measurement of residues has approached standardization, and prediction of residues 

 from chemical structure appears to be within reach. 



The role of DDE in causing egg shell thinning in birds was more clearly elucidated, 

 leading to an almost certain explanation for the decline in populations of certain 

 groups of birds. The banning of many uses of some "hard" insecticides and the 

 subsequent recovery of wild populations confirmed the laboratory findings. The 

 dramatic drop in DDT residues in Lake Michigan fishes provided another validation 

 that laboratory-derived data were indeed applicable to the field situation. Laboratory 

 data are much cheaper and quicker to obtain than are field data. Furthermore, they 

 can be obtained before the problem exists in the natural environment. Such data then 

 have the virtue of being predictive rather than retrospective in nature as field data, by 

 necessity, must be. This virtue is an important one as the pre-market testing 

 requirements of the Toxic Substances Control Act are promulgated. 



The demonstration by Ringer*" that mink on mink farms suffered reduced 

 reproductive capacity as a result of xenobiotic chemical residues in their food 

 provided more evidence that everything is connected to everything. More 

 importantly, several of the findings mentioned above pointed up the serious 

 consequences of persistent residue-forming chemicals widely released into the 

 environment. Just as biochemical oxygen demand (BOD) in the 1950s and 

 insecticides in the 1960s received the research spotlight, perhaps one could conclude 

 that residues of man-made chemicals in fish and wildlife constituted one main focus 

 of attention in the 1970s. Indeed, perhaps more regulatory actions and more 

 headlines have stemmed from excessive residues than from direct toxicity from the 

 ambient medium: air or water. 



The close of the decade, with the passage of the Toxic Substances Control Act and 

 the realization that the number of compounds in use was in the tens of thousands, 

 created a demand for rapid and inexpensive tests to make safety judgments on more 

 chemicals for a given amount of resources. Thus, life cycle tests lasting many months 

 or one or more years are waning and shorter toxicity tests are being developed to 

 replace them. Toxicologists perhaps saw that knowing something about nearly all 

 chemicals was more valuable for protecting the environment than knowing a lot 

 about only a few chemicals. The recent leveling or even decline in research budgets 

 and staff made this change an obvious necessity in order to stretch shrinking 

 resources. The exceedingly short time frames for decisionmaking under the Toxic 

 Substances Control Act vividly brought to our attention the need for faster tests. 



Hazard Assessment 



As environmental control progressed, environmental toxicologists recognized 

 several other principles as important to their success. For one, toxicity of a chemical 

 was not the whole story. The expected environmental concentrations at the critical 

 place and times were equally as important as toxicity in deciding what the actual 

 impact would be. As the decade has progressed, environmental chemistry and 

 toxicology have been drawn ever closer together. Both are necessary to make valid 

 decisions. Knowledge of such phenomena as environmental compartmentalization 

 (deposition in sediment or residue formation in animals), persistence, volatility and 

 degradation products is needed along with toxicity data to make judgments of effects 

 in the ecosystem. Indeed, environmental chemistry has grown to play a vital role in 

 laboratory toxicology. 



Toxicologists, recognizing the need to test more than onespecies and also the 

 resource constraints, began to question what and how many species should be tested. 

 This concern led to new terms describing new concepts such as tiered testing, triggers, 

 surrogate species and functional indicators. More and more, practical decision- 

 making needs were forcing toxicologists to select point concentrations above which 

 harm would occur and below which safety was assured (often without the hedge of a 

 safety factor). Such a job is at least exceedingly difficult when, in fact, one is faced 



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