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Spatial variations in the incidence of breast cancer and potential risks associated with soil dioxin contamination in Midland, Saginaw, and Bay Counties, Michigan, USA.

Dai D, Oyana TJ - Environ Health (2008)

Bottom Line: High levels of dioxins in soil and higher-than-average body burdens of dioxins in local residents have been found in the city of Midland and the Tittabawassee River floodplain in Michigan.High levels of dioxin in soils were observed in the city of Midland and the Tittabawassee River 100-year floodplain.Findings can be used for heightened surveillance and education, as well as formulating new study hypotheses for further research.

View Article: PubMed Central - HTML - PubMed

Affiliation: Environmental Resources and Policy Program, Southern Illinois University, 405 West Grand Avenue, MC 4637, Carbondale, IL 62901-4637, USA. ddai@niu.edu

ABSTRACT

Background: High levels of dioxins in soil and higher-than-average body burdens of dioxins in local residents have been found in the city of Midland and the Tittabawassee River floodplain in Michigan. The objective of this study is threefold: (1) to evaluate dioxin levels in soils; (2) to evaluate the spatial variations in breast cancer incidence in Midland, Saginaw, and Bay Counties in Michigan; (3) to evaluate whether breast cancer rates are spatially associated with the dioxin contamination areas.

Methods: We acquired 532 published soil dioxin data samples collected from 1995 to 2003 and data pertaining to female breast cancer cases (n = 4,604) at ZIP code level in Midland, Saginaw, and Bay Counties for years 1985 through 2002. Descriptive statistics and self-organizing map algorithm were used to evaluate dioxin levels in soils. Geographic information systems techniques, the Kulldorff's spatial and space-time scan statistics, and genetic algorithms were used to explore the variation in the incidence of breast cancer in space and space-time. Odds ratio and their corresponding 95% confidence intervals, with adjustment for age, were used to investigate a spatial association between breast cancer incidence and soil dioxin contamination.

Results: High levels of dioxin in soils were observed in the city of Midland and the Tittabawassee River 100-year floodplain. After adjusting for age, we observed high breast cancer incidence rates and detected the presence of spatial clusters in the city of Midland, the confluence area of the Tittabawassee, and Saginaw Rivers. After accounting for spatiotemporal variations, we observed a spatial cluster of breast cancer incidence in Midland between 1985 and 1993. The odds ratio further suggests a statistically significant (alpha = 0.05) increased breast cancer rate as women get older, and a higher disease burden in Midland and the surrounding areas in close proximity to the dioxin contaminated areas.

Conclusion: These findings suggest that increased breast cancer incidences are spatially associated with soil dioxin contamination. Aging is a substantial factor in the development of breast cancer. Findings can be used for heightened surveillance and education, as well as formulating new study hypotheses for further research.

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Study area. The study area shows sampling locations and corresponding dioxin levels, Tittabawassee River and its floodplain, and major cities. Michigan soil generic residential direct contact criterion for dioxins (RDCC) is 90 ppt TEQ.
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Figure 1: Study area. The study area shows sampling locations and corresponding dioxin levels, Tittabawassee River and its floodplain, and major cities. Michigan soil generic residential direct contact criterion for dioxins (RDCC) is 90 ppt TEQ.

Mentions: Previous studies have reported higher than normal levels of dioxins in some locations in the city of Midland and Tittabawassee River floodplain in Michigan (Figure 1); while dioxin concentration in soils upstream of the river is similar to background levels across Michigan [1-5]. The most probable historic source of dioxins in the river is located in the city of Midland from industrial processes in the Dow Chemical Company's (Dow) Midland plant [2,3,6,7]. As by-products in chlorine-based chemical processes, dioxins were released into the air and water decades ago and accumulated in the sediments and soils in and near the Tittabawassee River [1,3]. Floods then swept and redeposited sediments and soils within the floodplain. Recent studies [8] found that living on property with soils contaminated by dioxins and eating fish from the Tittabawassee River, the Saginaw River, and Saginaw Bay led to higher levels of dioxins in people's blood. Inspired by the increased concern regarding the possible health effects, this study aimed at evaluating the soil dioxin contamination and exploring the potential risks associated with breast cancer incidence in the region.


Spatial variations in the incidence of breast cancer and potential risks associated with soil dioxin contamination in Midland, Saginaw, and Bay Counties, Michigan, USA.

Dai D, Oyana TJ - Environ Health (2008)

Study area. The study area shows sampling locations and corresponding dioxin levels, Tittabawassee River and its floodplain, and major cities. Michigan soil generic residential direct contact criterion for dioxins (RDCC) is 90 ppt TEQ.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2577707&req=5

Figure 1: Study area. The study area shows sampling locations and corresponding dioxin levels, Tittabawassee River and its floodplain, and major cities. Michigan soil generic residential direct contact criterion for dioxins (RDCC) is 90 ppt TEQ.
Mentions: Previous studies have reported higher than normal levels of dioxins in some locations in the city of Midland and Tittabawassee River floodplain in Michigan (Figure 1); while dioxin concentration in soils upstream of the river is similar to background levels across Michigan [1-5]. The most probable historic source of dioxins in the river is located in the city of Midland from industrial processes in the Dow Chemical Company's (Dow) Midland plant [2,3,6,7]. As by-products in chlorine-based chemical processes, dioxins were released into the air and water decades ago and accumulated in the sediments and soils in and near the Tittabawassee River [1,3]. Floods then swept and redeposited sediments and soils within the floodplain. Recent studies [8] found that living on property with soils contaminated by dioxins and eating fish from the Tittabawassee River, the Saginaw River, and Saginaw Bay led to higher levels of dioxins in people's blood. Inspired by the increased concern regarding the possible health effects, this study aimed at evaluating the soil dioxin contamination and exploring the potential risks associated with breast cancer incidence in the region.

Bottom Line: High levels of dioxins in soil and higher-than-average body burdens of dioxins in local residents have been found in the city of Midland and the Tittabawassee River floodplain in Michigan.High levels of dioxin in soils were observed in the city of Midland and the Tittabawassee River 100-year floodplain.Findings can be used for heightened surveillance and education, as well as formulating new study hypotheses for further research.

View Article: PubMed Central - HTML - PubMed

Affiliation: Environmental Resources and Policy Program, Southern Illinois University, 405 West Grand Avenue, MC 4637, Carbondale, IL 62901-4637, USA. ddai@niu.edu

ABSTRACT

Background: High levels of dioxins in soil and higher-than-average body burdens of dioxins in local residents have been found in the city of Midland and the Tittabawassee River floodplain in Michigan. The objective of this study is threefold: (1) to evaluate dioxin levels in soils; (2) to evaluate the spatial variations in breast cancer incidence in Midland, Saginaw, and Bay Counties in Michigan; (3) to evaluate whether breast cancer rates are spatially associated with the dioxin contamination areas.

Methods: We acquired 532 published soil dioxin data samples collected from 1995 to 2003 and data pertaining to female breast cancer cases (n = 4,604) at ZIP code level in Midland, Saginaw, and Bay Counties for years 1985 through 2002. Descriptive statistics and self-organizing map algorithm were used to evaluate dioxin levels in soils. Geographic information systems techniques, the Kulldorff's spatial and space-time scan statistics, and genetic algorithms were used to explore the variation in the incidence of breast cancer in space and space-time. Odds ratio and their corresponding 95% confidence intervals, with adjustment for age, were used to investigate a spatial association between breast cancer incidence and soil dioxin contamination.

Results: High levels of dioxin in soils were observed in the city of Midland and the Tittabawassee River 100-year floodplain. After adjusting for age, we observed high breast cancer incidence rates and detected the presence of spatial clusters in the city of Midland, the confluence area of the Tittabawassee, and Saginaw Rivers. After accounting for spatiotemporal variations, we observed a spatial cluster of breast cancer incidence in Midland between 1985 and 1993. The odds ratio further suggests a statistically significant (alpha = 0.05) increased breast cancer rate as women get older, and a higher disease burden in Midland and the surrounding areas in close proximity to the dioxin contaminated areas.

Conclusion: These findings suggest that increased breast cancer incidences are spatially associated with soil dioxin contamination. Aging is a substantial factor in the development of breast cancer. Findings can be used for heightened surveillance and education, as well as formulating new study hypotheses for further research.

Show MeSH
Related in: MedlinePlus