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Progress in Chronic Disease Prevention Reduction of Children's Arsenic Exposure Following Relocation -- Mill Creek, Montana

Soil in the communities surrounding Anaconda, Montana, remains contaminated with arsenic, even though the copper smelter located there has been closed since 1980. Because of concern that children might be exposed to arsenic by hand-to- mouth activity, those who lived near the smelter and were between 2 and 6 years of age were tested for urinary arsenic in March and again in July 1985.

Children living in the small community of Mill Creek, which had the highest levels of arsenic in soil, had elevated levels of urinary arsenic at both testings. Their mean level of urinary arsenic was 66.0 ugmg/l in March and 54.1 ugmg/l in July. (In the control community of Livingston, Montana, mean levels of urinary arsenic were 10.6 ugmg/l in March and 16.6 ugmg/l in July.) Since a level of 50 ugmg/l has been considered indicative of excess exposure in the past (1), additional urine samples were obtained between July and November 1985. The children's levels of urinary arsenic remained elevated. In the summer of 1986, the U.S. Environmental Protection Agency temporarily relocated 10 Mill Creek families until a permanent solution to the problem could be developed.

To evaluate the effect of relocation on levels of urinary arsenic, urine samples were obtained from as many members of the families being relocated as possible. Each individual was asked to supply a total of six urine samples taken upon waking up in the morning. Three were to be taken in July, before relocation, and three, afterward, in October. Levels of urinary arsenic were measured using atomic absorption spectrophotometry. The average pre- and post-move concentrations of urinary arsenic were calculated for each person. These averages were used to calculate group averages.

Forty-one persons provided at least one urine sample. Four of these people did not move from Mill Creek. Thirty-two of the 37 people who were relocated provided samples both before and after relocation. The average pre-move level of urinary arsenic for the 6 relocated children who were less than8 years of age was 76.0 ugmg/l; their average post-move level was 15.3ugmg/l. The average pre-move level for persons greater than or equal to8 years of age was 17.2 ugmg/l; their average post-move level was 14.6 ugmg/l. Although five individuals had levels of urinary arsenic greater than50 ugmg/l prior to the move, none had levels greater than50 ugmg/l after relocation from Mill Creek. Reported by: JK Gedrose, MN, State Epidemiologist, Montana State Dept of Health and Environmental Sciences. Div of Environmental Hazards and Health Effects, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: Arsenic is believed to be potently carcinogenic, both through ingestion and through inhalation. About 70 of a daily dose of arsenic, which has a half-life of 10-30 hours, is eliminated in the urine in a biphasic manner (2). Levels of urinary arsenic are generally considered the best indicators of exposure to arsenic occurring within the few days preceding testing (3).

Mean levels of urinary arsenic among Mill Creek residents decreased after relocation. However, relocation is a controversial strategy for reducing exposure to environmental contaminants. A decision about the long-term management of the contamination in Mill Creek has not yet been reached.

The finding that children's pre-move levels of urinary arsenic were so much greater than the levels of adults is consistent with the hypothesis that the children were being exposed to arsenic through ingestion of soil. As with lead poisoning, hand-to-mouth activity is believed to be the primary route of exposure. The results of testing in Mill Creek indicate that children can serve as a sentinel population for nonoccupational exposure to environmental hazards when the primary pathway is through soil ingestion.


  1. Landrigan PJ. Arsenic. In: Rom WN, ed. Environmental and occupational medicine. Boston, Massachusetts: Little, Brown and Company, 1983:473-9.

  2. Crecelius EA. Changes in chemical speciation of arsenic after ingestion by man. Environ Health Perspect 1977;19:147-50.

  3. Lauwerys RR. Industrial chemical exposure: guidelines for biological monitoring. Davis, California: Biomedical Publications, 1983.

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