Behavioral Toxicology and Environmental Health Science Opportunity and Challenge for Psychology

Behavioral Toxicology and Environmental Health Science Opportunity and Challenge for Psychology Bernard Weiss University of Rochester School of Medicine and Dentistry ABSTRACT: Behavioral toxicology is now established nervous system mechanisms, produce distinct be- as a component of the environmental health sciences. havioral reactions. For example, the main oxidant in Its rise paralleled recognition that the adverse health photochemical smog, ozone, is a deep lung irritant impact of environmental chemicals should be gauged eliciting subjective discomfort. by how people feel and function, not solely by death This unique role for psychology grows out of a or overt damage. Its compass extends across the total new perspective by the environmental health sciences, spectrum of environmental chemicals, including heavy particularly environmental toxicology, and by public metals, solvents, fuels, pesticides, air pollutants, and health leaders. Toxicology, the science of poisons, used even food additives. Psychology can help resolve many to be a discipline ruled by the clear criteria of death critical issues in environmental health science. and tissue pathology. The new issues that emerged from our delayed recognition of environmental haz- ards, however, stimulated new questions about adverse Odious waterways and corrosive smog are such tan- effects on health. Were death or tissue lesions the only gible evidence of pollution that they evoke tangible feasible end points? What about disturbances of func- remedies. But eliminating blatant pollution is no more tion? Isn't it important to discover how people feel than a first step in managing the environment and and perform or to intervene when "behavioral changes protecting human health. Some of the most toxic dangerous to a patient and others can occur before contaminants are also the most elusive. How can we the individual realizes that he or she is poisoned" assess the impact of chemicals that, in passing through (Michael, 1982)? Once we were alerted to these ques- the environment, may be transformed into other sub- tions about function, it was a natural step to turn to stances, may be dispersed by atmospheric processes, the discipline whose business it had been for over a may enter the food chain in unpredictable guises, or century to provide scientific answers to questions of may trigger biological reactions whose consequences this type. remain dormant for decades? To multiply this am- Behavioral toxicology is so young that its formal biguity, how do we evaluate toxic processes expressed debut in the United States did not occur until June other than as overt disease or death? Especially, how 1972, shortly after the winter snows had melted in do we detect an insidious degradation of function, Rochester (Weiss & Laties, 1975). Like many new especially if it unfolds gradually over years of toxic disciplines, it coalesced from fragments of old ones: exposure or after a latency of half a lifetime? toxicology and its emphasis on pathology, behavioral The nascent discipline of behavioral toxicology pharmacology and its parallel inquiries about drug arose as one response to such questions. Behavioral effects, industrial hygiene and its recognition of func- measures were seen to fulfill unique roles. One derives tional indexes as the basis for many standards of al- from the realization that many substances act pri- lowable exposure to workplace chemicals. It is also marily on the nervous system. They include heavy indebted to I. P. Pavlov, because his stature in Soviet metals such as mercury, lead, and manganese; organic science helped to elevate CNS function to a sovereign solvents such as carbon disulfide and toluene; pes- place in USSR hazard assessment (Glass, 1975). ticides such as the organophosphates; air pollutants Behavior also was seen to have special virtues such as carbon monoxide. A second reason is more as a criterion of adverse effects. First, it is a nonde- subtle; it derives from the observation that many poi- structive assay: Its subjects' livers need not be fed sonings, before they bloom into overt clinical signs, into a blender to quantify damage. Also, it is an assay may be heralded by vague, subjective, nonspecific system (Weiss, 1978b) reflecting an Organism's total psychological complaints. Finally, there are substances functional capacity, not simply one component of it. whose actions, although not mediated directly through Such attractive attributes come at a price, however. 1174 November 1983 • American Psychologist Copyright 1983 by the American Psychological Association, Inc. Behavior's global nature also may allow compensatory quantifying nonspecific neuropsychological features mechanisms to thwart the early detection of an ir- of toxicity, especially early in the course of poisoning reversible pathological process. Behavioral assays are when many of them are likely to be subjective. They expensive, especially when compared, for example, also demonstrate how psychological approaches such to in vitro tests of mutagenesis. Behavioral methods as psychophysics could help detect and trace subtle also offer a bewildering spectrum of choice, which is sensory impairment. A discussion of pesticides shows an advantage in pursuing a science of behavior, but how monitoring adverse effects by psychological mea- an aggravating source of indecision for a chemical sures may yield more information than monitoring manufacturer or regulatory agency forced to define them by blood chemistry. Air pollutants are used to hazard. Perhaps most troublesome of all, how are exemplify a class of contaminants whose effects may functional measures to be evaluated? What actions not lie directly within the nervous system; in some are implied by a finding that the current workplace instances, these effects are best revealed by behavioral exposure standard for a volatile organic solvent methods. Finally, in a discussion of food additives," I lengthens reaction time by 10%? Or by a report that try to show how the neglect of behavior in safety prenatal treatment with high doses of a common pes- testing has provided misleading estimates of safety ticide elevates locomotor activity in two-month-old margins. rats? These are not idle questions or academic ex- ercises; standards and regulations may be built on Metals them. The Toxic Substances Control Act (TSCA) of Metals are so ubiquitous that many of them came to 1976 specifies behavior as one of the criteria for judg- play essential roles in the evolution of living systems ing the safety of new chemicals. Unease about the (Weiss, 1978a). Other metals, perhaps because of their impairment of psychological development by lead geological distribution, remained outside the orbit of helped to diminish its role as a fuel additive. The living processes. But all metals, even the essential carbon monoxide standard prescribed by the Envi- ones, can be toxic, and the margin between essential ronmental Protection Agency (EPA) is based partly and hazardous levels may be surprisingly narrow. on behavioral data. These issues and questions become Manganese and vanadium are both essential elements, clearer in the context of specific substances. I've cho- yet they have been implicated in syndromes ranging sen, from many possibilities, a set of agents meant from movement disorders resembling parkinsonism to illustrate the diversity of settings, issues, and con- to manic-depressive psychosis. Excessive exposure to taminants that entail psychological questions. metals can damage many different organ systems and I will begin by discussing metals, because they biological processes and has been implicated in a re- are the most ancient pollutants released by human markable range of adverse signs and symptoms in- activities. Metallic mercury demonstrates the im- volving the central nervous system (CNS) and be- portance of quantitative measures of motor function havior (Figure 1). in assessing subclinical impairment, as well as the lack of sound psychophysiological data about the total Mercury syndrome of mercury poisoning. Methylmercury, a Among the best documented entries in Figure 1 are highly toxic organic compound of mercury, illustrates those associated with mercury. This slippery, silvery the discipline and problems of behavioral teratology, metal, liquid at room temperature, is one of the metals that is, the consequences of prenatal toxic exposures. exploited by humans since antiquity. Its toxicity has Another metal, lead, shows how difficult it still is, been recognized almost as long (Maurissen, 1981). even after an immense outpouring of research, to The cardinal sign of mercury-vapor poisoning is disentangle toxic behavioral consequences from other tremor, which begins to develop around the eyelids environmental variables and to relate them to ap- and eventually invades the limbs, especially the hands. propriate biological measures of exposure. Organic Inorganic mercury compounds at one time were used solvents illustrate even more graphically the issue of to prepare animal hairs for felt hats. These processes released mercury vapor into the factory atmosphere, Parts of this article are based on invited addresses presented during exposing workers to concentrations above the safety the past 10 years to the American, Eastern, and Midwestern Psy- limits prevailing at the time. Since Danbury, Con- chological Associations. Its preparation was supported in part by Grants ES-26676, ES-01247, and ES-01248 from NIEHS; MH- necticut, was the center of the industry, the mercury-

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