In order to make a sound decision, it is necessary to know whether the 

 environmental concentration is indeed below the "no adverse effects" concen- 

 tration. In Figure la the environmental concentration is well below the no 

 adverse effects concentration and a modest amount of "testing," corresponding 

 to the point P, shows that there is no overlap in uncertainty. At a reason- 

 able risk, therefore, the chemical can be produced and used. 



In the next case (Figure lb) the two concentrations have a similar rela- 

 tionship: the environmental concentration is lower than the "no adverse bio- 

 logical effects" concentration. However, because the two concentrations are 

 so close, one must continue to Tier 3 testing before making the same decision 

 as in Figure la and with the same degree of confidence. This method, coupled 

 with the priority matrix, is one way to determine how many tests are necessary 

 to make a reasonable judgment as to when one can use a chemical with relatively 

 low risk. In other words, this approach helps to determine how broad the in- 

 formation base needs to be. 



The 1976 Toxic Substances Control Act states that evidence shall be pro- 

 vided for all new chemicals regarding their hazard to human health and envi- 

 ronment. This includes the extraction, manufacture, transportation, and dis- 

 posal of such chemicals. The ruling also applies to existing chemicals that 

 are being used for a new purpose. In Figure lc continued testing shows that 

 the environmental level is above the "no adverse effects" level with the same 

 degree of confidence. In this case, the Administrator of the Environmental 

 Protection Agency would be required to either ban or restrict the use of the 

 chemical. A cost-benefit analysis is then warranted to ascertain whether the 

 benefits to society are greater than the environmental damage associated with 

 the use of the chemical. 



A strategy exists for proceeding through the three tiers of protocols 

 It is derived from a study for the Army Medical Command on hazard assessment 

 related to effluents from Army ammunition plants (Cairns and Dickson 1978). 

 The philosophy underlying protocols is discussed in the book, Estimating the 

 Hazard of Chemical Substances to Aquatic Life (Cairns et al. 1978) . Another 

 book is in press (Dickson et al.) that incorporates many of the protocols used 

 by industrial societies worldwide, including Japan and Germany. Although the 

 details are different, the strategy used in each country is the same. It is 

 interesting to note that each country developed its protocols without much 

 awareness of the other countries' efforts. 



The basic protocol strategy consists of concurrent laboratory and field 

 studies (Figures 2 and 3). Beginning with a broad trophic-level base of or- 

 ganisms such as algae, invertebrates, and fish, it identifies the most sen- 

 sitive of these trophic levels with the inexpensive tests. The increasingly 

 expensive, difficult, and sophisticated tests are conducted only on the most 

 sensitive component in the trophic level system. Decisions are alternated 

 with data-gathering, using an increasing focus on what is, on the basis of 

 the evidence collected, the most sensitive link in the chain. 



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