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GUEST EDITORIAL
Controlling toxic substances: setting research priorities In the early 1950's, it was discovered that h!,drocarbons and nitrogen oxides react i n the atmosphere in the presence of sunlight t o form netv, more noxious s u bs t ;I nces-- phot oc h e in ica 1 s i n og . I d e n t i fi ca t ion o I rhe sources of the smog precursors. l a r g e l ~automobilc ~ emissions and power-plant stack gases, led to govern men t reg u 1a t i on of two major i n d us t r i es -a u tomobile manufacturing and electric power generation. The technological and economic consequences have been profound. Now we are moving toward the regulation of another major industry: the chemical industry manuI'actures substances used in products runging from jynthctic fibers and pesticides to menibrancs for artificial lungs and kidneys. Industry sales exceed S IO0 billion per year with over 30 000 chemicals on the market and perhaps a thousand new ones introduced each year. Inevitably. given the size and complexity of the industry. chemicals have escaped to the environment through air and uatcr routes and caused harmful efI'ccts on human health or the ecolog). scientific all!^. the problem is in some w \ s much more complex t h a n those which have been handled i n the past. One of the main problems is the variabilit! in the nature of emissions from the chemical industry bec;iuse the sources are of so inan)' d Typical chemical industry emissions ;ire not ;is nell defined as, say, automobilc exhaust or stack gases I'rom coal-fired power plants. This complicates efforts to define surrogates or indicators for classes of toxic substances. Another difficulty is that thc concentrations of the chemical species of concern are often very low and hard to detect with available inslruiiicntation. Finally the time scale over which biological and ccological effects itre produced may be long, comparcd w i t h the time scale for conventional pollutants. Although control of these substances is essential, heavy-handed regulation would be :I mistake. Red tape and loss of proprietary position will discourage
innovation by industry. The result will be the loss to society of useful new products and processes. Government and industry are now grappling with the development of procedures for dealing w i t h these problems. This is a critical time because precedents ;ire being set. One might say. "Identify all potentially to x i c s u bs t :t n ccs p r cse n t i n i n d us t r i ;t I e in i ss i o n s a nd require that industry remove them. Do the same for ne\% technologies before they go into production." Indccd, both industry and the EPA are relying heavily on toxicological studies and other biological tests for 5 c r c e n i n g t he ni a n y c h e in i c;t I co in po u n d s i n vo I v ed . It would be a mistake to make this the main focus of the toxic substances control program. I n many c;tses, neither the level of human exposure, nor the relative importance of the sources is known. For ex:tinple. urban and industrial regions such its New .Icrsey and the Houston ;\rea contain niany different sources of chemical emissions. Met hods have been developed for the resolution of complex a i r quality/ cmission source relationships for certain classes of pollutants. High priority should be given to extending these methods to potentially toxic organic chemicals. Thc results of such studies should be used in setting priorities for emission control based on source contributions to human exposure. They should itlso pro\.idc guidance for biological screening tests :it concc n t rii t i on s cor res pond i ng to rca I i s t i c eva 1 u a t ion s of human exposure. Let's put numbers on human exposure and source contributions.
Dr. S. K. Friedlander I S Professor of Engineering and Applied Science and ViceChairman. Chemical Eneineerine at the Unicersity of California.1 0 s Angdes. Volume 13, Number 3, March 1979
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