Studies on the bioaccumulation and microbial degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin.

While the problem of pesticidal contamination of the environment is far from being solved, considerable useful information has emerged from the research efforts made by many scientists in recent years. First, we now know by experience that the chemicals that cause environmental problems are the ones which are extremely persistent in nature, biologically active, and easily concentrated in biological systems. Compounds which lack any of the above qualifications usually do not play any significant role in pesticidal pollution no matter how acutely toxic they are. The above analysis becomes more important, when one considers other aspects of pesticidal pollution. For instance, we are concerned about only biological effects in considering pollution, with particular emphasis on the effects on nontarget organisms. In the case of polychlorinated dibenzo-pdioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the question of bioactivity is indisputable, as it is one of the most toxic compounds known to occur as a pesticidal impurity (1-3). Its chemical stability is also questionable. Thus the central question of its hazard to the environment must be stud-