ES&T
LETTERS Educational opportunities Dear Sir: The Harvard School of Public Health is seeking candidates for enrollment in its graduate programs in occupational and environmental health. People qualified for enrollment range from recent bachelor's degree recipients to mid-career professionals. Areas in which enrollees can specialize include air pollution control, occupa tional health, industrial hygiene, ra diation protection, and environmental health management. Supplementing the teaching program are extensive opportunities for research, both for M S and doctoral candidates, in the development and application of tech niques for monitoring worker and public exposures to airborne particu lates and gases, the development of mathematical models for estimating exposures in indoor and outdoor envi ronments, air and gas cleaning in cluding the control of naturally oc curring airborne radionuclides in buildings, the application of physical and chemical methods for identifying the sources of specific environmental contaminants, and the evaluation of associated risks. A range of traineeship and fellowship support is available. The deadline for applying for fall 1983 admission is March 1, 1983. Potential applicants should contact the De partment of Environmental Health Sciences, Harvard School of Public Health, 665 Huntington Ave., Boston, Mass. 02115; (617) 732-1169. Dade Moeller, chairman Dept. of Environmental Health Sciences Harvard School of Public Health Boston, Mass. 02115 Drinking water disinfectants Dear Sir: I read with interest the fea ture article on drinking water disin fectants in the October issue. (ES& T, Vol. 16, No. 10, p. 5 54A) Last year this time I was a Fulbright-Hays Se nior Lecturer in Liberia, West Africa. Before drinking the water there it had to be filtered, boiled 20 minutes, and refiltered. One of the true pleasures in return ing to the U.S. is being able to drink water from the tap.
I ask your readers to keep the water problem in perspective. The major public health problem the world faces is supplying its developing population with "safe" drinking water. Most of these people face a lifetime of chronic "runny belly." While we in the U.S. are concerned with mutagenic effects of disinfectant by-products in order to prolong our life to an excess of 70 years, the remaining three-fourths of the world is plagued by contaminated water. Let us not neglect these people with the greatest need. Robert J. Hargrove Associate Professor of Chemistry Mercer University Macon, Ga. 31207 Dear Sir: In the October 1982 ES& Τ feature article "Health effects of drinking water disinfectants and dis infectant by-products" by R. J. Bull, several facts pertinent to the evaluation of drinking water disinfectants have been omitted. Bull cites several animal studies (1, 2) in a discussion of chlorite and its role in methemoglobinema and hemolytic anemia. Bull failed to re port, however, that in a recent study human adult males were given drink ing water with various levels of chlo rine dioxide, chlorite, chlorate, chloramine and chlorine ( J , 4). Quoting from that report, "In general, the study affirmed the relative safety and toler ance of normal, healthy adult males and normal, healthy adult male G6-PD deficient individuals to daily twelve week ingestion of 500 m L of chlorine disinfectants at a concentra tion of 5 m g / L . " This report was sponsored by the U.S. E P A Health Effects Research Laboratory, project officer R. J. Bull. In a recent epidemiologic study also conducted by U.S. E P A Health Ef fects Research Laboratory (5), 198 persons were exposed for 3 months to drinking water disinfected with chlo rine dioxide. Bull does cite this report but does not mention the finding that this "study failed to identify any ad verse effects associated with a twelve week exposure to chlorine dioxide disinfected drinking water."
Finally, in Bull's discussion of the carcinogenic and mutagenic activity of a disinfected water supply, he states, "Previous work has shown that treat ing Ohio River water with either chlorine, ozone or chloramine in creased the numbers of tumors in SENCAR mice . . ." What Bull fails to mention is that in the same experi ment Ohio River water treated with chlorine dioxide and dosed to the S E N C A R mice in the same manner as the other disinfectants did not produce tumors in the test animals (6). I agree with Bull's opinion that it is ". . . too early to provide any definitive answer to the question of the relative health risks of the various drinking water disinfectants." But excluding pertinent experimental and epidemi ological data from a review article will not expedite the process of assessing the health effects of drinking water disinfectants. Marco Aieta 143-B Escondido Village Stanford, Calif.
References (1) Heffernan, W. P.; Guion, C ; Bull, R. J. Environ. Pathol. Toxicol. 1979,2, 1487. (2) Abdel-Rahman, M. S.; Couri, D.; Bull, R. J. J. Environ. Pathol. Toxicol. 1980, 3, 431. (3) Bianchine, J. R.; Lubbers, J. R.; Chauhan, S.; Miller, J.; Bull, R. J. "Study of chlorine dioxide and its metabolites in man," ΕΡΑ600/1-81-068, NTIS PB82-109356. (4) Lubbers, J. R.; Chauhan, S.; Bianchine, J. R. "Controlled clinical evaluations of chlorine dioxide, chlorite and chlorate in man," Fund. Appl. Toxicol. 1981, / , 334. (5) Michael, G. E.; Miday, R. K.; Bercz, J. P.; Miller, R. G.; Greathouse, D. G.; Kraemer, D. F.; Lucas, J. B. Arch. Environ. Health 1981,7,36,20. (6) Bull, R. J. J. Am. Water Works Assoc. 1980, 72, 245.
Author's response Dear Sir: In some respects Marco Aieta's comments concerning my ar ticle in the October issue of ES& Τ are justified. However, I would like to point out that this paper was essen tially a reprinting of the paper I pre sented at Asilomar at the 4th Confer ence on Water Chlorination. Dr. Jo seph Bianchine reported on the human studies at the same conference. Environ. Sci. Technol., Vol. 17, No. 1, 1983
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Therefore, I felt it inappropriate to present Dr. Bianchine's data in my paper. This explains the lack of refer ence to the human studies in the ES& l'article. It should be noted, however, that the conclusion quoted by Aieta does not rule out an effect in humans. The 5 m g / L dose used in the clinical study was one-tenth of that required to see effects in experimental animals. The epidemiological study quoted was conducted after C10 2 disinfection had ceased for a short period of time. Consequently, conclusions of neither study contradict animal studies if that is Aieta's concern. The major question, however, is not what CIO2 and its by products do to normal humans, but what they do to people who are very sensitive to hemolytic agents. Neither the clinical nor the epidemiological studies adequately addressed this issue. I have more difficulty with Aieta's charge concerning the SENCAR data. The data from that experiment are included in the article quoted in ES& Τ with the results of two additional studies of the same design. On balance there is nothing to indicate a consistent
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Environ. Sci. Technol., Vol. 17, No. 1, 1983
difference between the disinfectants with experiments of this type. Conse quently, to take the standard suggested by Aieta is indefensible in view of present information. These data are in press in Environmental Health Per spective (reference # 4 1 ) and will be available soon. Richard J. Bull, director Toxicology and Microbiology Division Health Effects Research Laboratory U.S. EPA Cincinnati, Ohio 45268 Crop losses and air pollution Dear Sir: Bette Hileman's recent ar ticle (ES&T, Vol. 16, No. 9, p. 495A) describing crop losses caused by air pollutants and the research under way to assess losses was excellent. I wish to comment and elaborate on some items in the article. There is increasing evidence that ozone damage to crops is widespread in the eastern half of the U.S. as well as in Southern California. Frequently ozone injury to leaves is ignored be cause it is thought to be natural leaf senescence, which is somewhat similar in appearance. With ozone injury the older leaves became chloratic, or yel low prematurely, have a wide range of leaf markings primarily on the upper leaf surface, and leaves may drop from the plant. Ozone causes destruction of chlorophyll; consequently, photosyn thesis declines. If more persons could see, as I have, at mid- and late season the dark-green, old as well as young, leaves protected against ozone-induced leaf injuries in the open-top chambers supplied with charcoal-filtered air (e.g., potato leaf, p. 498A) and the yield increases of crops such as soy beans, cotton, potatoes, tomatoes, sweet corn, snap beans, lima beans, etc., they would be more interested in the problem. The open-top chambers used in the National Crop Loss As sessment Network ( N C L A N ) permit the culture of many crops from the seedling stage to maturity with mini mal chamber effects. Interest in surface ozone (as con trasted to stratospheric) measurements and in crop losses due to ozone air pollution was stimulated about 25 years ago by the discovery that ele vated ozone levels caused injury to leaves of grapes in California and to bacco in the eastern U.S. (Richards, B. L.; Middleton, J. T.; Hewitt, W. B. Agronomy J. 1958, 50, 559; Heggestad, H. E.; Middleton, J. T. Science 1959,129, 208). At that time the pri mary concern, especially regarding tobacco, was the injury to leaves. In the past decade, we have learned that yield
reductions due to ozone in ambient air can be significant for ozone-sensitive crop species and cultivars. Sometimes this occurs with very little visible injury to leaves. Also, there may be leaf in juries without significant loss in yield of seed or fruit. A major deficiency in making re gional or national estimates of crop losses is the inadequacy of ozone monitoring data for agricultural areas. I find it difficult to believe that some countries in North Carolina appear to have higher ozone levels than other locations in the U.S. (map, page 497A, September 1981 ES&T). However, an average 7-h ozone level of 0.07-0.08 ppm, indicated for North Carolina, was found by EPA at 27 of 171 U.S. sites included in an analysis of mean 2-month values in 1975, 1976, and 1977. Twenty-one sites had 2-month average 7-h levels of ozone ranging from 0.08 to 0.11 ppm, and for Phila delphia and Los Angeles the ozone levels were higher (EPA. "Evaluation of alternative secondary ozone air quality standards"; O A Q P S 78-8, IV-A3, U.S. E.P.A.: Research Trian gle Park, N.C., 1979). Most of the sites were identified as urban centers; a few were rural. Analyses of data sets for 1979 and subsequent years and additional monitoring in rural areas, including those that may have only normal background levels of ozone, are need ed. There should be more monitoring and data analyses also at the N C L A N sites so the ozone exposure doses re ceived by the plants in the chambers, now measured and controlled with the probes in the chamber centers near the top of the plant canopy, can be better related to ozone in ambient air some distance away from the crop and the chambers and at 3 m (height of sam pling for S A R O A D monitors). N C L A N participants follow an es tablished general protocol, but each year the scientists from different dis ciplines meet to review results, set priorities, and modify plans to improve efficiency and the data base. During the year, N C L A N ' s very dedicated Research Management Committee handles many matters by conference calls. I strongly support a statement made in your article that the data generated by the program ". . . are absolutely necessary for making meaningful cost-benefit analyses »?
Howard E. Heggestad Research Plant Pathologist U.S. Department of Agriculture Agriculture Research Service Beltsville, Md. 20705
