The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals 124. Thermal Degradation Products of Polyethylene, Polypropylene, Polystyrene, Polyvinylchloride and Polytetrafluoroethylene in the Processing of Plastics

摘要

Plastics are subjected to elevated temperatures in the processing. This gives rise to complex mixtures of substances. The quality and quantity of these depends, e.g. on the type of the polymer, additives, and the degradation temperature. This criteria document covers the occupational health effects caused by the thermal degradation products from five plastics at processing temperatures. The industrial hygienic measurements have shown that the concentrations of individual compounds in normal processing are much lower than their Nordic occupational exposure limit values. The dose-response data is insufficient and so there are no scientific foundations for occupational exposure limits. Polyethylene and polypropylene. The major degradation products under relevant conditions are formaldehyde, formic acid, acetaldehyde, and acetic acid and other aldehydes and acids. Aerosols are formed in significant amounts. Alkoxy radicals have also been detected. Respiratory irritation found in animal studies suggest that this might be used as a critical effect. Observed effects in man are mainly case reports of bronchoconstriction. Polystyrene. Styrene is the most significant degradation product. Other notable products are aerosols, carbonyl compounds and formic and acetic acid. The only reported adverse effect in humans in the processing industry has been increased risk of abortions but no quantitative exposure assessment is available. Polyvinylchloride. Hydrogen chloride is the main product from polyvinylchloride. Other products are emitted at much higher temperatures than in processing. The most abundant emissions usually originate from additives (like phthalates). Aerosols are also emitted. Workers have complained of irritation in eyes and respiratory tract. In these cases the degradation temperatures have been, however, unusually high. The best-known adverse effect is the meat wrapper's asthma but the causative agent is not known. The fumes can also affect adversely lung functions. Polytetrafluoroethylene. The major gaseous products are hydrogen fluoride, carbonyl fluoride and fluorinated hydrocarbons. Ultrafine particles have been the cause of toxic pulmonary and lethal effects in experimental animals. Large doses of fumes cause pulmonary inflammation, haemorrhage, oedema and even death in experimental animals. Similar effects have occurred in humans who have accidentally inhaled fumes from degradation at exceptionally high temperatures. The best-known adverse effect is polymer fume fever with flu-like symptoms. Smoking of contaminated tobacco products has been the cause in the majority of cases.