LETTERS Biodegradation of organic chemicals Dear Sir: Martin Alexander’s excellent article in the February issue of ES&T (“Biodegradation of organic chemicals,” p. 106) reminds us of a fact we need to remember: One cannot extrapolate results obtained under one set of conditions to another without knowledge that no change in mechanism has occurred. Just as the toxic effects of chemicals observed at high doses do not necessarily occur proportionately at low doses, degradation rates at concentrations appropriate under conditions at sewage treatment plants do not necessarily occur in the environment at high dilution, for all the reasons he states. It is unfortunate that Alexander did not use the opportunity he had to remind your readers of two other facts that complement those he brought out. First, biological mineralization is not the only mechanism by which xenobiotics are removed from the environment. Second, the modern concepts of hazard assessment and risk management are based on the idea that concentrations of any substance below its lowest “effect” level are of little consequence. Most complex organics are susceptible to attack by a variety of agents present in the environment. 2,3,7,8TCDD photodegrades rapidly to phenoxyphenols that are biodegradable. Hydrocarbons react with atmospheric oxidants such as ozone or hydroxyl. Complex amides, such as monuron, phthalates, and other esters, hydrolyze. In many cases these compounds biodegrade faster at “high” concentrations, but it is important to recognize that competitive degradation processes will go on, even if a “threshold” for biodegradation exists. Nevertheless, if a compound is being released to the environment, either continuously or episodically, some concentration will exist. If a concentration exists, the steady advance of analytical technology ensures that sooner or later it will be detected. This fact implies that we who work in the environmental field need to recognize the difference between the mere presence of a compound and its posing a threat. The popular press often confuses the first with the second; we scientists must not. Centuries of experi-
ence with drugs and poisons has taught us that small enough doses of the most powerful poisons cause no harm. That is, if we know the dose or ambient concentration below which no effects occur, and the true dose or concentration is well below that level, we need have no concerns. Thus, even if the biodegradation of a compound becomes very slow at very low concentrations, degradation by other processes goes on. This means that slower biodegradation need not imply that release of that compound to the environment poses any threat to humans or to the other species with which we share our environment.
stream (ES&T, January 1985, Currents, p. 6). The note credits Enviro-Health Systems of New Orleans, La., which was established in 1984, with the development of the chlorinated pesticide screening test. Actually, the screening test approach for chlorinated pesticides was conceived in 1981 by personnel at our laboratory, the Center for Bio-Organic Studies, and was subsequently developed (adapted from the literature to capillary GC) as part of a research program at the center from January 1982 through November 1983. Preliminary results of our work were published in the fall 1983 issue of Clinical Ecology.
James D. Wilson
Ildefonso R. DeLeon Acting Director Center for Bio-Organic Studies University of New Orleans New Orleans, La. 70148
St. Louis, Mo.
Environmental fellowship program Dear Sir: The German Marshall Fund of the U.S. and the Institute for European Environmental Policy (Bonn, West Germany) are renewing the Environmental Fellowship Progam for U.S. professionals, now in its sixth year. (See ES&T, April 1985, Currents, p. 296.) During 1985-86, up to five fellowships will be awarded. These short-term fellowships are for those who are interested in gaining firsthand knowledge of selected environmental policies of European countries. Fellows will spend up to two months in two or three European countries, under the guidance of the institute’s staff in Bonn, London, and Paris. They will examine specific issues of environmental policy making that are of direct relevance to their work in the U.S. Applicants must have a good working knowledge of another language (French, German, Italian, or Spanish) in addition to English. During the past five years, 25 U.S. fellows have participated in the program. Deadline for applications is June 14. For details and application procedures call Marianne Ginsburg, 202-745-3590. Marianne Lais Ginsburg The German Marshall Fund of the United States 11 Dupont Circle, N. W. Washington, D.C. 20036
Pesticide residues in humans Dear Sir: I noted with great interest the item on pesticide residues in the blood-
T=SHIRTS Your DNA has its
-so
way with this ingene-ious T-shirt. Blue pocket and red print on beige 50% cottoni50Y0 poly machine washable blend. Small (34), Medium (36-38), Large (40-42), Extra Large (44). Write for quantity discounts.
American Chemical Soclety, Education Div. 1155 Sixteenth Street, NW (202) 872-4588 Washington, OC 20036, USA Please send “ i have Designer Genes ’ T-shirts as follows
~..-S_____M--.L~-XL I understand the price is $8 50 each plus $1.95 per order, U.S.A. ($3.70 foreign) for shipping and handling c1 Check enclosed
a Visa No.
Exp. Date
__3 Mastercard No.
Interbank Code
E X Date ~
Name Address
___ city
State
zip
Environ. Sci. Technol., Vol. 19, No. 5,1985 379
