exposed workers in coiling and wire drawing. An association with any exposure to solvents was found among aircraft-maintenance workers (SMR=1.6, 95% CI=0.9–2.8) (Blair et al., 1998). No associations were found in studies of workers exposed to aromatic or halogenated solvents (Anttila et al., 1995, 1998), in patients with solvent-related disorders (Berlin et al., 1995), and in aircraft-manufacturing workers (Garabrant et al., 1988).

Summary and Conclusion

In most occupational settings, multiple solvent exposures occurred, so exposures to specific solvents may be highly correlated. Because many studies used occupational titles as exposure surrogates, the ability to assess an association between specific solvents and breast cancer risk was compromised.

A number of studies assessed breast cancer risk and solvent exposure in general, and others provided exposure estimates for specific individual solvents, such as trichloroethylene, tetrachloroethylene, dry-cleaning solvents, benzene, and methylene chloride. The evidence was limited by nonspecific exposure assessments and a reliance on mortality from breast cancer. Nondifferential misclassification of exposure, poor control for confounding, and low statistical power due to small numbers were additional limitations. Table 6.21 identifies the key studies and relevant data points reviewed by the committee in drawing its conclusion. Unless indicated in the tables, the study populations include both men and women.

The committee concludes, from its assessment of the epidemiologic literature, that there is inadequate/insufficient evidence to determine whether an association exists between chronic exposure to solvents under review and breast cancer.

TABLE 6.21 Selected Epidemiologic Studies—Breast Cancer and Exposure to Organic Solvents


Study Population

Exposed Cases

Estimated Relative Risk (95% CI)


Cohort Study—Incidence

Hansen et al., 2001

Biologically monitored workers in Denmark



Females, ever exposed


0.9 (0.2–2.3)

Cohort Studies—Mortality

Boice et al., 1999

Aircraft-manufacturing workers in California



Potential routine exposure


1.31 (0.53–2.69)

Blair et al., 1998

Aircraft-maintenance workers in Utah (females)



Any exposure


1.8 (0.9–3.3)


Low, continuous


3.4 (1.4–8.0)


Frequent peaks


1.4 (0.7–3.2)

Morgan et al., 1998

Aerospace workers in Arizona


Ever exposed


0.75 (0.43–1.22)


Low exposure


1.03 (0.51–1.84)


High exposure


0.47 (0.15–1.11)

Anttila et al., 1995

Finnish workers biologically monitored for exposure to halogenated hydrocarbons


0.85 (0.59–1.18)

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