1 and you might say categorized into several, I think there were eight or 



2 more generic drilling muds. 



3 Again, at that time I did this slide there had been 60 bioassays 



4 reported for these. In this case, the toxicity is generally lower, 94 



5 percent or practically non-toxic or completely non-toxic. 



6 So, again, laboratory data seem to indicate that drilling muds for 



7 the most part are not a serious toxicology problem. There can be other 



8 problems in the marine environment. 



9 In addition, a large number of studies, mostly in academia, have 



10 been performed on sublethal and chronic effects of drilling fluids. 



11 Generally the concentrations causing sublethal responses are in the 



12 range of 1 to 160,000 ppm during exposure times lasting from 5 minutes 



13 to 100 days or longer. 



14 A variety of responses, alterations in behavior, especially in 



15 lobsters and so forth, embryo-larval developmental changes, growth 



16 changes, changes in metabolism or long-term survival have been recorded. 



17 Also, several people have layered drilling muds on the bottom of 



18 aquaria and then introduced animals and observed the effect. You get 



19 some behavioral responses, some changes in the recruitment of larvae to 



20 the benthos, but generally at fairly high concentrations if you think of 



21 a layer up to several millimeters thick laying on the bottom of 



22 unfractionated drilling mud. 



23 As a generalization, these chronic effects and sublethal effects 



24 are generated at concentrations anywhere from just barely lower than 



25 those that are acutely toxic to maybe 100 times lower. 



26 So, using a very conservative so-called application factor in the 



27 business of 100 fold, in other words a 100-fold dilution of the acutely 



28 toxic concentration, we can estimate how long and for how far around a 



29 drilling platform drilling muds might remain toxic, 



30 Basically, if we have a criterion value of 10 ppm that we don't 



31 want that concentration to be exceeded in the environment, then that 



32 would protect virtually the 100 percent of the animals out there. We 



33 can see that we require a 10^ dilution of that effluent. 



90 



