LETTERS Pollutants and human reproduction Dear Sir: In reference to the article “The effect of environmental pollutants on human reproduction, including birth defects,” (ES&T , June 1981, p. 626), we find portions of the paper relative to mercury to be incorrect and grossly misleading in several respects. In Table 1, mercury is listed as one of the teratogenic metals. This writer checked one of the references associated with this listing and found that there was no mention in the reference regarding teratogenicity of metallic mercury; rather, the reference discussed methyl mercury. Based on the fetal effects for mercury listed in Table 1, we suspect that most of the references cited refer to alkyl mercury compounds and not to elemental mercury. In the last paragraph, middle column of p. 635, the authors state, “An effect of mercury and methyl mercury in decreasing male fertility is well known (37).” Ref. 37 is given as Doull, J.; Klaassen, C.; Amdur, M. “Toxicology,” 2nd ed.; MacMillan Publishing Co., Inc.: New York, 1980, p. 96. Neither mercury nor methyl mercury is mentioned on p. 96 of the reference. In fact, the authors of this textbook do a good job in emphasizing the differences in the toxicology of mercury and alkyl mercury compounds. We find no mention at all of the “well-known” effect of either mercury or methyl mercury on male fertility in any of the text on mercury in this reference. At the top of p. 635 in heavy type, set apart from the main text, is the statement, “No other compound has been involved in more poisoning incidents or claimed more victims than mercury. At Minamata, Japan, 700 cases of human poisoning were recorded with a 38% mortality rate. . . . The lack of maternal symptoms attests to the ease with which methyl mercury crosses the human placenta.” The first statement is false since mercury obviously is not a compound. And the fact of the matter is that the Minamata incident resulted from direct discharge of methyl mercury-not metallic mercury-from an industrial source. Moreover, there is little doubt that 1112
Environmental Science & Technology
carbon compounds have caused more poisoning incidents and have claimed more victims than have mercury compounds. However well-meaning the objective of this publication, your failure to properly distinguish the very different toxicity of mercury and alkyl mercury compounds results in a real disservice to the science. Edmund J. Laubusch Chlorine Institute, Inc. New York, N.Y. 10173
Author’s response Dear Sir: The letter by Mr. Laubusch points out some errors in our list of references and some ambiguous wording (in the section of our article dealing with mercury-related teratogenesis) that has apparently led to some confusion. Underlying all the points in Mr. Laubusch’s letter is a disbelief that metallic mercury or inorganic mercury compounds can be associated with teratogenic effects, abortion, or infertility. Unfortunately, Mr. Laubusch interpreted the title of Table 1 in a narrow sense. Perhaps, instead of “Teratogenic metals,” we should have used the caption “Teratogenic effects associated with metal-containing compounds.” However we, as well as the referee, thought this was obvious in the table as well as in the text (p. 634, paragraph 1). Although Mr. Laubusch read only one of the listed references in Table 1, I would like to point out that inorganic forms of mercury have been implicated in animal systems with abortions (Ref. 47: HgC12); also, Gale and Ferm have demonstrated both fetotoxicity and birth defects in hamsters by exposure to mercuric acetate (Ref. 103). Toxic effects to the human fetus have been documented only with alkyl mercury compounds, mainly methyl mercury. What effects maternal exposure to metallic mercury or inorganic mercury compounds have on the human fetus are unknown. Cleg (Ref. 4 7 ) cites experimental data from mammals to show that transplacental transfer of mercury compounds decreases in the order: methyl > phenyl > inorganic. However, he documents that inorganic mercury is detectable in
the fetal bloodstream. It has been demonstrated that inorganic mercury exerts a deleterious effect on the hamster fetus, but can it also in other mammals? The answer is not known. Also, an interesting statement by Doull (Ref. 37, p. 649) states that methylation of mercury can take place in man (by bacteria in the gut?). If this is so, can inorganic mercury be organified in man to more easily cross the placenta to exert a toxic effect? Little is known about this subject at present. Mr. Laubusch takes offense at ,a statement relating to the number of mercury compound exposures that have led to fetal injury. He has misinterpreted the statement. The article deals specifically with chemical-related birth defects and reproductive failure, not toxicology in general. Can he name one organic compound which has caused more fetal injuries? Three compounds easily come to mind: 1 ) Thalidomide was implicated with 10 000 cases in West Germany; however, this drug, used for therapeutic reasons, is not an environmental pollutant, and therefore was not included in this article. 2) The PCB poisoning incident in Japan involved 13 infants. 3) A case can only be made for diethylstilbestrol, which was a contaminant of beef and poultry. However, no one knows the true number of exposed individuals who ate the meat, or its effect on offspring. The most common effect would be vaginal adenosis, which heals in time via squamous metaplasia. Many would therefore not regard this effect as teratogenic. The contention that methyl mercury itself was dumped into Minimata Bay is false, although even textbooks such as Doull’s is ambiguous on the subject. The factory at Minamata Bay produced nitrogenous fertilizers, vinyl chloride, acetic acid, and H2SO4 (1 ). HgC12 was used as a catalyst in the production of vinyl chloride, and HgS04 in the process for acetaldehyde. Irukayama et al. (2) assayed the seawater from Minimata Bay and confirmed the presence of HgC12, which was predominant, as well as mercuric acetate, vinyl mercuric chloride, HgS04, and metallic mercury. A small amount of organomercurial, also present, was later identified
