Evidence From Humans
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Assessing the underlying breast cancer risk of Chinese females contributed by dietary intake of residual DDT from agricultural soils
Tang, M., Zhao, M., Shanshan, Z., Chen, K., Zhang, C., Liu, W. Environ Int. 2014. 73, 208-15.
Topic area
Environmental pollutant - DDT DDE
Study design
Population-based case-control
Funding agency
National Natural Science Foundation of China
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number of Controls
Controls: 72
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Cases were identified from cancer and death registries in Jiaxing county of Zhejiang province from 2005-2007. One control from the same county was selected for each case.
Comment about participation selection
The lack of information about control selection limits assessment of whether controls were representative of population that gave rise to cases.
Exposure Investigated
Exposures investigated
Participants' serum samples were analyzed for p,p'-DDE, p,p'-DDT, and sum DDT in the case-control study. Separately, DDT was measured in soil samples from agricultural fields in 132 cities across 32 provinces of China. Population-weighted concentrations
How exposure was measured
Biological Environmental sample
Exposure assessment comment
There is no mention of serum lipids in the case-control analysis, however DDT metabolite levels are reported as "ng/g", suggesting that the levels are lipid-adjusted. Treatment status of cases not specified. Serum collected at the time of diagnosis may not capture exposure relevant to development of breast cancer.
Breast cancer outcome investigated
Primary incident breast cancer
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.
Age, BMI, occupation, education
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Strength of associations reported
≥ 75th percentile vs < 75th percentile:
p,p'-DDE: aOR 2.52 (95% CI 1.19-5.31)
p,p'-DDT: aOR 1.42 (95% CI 0.69-2.92)
sum DDT: aOR 1.95 (95% CI 0.95-4.00)
Results Comments
The estimated serum p,p-DDE exposure levels across China using (1) the population-weighted soil measures, (2) the bioaccumulation frequency (BAF) for p,p'-DDE from soil to serum from a separate study, and (3) Odds Ratio from the case-control analysis. The serum estimates were then used to compute risk ratios for p,p'-DDE across the provinces where soil measures were obtained. Finally, population attributable fractions (PAFs) were computed based on these estimated risk ratios. Estimated PAFs ranged widely from 0.0002 - 73%.
Author address
Ministry of Education Key Laboratory of Environmental Remediation & Ecosystem Health, College of Environmental and Research Sciences, Zhejiang University, Hangzhou, China. International Joint Research Center for Persistent Toxic Substances, Zhejiang Unive
Reviewers Comments
Regional-level risk factors (e.g. diet, tobacco use) were not considered in the calculation of the population attributable fraction (PAF). Other concerns include the fact that the PAF calculations relied on the Odds Ratio from the case-control study, which may not have used appropriate controls (too little information to tell) and also used a BAF from a separate study of mothers and children in Tianjin, China. The average serum levels measured in the Tianjin study (1.64 ng/mL) may not be representative of serum levels in the larger Chinese population.
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