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Abstract
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At approximately 5:45 pm on March 24, 1976, several residents of Chattanooga noticed that their tap water had suddenly turned white and smelled of insecticide. By the following day it was established that a 3-street area was affected, and the water supply was promptly cut off by the water company. Samples of water taken on the evening of March 24 revealed Chlordane as the contaminant in concentrations up to 1,200,000 parts per billion.
A house-to-house survey, conducted on March 26 and 27, reached 45 of the 49 affected households (92%). One hundred and twelve persons were questioned, and 17 (15%) gave a history of having drunk the suspect water, while another 15 (13%) had casual contact through washing, bathing, or brushing teeth. Blood samples for Chlordane analyses were obtained from 71 persons who gave a history of water contact or who had symptoms possibly related to Chlordane toxicity.
Four persons gave a history of probable Chlordane toxicity, that is, gastrointestinal symptoms such as nausea, vomiting, abdominal pain, in addition to evidence of neurologic involvement such as dizziness, blurred vision, irritability, headache, paresthesias, muscle weakness, or twitching. Nine other persons had gastrointestinal symptoms alone or isolated neurologic symptoms. One of the suspect cases developed a fever of 102°F; she had recently recovered from an episode of intrahepatic cholestasis. None of the residents was hospitalized, and all affected persons improved within 36-48 hours after exposure.
Results of quantitative analyses for Chlordane in water focused attention on a section of one affected street as the possible source of contamination. A strong smell of chlordane came from the foundation of a house there, and soil samples from around that house were found to contain chlordane in concentrations of greater than 1,000,000 parts per billion. Further questioning of the residents established that chlordane had been used at the house on March 24 for extermination of termites. The concentrated chlordane solution had been diluted with tap water approximately 90 minutes before chlordane was detected down- stream in the water system.
Blood analyses on the 13 individuals with symptoms revealed measurable levels of transnonachlor, a chlordane metabolite, in 11 (85%). The highest level, 1.27 parts per billion, was recorded in the 1 individual who also had the only detectable oxychlordane level (0.37 parts per billion). Results of blood tests on the remaining 58 exposed individuals are pending.
The water company has replaced all the street pipes and is in the process of flushing each house in an attempt to remove residual chlordane.
Editorial Note: This appears to be the first recorded incident of chlordane contamination of a public water supply in which symptoms of toxicity have been cited. The exact mode of entry of the pesticide into the water supply is not clear. The most likely explanation is that back siphonage of chlordane occurred during the process of diluting the pesticide when the hose from the water faucet dipped below the level of the concentrated chlordane. Such an explanation is quite possible because several main pipes had been broken the preceding week by building contractors, causing variable water pressure in the system. The significance of the chlordane levels in this exposed population is difficult to assess. Oxychlordane and transnonachlor are recently discovered metabolites of chlordane, and review of the literature reveals no population studies of chlordane levels to date. |