. Subcutane- overexposure ous tissues may be affected becoming Short-term There is no information on the blanched and bloodless, which may result acute noncancerous effects of in gangrene. A severe irritant to the nose, radionuclides in humans; however, throat, and lungs, inhalation of the vapor animal studies have reported may cause ulcers of the upper respiratory e inflammation in the nasal passages tract; concentrations at 50 250 ppm are and kidney damage from acute dangerous even for brief exposures. inhalation exposure to uranium. Long-term Repeated or prolonged exposure to lower Long-term Chronic exposure by inhalation has concentrations may cause changes in the been linked to respiratory disorders, bones as well as chronic irritation of the such as lung disease and lung cancer, nose, throat, and lungs. in humans. Smokers exposed to radon Sulfuric acid (H2SO4) are at w10e20 times greater risk for lung cancer than nonsmokers. Characteristics Colorless to dark brown, oily, odorless liquid. Irritation of nose and eyes at low Hydrochloric acid (HCl) d ¼ concentrations. gas 3.4 g/L. Gas solubi- ¼ Characteristics Colorless gas or colorless fuming l lity miscible in all proportions. ¼ 3 iquid with an irritating pungent PEL 20 ppm in air, 1 mg/m of air. odor. Detectable odor by most people d ¼ Effects of between 1 and 5 ppm. gas 1.27 g/L. overexposure Gas solubility ¼ 62 g/L. PEL ¼ 5 ppm in air; 7 mg/m3 of air. Short-term Irritation of eyes, nose, and throat. Severe burns with rapid destruction of tissue and Effects of erosion of teeth may occur. Inhalation overexposure may also lead to difficulty in breathing Short-term Irritation of the mucous membranes and inflammation of upper respiratory of the eyes and respiratory tract tract. with burning, choking, and coughing. Long-term Repeated or prolonged exposure to the va- At concentrations >35 ppm, there is por may cause erosion of the teeth, chronic irritation of the throat after only irritation of the eyes, nose, throat, and short exposure. Severe breathing lungs. difficulties may occur along with skin inflammation or burns. Concentra- tions >100 ppm will result in pulmonary edema and often 3. HAZARDS TO POPULATION AND THE laryngeal spasm. ENVIRONMENT: CASE STUDIES Long-term Repeated or prolonged exposure may lead to erosion of the teeth and skin The relative degree of hazard from volcanic gases is rash.