Academic journal article Environmental Health Perspectives

DDT and Breast Cancer in Young Women: New Data on the Significance of Age at Exposure

Academic journal article Environmental Health Perspectives

DDT and Breast Cancer in Young Women: New Data on the Significance of Age at Exposure

Article excerpt

BACKGROUND: Previous studies of DDT and breast cancer assessed exposure later in life when the breast may not have been vulnerable, after most DDT had been eliminated, and after DDT had been banned.

OBJECTIVES: We investigated whether DDT exposure in young women during the period of peak DDT use predicts breast cancer.

METHODS: We conducted a prospective, nested case-control study with a median time to diagnosis of 17 years using blood samples obtained from young women during 1959-1967. Subjects were members of the Child Health and Development Studies, Oakland, California, who provided blood samples 1-3 days after giving birth (mean age, 26 years). Cases (n = 129) developed breast cancer before the age of 50 years. Controls (n = 129) were matched to cases on birth year. Serum was assayed for p,p'-DDT, the active ingredient of DDT; o,p'-DDT, a low concentration contaminant; and p,p'-DDE, the most abundant p,p'-DDT metabolite.

RESULTS: High levels of serum p,p'-DDT predicted a statistically significant 5-fold increased risk of breast cancer among women who were born after 1931. These women were under 14 years of age in 1945, when DDT came into widespread use, and mostly under 20 years as DDT use peaked. Women who were not exposed to p,p'-DDT before 14 years of age showed no association between p,p'-DDT and breast cancer (p = 0.02 for difference by age).

CONCLUSIONS: Exposure to p,p'-DDT early in life may increase breast cancer risk. Many U.S. women heavily exposed to DDT in childhood have not yet reached 50 years of age. The public health significance of DDT exposure in early life may be large.

KEY WORDS: breast cancer, child health and development studies, exposure timing, o,p'-DDT, organochlorines, p,p'-DDE, p,p'-DDT, pregnancy, premenopausal. Environ Health Perspect 115:1406-1414 (2007). doi:10.1289/ehp.10260 available via http://dx.doi.org/ [Online 24 July 2007]

Most previous studies do not support the hypothesis that exposure to DDT is an important risk factor for breast cancer (Lopez-Cervantes et al. 2004). However, previous studies were limited by the inability to measure exposure in young women during periods of the heaviest DDT use. Consequently most of these studies observed very low levels of p,p'-DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and o,p'-DDT [1,1,1-trichloro-2-(p-chlorophenyl)-2-(o-chloro-phenyl)ethane], the primary constituents of commercial DDT (Table 1). The conclusions of these studies apply to the effects of p,p'-DDE [1,1'-dichloro-2,2'-bis(p-chloro-phenyl)ethylene], the primary metabolite of p,p'-DDT (Lopez-Cervantes et al. 2004), which is more persistent in the environment and in biological systems and can therefore be measured years after DDT use had declined (Stehr-Green 1989).

Table 1. Studies of blood levels of DDT-related compounds
and breast cancer.

Year            Place             Design        Age at Blood
of blood draw                                   draw (years)

1963           N. California      Prospective,       26
               (CHDS; present     median
               study)             follow-up 17
                                  years

1967           N. California      Prospective,       45
               (Krieger et        mean follow-up
               al. 1994)          14 years

1974           Maryland           Prospective        20%
or             (Helzlsouer et     follow-up          [less
1989           al. 1999)          [greater than or   than or
                                  equal to]          equal to] 40
                                  10 years for       (1974) 2.9%
                                  70%                [less than
                                                     or equal to]
                                                     40 (1989)

1979           Norway (Ward et    Prospective,       41
               al. 2000)          mean follow-up
                                  9 years

1977           Copenhagen,        Prospective,       55 (1977) 60
or             Denmark (Hoyer     mean follow-up
1982           et al. … 
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