SAFE USE OF CHEMICALS: A Practical Guide - Chapter 7

7 Air Pollutants and Toxic Gases 7.1 INTRODUCTION Air pollutants and industrial gases cause adverse health effects in industrial workers and the general public, depending upon the manner of exposure and the concentra-tion of the candidate or mixture of pollutants. Air pollutants are toxic and hazardous to human health. It is important to know the differences between toxicity and hazard. In fact, toxicity and hazard are not synonymous terms. The word toxicity identifies the capacity of a chemical substance to cause injury or harm to a living organism, while the word hazard identifies the possibility that exposure to a chemical substance will cause an injury to the living organism when a specific quantity or concentration is used under a certain condition. Further, the characterization of a hazard takes tox-icity into account, along with several other factors, to arrive at risk determination. 7.2 SOURCES OF POLLUTANTS AND HEALTH EFFECTS Combustion of fuels produces and releases pollutants such as hydrocarbons, car-bon monoxide, oxides of nitrogen, particulate matter, sulfur dioxide, and greenhouse gases such as carbon dioxide and nitrous oxide. Air pollutants are also released by some household products—for instance, paints, paint strippers, solvents, wood pre-servatives, aerosol sprays, cleansers and disinfectants, moth repellents, stored fuels, and automotive products. Air pollutants cause mild to severe health effects in the exposed individual and involve sensitive organ systems. These include the eyes, nose, and throat; irritation, headaches, loss of coordination, nausea, and damage to liver, kidney, and central nervous system (CNS) can occur. Some organic pollutants cause cancer in animals, while some are suspected of causing cancer in humans. The signs and symptoms of poisoning caused by the volatile organic chemicals include conjunctival irrita-tion, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, and dizziness. As reported by the World Health Organization, indoor and outdoor air pollution caused very large-scale deaths in different countries of the world during 2002 (Table 7.1). 7.2.1 AIR POLLUTANTS There are many air pollutants, and the composition and level depend on several fac-tors. Air pollutants cause a range of adverse health and environmental effects. These pollutants include ammonia, carbon dioxide, carbon disulfide, carbon monoxide, chlorine, cyanide and cyanide compounds, cyanogen, diborane, fluorine and flourine 139 © 2009 by Taylor & Francis Group, LLC 140 Safe Use of Chemicals: A Practical Guide TABLE 7.1 Global Air Pollution and Human Mortality Country China India Japan Mexico Nigeria Pakistan Philippines Vietnam United States Global mortality Indoor Air Pollution 407,100 — 2,400 79,000 70,700 6,900 10,600 — 1,497,000 OutdoorAir Pollution 275,600a 120,600 23,800 7,200 14,700 28,700 3,900 6,300 41,200 865,000 a Figures indicate number of deaths during 2002. Source: Dikshith, T. S. S. and Diwan, P. V., 2003. Industrial Guide to Chemical and Drug Safety. Hoboken, NJ: John Wiley & Sons, Inc. compounds, formaldehyde, hydrogen bromide, hydrogen chloride, hydrogen sulfide, methyl bromide, methyl chloride, nickel carbonyl, nitrogen oxides, nitric oxide, nitrogen dioxide, ozone, phosgene, phosphine, sulfur dioxide, vinyl chloride, and volatile organic compounds (VOCs). The air pollutants also include high global-warming-potential gases—perfluoro-carbons, sulfur hexafluoride, hydrofluorocarbons, nitrogen trifluoride, hydrofluoro-ethers, and ozone-depleting substances. Sources of air pollution also emit quantities of other substances, which are often referred to collectively as toxic or “hazardous” air pollutants (HAPs). These pollutants can have more serious health impacts than some of the general pollutants, depending on the level of exposure. In many cases, toxic pollutants constitute a small fraction of the total hydrocarbons and or particu-late matter emissions.1 The following pages discuss in brief a few of the selected air pollutants and toxic gases and the health disorders they cause in humans. Ammonia (CAS no. 7664-41-7) Molecular formula: NH3 Synonyms and trade names: ammonia gas, ammonia, anhydrous, Nitro-Sil, liquid ammonia Use and exposure: Ammonia is a colorless gas with a sharp, penetrating, and irritating odor. It is very soluble in water and is also soluble in ethanol, diethyl ether, other organic solvents, and mineral acids. It is incompatible with oxidizing agents like perchlorates, chlorates, hydrogen peroxide, chro-mic trioxide, nitrogen oxides, and nitric acid, and with heavy metals and their salts. The primary use of ammonia gas is in the fertilizer industry, as a direct-application fertilizer and as a building block for the manufacture of nitrogen fertilizers, such as urea, ammonium nitrate, ammonium sulfate, © 2009 by Taylor & Francis Group, LLC Air Pollutants and Toxic Gases 141 and ammonium phosphate, and nitrogen fertilizer solutions. It is also used in production of nitric acid and in the fibers and plastics industries for the production of caprolactam and acrylonitrile.2,3 Toxicity and health effects: Ammonia gas is a severe respiratory tract irritant. High levels of airborne ammonia gas dissolve in moisture on the skin, form-ing corrosive ammonium hydroxide. Ammonia does not accumulate in the body. Exposure to high levels of ammonia causes irritation to the skin, eyes, throat, and lungs, as well as coughing and burns. Direct exposure to liquid ammonia causes frostbite, corrosive burns, and permanent scarring among industrial workers. Symptoms of poisoning include mild frostbite, numb-ness, prickling and itching in the affected area, a burning sensation, and stiffness of the affected area. In severe cases, the skin color turns to waxy white or yellow, blisters, and tissue death and gangrene follow. Corrosive burns of the skin have resulted from direct contact with a jet of liquefied ammonia. Direct contact with the liquefied ammonia gas causes corrosive injury to the eye, permanent eye damage, or blindness.2,3 Ammonia gas and cancer: There are no reports indicating that ammonia gas causes cancer in animals and humans. The Department of Health and Human Services (DHHS), the U.S. Environmental Protection Agency (EPA), and the International Agency for Research on Cancer (IARC) have not classified ammonia for carcinogenicity.2 Exposure limits: The Occupational Safety and Health Administration (OSHA) has set 50 ppm as the permissible exposure limit (PEL) for an 8-hour work period (time weight average [TWA]), and a short-term exposure limit (STEL; 15 minutes) as 35 ppm. OSHA and the National Institute of Occupational Safety and Health (NIOSH) have set a limit of 500 ppm as immediately dangerous to life and health.2 Precautions: Ammonia gas is very toxic and poses an explosion hazard, par-ticularly in improper storage conditions. Unprotected industrial workers should avoid all contact with ammonia gas and use of contaminated equip-ment. Ammonia gas should be stored in a cool, dry, well-ventilated area, out of direct sunlight, away from heat and ignition sources, and away from flammable material. Always use chemical safety goggles, a face shield for skin protection, chemical protective gloves, coveralls, boots, and/or other chemical protective clothing. Carbon disulfide (CAS no. 75-15-0) Molecular formula: CS2 Synonym: carbon bisulfide Use and exposure: Pure carbon disulfide is a colorless liquid with a sweet odor similar to that of chloroform, while impure carbon disulfide is a yellow-ish liquid with an unpleasant odor like that of rotting radishes. Exposure to carbon disulfide occurs in industrial workplaces. Industries associated with coal gasification plants release carbon disulfide, carbonyl sulfide, and hydrogen sulfide. Carbon disulfide is used in large quantities as an indus-trial chemical for the production of viscose rayon fibers. In fact, the major © 2009 by Taylor & Francis Group, LLC 142 Safe Use of Chemicals: A Practical Guide source of environmental indoor and outdoor pollution by carbon disulfide is caused by emission released into the air from viscose plants.4–6 Toxicity and health effects: Laboratory animals exposed to carbon disulfide experienced deleterious health effects—for instance, developmental effects, skeletal and visceral malformations, embryotoxicity, and functional and behavioral disturbances. Studies of animals exposed to carbon disulfide indicate destruction of the myelin sheath and axonal changes in both cen-tral and peripheral neurons along with changes in the cortex, basal ganglia, thalamus, brain stem, and spinal cord. Neuropathy and myelopathy were studied extensively in rats and rabbits. In the muscle fibers, atrophy of the denervation type occurred secondary to the polyneuropathy. Studies have also shown that carbon disulfide causes vascular changes in various organs of animals as well as myocardial lesions.4–6 Industrial workers exposed to carbon disulfide showed symptoms of irritability, anger, mood changes, manic delirium and hallucinations, paranoic ideas, loss of appetite, gastro-intestinal disturbances, and reproductive disorders.4–6 The slowing down of nerve conduction velocity in the sciatic nerves preceded clinical symptoms. Studies have indicated that carbon disulfide can affect the normal functions of the brain, liver, and heart. Workers exposed to high concentrations of carbon disulfide have suffered with skin burns when the chemical acciden-tally touched them (Table 7.2).5a Carbon disulfide and cancer: The U.S. EPA and IARC have not classified car-bon disulfide as a human carcinogen.4,5 TABLE 7.2 Symptoms of Carbon Disulfide Poisoning Concentration (mg/m3) 500–2500 450–1000 200–500 60–175 31–137 29–118 29–118 40–80 22–44 30–50 30 20–25 10 Exposure Period (years) 0.5 <0.5 1–9 5 10 15 10 2 >10 >10 3 <5 10–15 Symptoms and Signs Polyneuritis, myopathy, acute psychosis Polyneuritis, encephalopathy Increased ophthalmic pressure Eye burning, abnormal papillary light reactions Psychomotor and psychological disturbances Polyneuropathy, abnormal EEG, conduction velocity slowed, psychological changes Increase in coronary mortality, angina pectoris, slightly higher systolic and diastolic blood pressure Asthenospermia, hypospermia, teratospermia Arteriosclerotic changes and hypertension Decreased immunological reactions Increase in spontaneous abortions and premature births Functional disturbances of the CNS Sensory polyneuritis, increased pain threshold Source: Dikshith and Diwan, 2003.5a © 2009 by Taylor & Francis Group, LLC Air Pollutants and Toxic Gases 143 Exposure limits: OSHA has set a limit of 20 ppm of carbon disulfide for an 8-hour workday (TWA), while the NIOSH has set a limit of 1 ppm in work-room air.4,5 Carbon monoxide (CAS no. 630-08-0) Molecular formula: CO Synonyms and trade names: carbonic oxide, flue gas, CO, carbon oxide Use and exposure: Carbon monoxide is a colorless, odorless, tasteless gas that is extremely hazardous. It can be formed from incomplete burning of gaso-line, wood, kerosene, or other fuels. Carbon monoxide is also found in ciga-rette smoke and vehicle exhaust. In homes, carbon monoxide can build up from a poorly vented or malfunctioning heater, furnace, range, or any appli-ance that runs on natural gas or oil. Presence of carbon monoxide is very common inside and outside the workplace. It can be found around heat-ers, in improper use of gas- or kerosene-fired heaters or gas-fired central heating equipment combined with improper venting or poorly functioning chimney due to blocked heating flues, improper flue vent connectors, or hood installation, inadequate combustion air, from car exhaust, and gas-fired water heaters. –9 Toxicity and health effects: Carbon monoxide is a highly toxic gas that is often called a chemical asphyxiant. When inhaled, it combines with hemoglobin more readily than does oxygen, displacing oxygen from hemoglobin and thereby interfering with oxygen transport by the blood. The early symp-toms of CO poisoning include headaches, nausea, and fatigue, which are often mistaken for the flu because CO is not detected in a home. Prolonged exposure to CO causes deleterious health effects, brain damage, and even-tually death. The symptoms of CO poisoning include but are not restricted to drowsiness, nausea, tiredness, vomiting, headaches, dizziness, visual changes, abdominal pain, chest pains, memory and walking problems, brain damage, and, in severe cases, death. Exposure to high concentrations of CO causes severe headache, weakness, dizziness, irregular heartbeat, seizures, coma, respiratory failure, and unconsciousness. –11a Carbon mon-oxide poisoning can happen to anyone, anytime, almost anywhere. Depend-ing upon the period of exposure and concentration of CO, poisoning may be severe, moderate, or mild: r Extreme exposure causes confusion, drowsiness, rapid breathing or pulse rate, vision problems, chest pain, convulsions, seizures, loss of consciousness, cardiorespiratory failure, and death. r Moderate exposure causes severe throbbing headache, drowsiness, con-fusion, vomiting, and fast heart rate. r Mild exposure causes slight headache, nausea, and fatigue. The toxicity of CO results from its very tight binding to hemoglobin, the species that carries oxygen from the lungs to bodily tissues. For hemo-globin to work, it cannot bind oxygen very tightly (otherwise, it could not release it at its destination). Unfortunately, CO binds to hemoglobin 200 times more tightly than oxygen. Carboxyhemoglobin (the molecule © 2009 by Taylor & Francis Group, LLC ... - tailieumienphi.vn