Evidence From Humans
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Female breast cancer and trihalomethane levels in drinking water in North Carolina
Marcus, P. M., Savitz, D. A., Millikan, R. C., Morgenstern, H. Epidemiology. 1998. 9:2, 156-60.
Topic area
Environmental pollutant - Drinking water
Study design
Other: Ecologic epidemiology
Funding agency
NCI Other: Environment and Breast Cancer Program
Study Participants
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
71 North Carolina water suppliers serving at least 10,000 customers in 1995; excluded military, municipality with multiple suppliers, and outlier
Exposure Investigated
Exposures investigated
Trihalomethanes in drinking water. 1993-1994 average THM levels from quarterly reports to NC Dept. Env. Health & Natural Resources were assigned to zip codes.
How exposure was measured
GIS/geographic location Environmental sample
Exposure assessment comment
Exposure measured near time of diagnosis; ecologic
Statistical Analysis
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
African Americans
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
By water supply geographic unit: age, annual income, % with > 12 years education, % urban, % black
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Poisson regression to estimate rate ratios
Strength of associations reported
RR for highest compared to lowest: whites 1.1 (0.9 -1.3) blacks 1.2 (0.8-1.8)
When restricted to supplies that serve at least 50% of the population: whites 1.0(0.8-1.3) blacks 1.3(0.9-1.9)
When restricted to supplies where 75% of the population is in the same house or county as in 1985: whites 1.1(0.9-1.3), blacks 1.2 (0.8-1.8)
Restricted to cases over 50: total 1.1(0.9-1.3) results do not differ by race
Results Comments
Exposure measure is weak for multiple reasons.
Author address
Department of Epidemiology, University of North Carolina at Chapel Hill, USA.
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