Many chemicals found in industrial, commercial, and household environments are toxic under certain conditions. Among the most common are asbestos, benzene, vinyl chloride, acrylonitrile, and phthalates. All are important industrial materials widely distributed in various forms, and all have serious health effects. Polychlorinated biphenyls (PCBs) were important industrial chemicals until their effects were demonstrated and production was stopped. The toxic hazards of certain pollutants, particularly in the petrochemical industry, may be increased by the fact that these pollutants are themselves often contaminated by impurities.
The flow of industrial chemicals into the environment varies with the chemical. Asbestos (including natural sources) and benzene are present in varying concentrations throughout the environment. Most asbestos fibers that are released directly into the air come from mining and milling; but once an asbestos product has been manufactured, release of fibers into the environment is highest in the use of brake linings and other friction products and in the deterioration of thermal insulation and construction materials. Demolition of buildings is an important source of asbestos contamination, and asbestos is also leached into drinking water from concrete water pipes. Industrial workers and miners are usually the most affected although, as materials made with asbestos deteriorate, the general public can be exposed. Benzene, an organic compound derived from petroleum, is an intermediate in the production of plastics, dyes, nylon, food additives, detergents, drugs, and fungicides. It is also used as a gasoline additive. Vinyl chloride gas is released directly at the workplace, although small amounts are released as consumer products deteriorate and are disposed of. Phthalates, a class of intermediate synthetic organic chemicals, are in widespread and growing use as resin in the production of plastics, models, cement, paints, and finishes. Acrylonitrile is used as a resin in the production of plastic bottles, acrylic fibers and textiles. Combined with butadiene and styrene, acrylonitrile forms a polymer, ABS, widely used in appliances, automobiles, luggage, telephones and many other common industrial and household products. Vinyl chloride is a gas used in the production of plastics. PCBs, liquids previously used in ink solvents, adhesives, textile coatings, and pesticides, are now used only in electrical transformers and other closed systems, but many products containing PCBs remain in use. The major source of PCBs is through improper waste disposal, especially into bodies of water. PCBs contaminate wildlife, fish in particular. The threat to human health is through the food chain - in fish, poultry, and meat. PCBs are widely distributed in the environment very much like DDT, which PCBs resemble structurally; and, like DDT, they are highly persistent.
An estimated 70,000 to 80,000 chemicals are now produced and traded, representing some 10% of total world trade. A further 1,000 to 2,000 new chemicals enter the commercial market each year. Of a sample of 65,735 chemicals in common use in the USA in 1984, data for complete health hazard assessment was available for only 10% of pesticides ad 18% of drugs. No toxicity data was available for nearly 80% of the chemicals used in commercial products and processes. Where chemicals are discovered to have toxic properties according to the criteria of one country, they may be withdrawn from testing (or not submitted), and then manufactured only for export to countries with less stringent regulations.
WHO estimates that 75 to 80% of all cancers are triggered by environmental pollutants, foremost among them industrial chemicals. In 1980 the chemical industry in the industrialized countries of Europe and North America had a total turn-over of US$ 550 billion, employing a full six percent of the entire workforce of the OECD member countries. Inadequate chemical waste disposal remains a serious threat to the health and welfare of Europeans and North Americans.
Unlike the industrially advanced countries, most developing countries do not have toxic chemical control laws, nor the technical or institutional capability for implementing such laws. Catastrophic results have resulted from escape of toxic chemicals into crowded neighbourhoods near factories as a result of industrial accidents. During the last decade, several cases have come to light where products banned or severely restricted in the industrialized countries were sold to, or 'dumped' on, the developing countries.
Production of benzene, phthalates, acrylonitrile and vinyl chloride has increased rapidly during the past 20 years. Almost 11 billion lbs of benzene were produced in 1978, making it one of the high-volume organic compounds in domestic production. Vinyl chloride production continues to grow, along with the use of plastics in industrial and consumer products. Asbestos production, on the other hand, has not increased appreciably. PCB production in the USA has declined since 1970 as a result of self-imposed restrictions by the major manufacturer. By law, the manufacture of PCBs was prohibited after July 1979, except when specifically exempted by EPA.