title: Hazards from chemicals: scientific questions and conflicts of interest.
abstract: All substances are toxic when the dose is large enough. In order to regulate the use of chemicals, we need to measure the level at which toxic effects are found. Epidemiological evidence suggests that present levels of chemical use do not lead to widespread harmful contamination of the human environment. For chemicals, most of the problems of toxicity are found in the workplace, while the population at large gets most of its toxic effects from voluntary exposure to substances such as tobacco smoke and ethanol. The prevention and control of toxic effects depends on a series of steps. This begins with measurement of toxicity in model systems, such as laboratory animals, and the estimation of the likely exposure of workers or consumers. Reliable extrapolation of information gathered from animals to the diverse and biochemically differing human population depends on understanding mechanisms of toxic effects. The toxic effect and mechanisms of action of substances such as carbon tetrachloride or paracetamol have been extensively investigated, and our ability to predict toxicity or develop antidotes to poisoning has had some success, but epidemiology is still an essential part of assessment of toxic effects of new chemicals. The example of phenobarbitone shows how animal experiments may well lead to conclusions which do not apply to man. After measurement of toxicity and assessment of likely hazards in use comes the final evaluation of the use of a chemical. This depends not only on its toxicity, but also on its usefulness. The direct effects on health may be small in comparison with the indirect advantageous effects which a useful substance such as vinyl chloride may bring. The assessment of risks and benefits of new chemicals can be partly removed from a political style of discourse, but the evaluation of the relative weight to be attached to these risks and benefits is inescapably political. The scientific contribution must be to allow the debate to take place in the light of maximum clarity of information about the consequences of use of chemicals.
mesh_terms: D000082:Acetaminophen / Q000494:pharmacology; D000328:Adult; D000818:Animals; D002252:Carbon Tetrachloride Poisoning / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004785:Environmental Pollutants / Q000009:adverse effects*; D004787:Environmental Pollution; D005260:Female; D006801:Humans; D007221:Industry; D007226:Infant Mortality; D007231:Infant, Newborn; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009026:Mortality; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D012306:Risk; D012941:Social Responsibility; D006113:United Kingdom
chemical_list: D004785:Environmental Pollutants; D000082:Acetaminophen; D003577:Cytochrome P-450 Enzyme System; D010634:Phenobarbital