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Shorter Menstrual Cycles Associated with Chlorination By-Products in Drinking Water

Shorter Menstrual Cycles Associated with Chlorination By-Products in Drinking Water. Gayle Windham, K Waller, M Anderson, L Fenster, P Mendola, S Swan California Department of Health Services Environmental Health Investigations Branch (Work supported in large part by USEPA).

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Shorter Menstrual Cycles Associated with Chlorination By-Products in Drinking Water

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  1. Shorter Menstrual Cycles Associated with Chlorination By-Products in Drinking Water Gayle Windham, K Waller, M Anderson, L Fenster, P Mendola, S Swan California Department of Health ServicesEnvironmental Health Investigations Branch (Work supported in large part by USEPA)

  2. TTHM Levels and Menstrual Cycling Background • Found association of SAB and high consumption of water with high TTHM and BDCM levels. • Other studies confirm increased risk of adverse pregnancy outcomes with chlorination by-products. Purpose • THMs associated with other reproductive endpoints? • Identify possible mechanisms for the SAB effects. • Examine THM exposure and menstrual cycle function in a study of 400 premenopausal women.

  3. Women’s Reproductive Health Study Methods • Prospective Study of Kaiser members in Santa Clara County • Women “at risk” of pregnancy, married, ages 18-39 • Urine collected daily (about 6 months) to measure: • Steroid metabolites (E1C, PdG) — menstrual cycle function • hCG — early pregnancy loss • Data collected 1990-91 (follow-up 2 years later)

  4. Data Collection Instruments • Screening Interview — phone • eligibility criteria • Baseline Questionnaire — phone • # glasses unheated tap water at home • # glasses hot tap at home • # glasses bottled water/day (and brand) • # showers at home (and length)/week • Demographics and covariates • Daily Diary — self-administered

  5. Individual Hormone Results

  6. Assignment of THM Level • Geocode residence address to identify water utility company • Obtain utility THM monitoring data (total and individual) • Cycle-specific THM levels estimated: • 90-day window, starting 60 days before cycle start • average all utility monitoring points • weighted if moved • average two closest to window, if none during • Woman-level TTHM from average of cycle-specific levels

  7. Results — Subject Characteristics (N=401) % TTHMCharacteristic N % >80 µg/L Age 21-29 years 137 34.2 2 30-34 years 159 39.6 3 35-39 years 105 26.2 4 Race White 283 70.6 3 Hispanic 52 13.0 4 Other 66 16.4 3 Education No College 89 22.2 3 Some College 151 37.7 2 College Graduate 161 40.2 4 Pregnancies 0 48 12.0 4 ≥1, no losses 256 63.8 2 ≥1, ≥1 loss 97 24.2 4

  8. Menstrual Cycle Length Parameters byTotal Trihalomethane Level TTHM Level (µg/L) 0-40 >40-60 >60 Cycle Length Mean (s.e.) 29.7 (0.26) 29.3 (0.28) 28.7 (0.28) Adj. Difference (CI) Ref -0.50 (-1.1, 0.11) -1.1 (-1.8, -0.40) Follicular Phase Mean (s.e.) 16.9 (0.27) 16.5 (0.29) 16.0 (0.30) Adj. Difference (CI) Ref -0.39 (-0.98, 0.20) -0.94 (-1.6, -0.24) Luteal Phase Mean (s.e.) 12.9 (0.09) 12.8 (0.11) 13.0 (0.10) Adj. Difference (CI) Ref -0.08 (-0.33, 0.18) 0.07 (-0.20, 0.35)

  9. Menstrual Cycle Outcomes byTTHM Level % Affected

  10. Length Parameters by Total Trihalomethane Daily Consumption Level TTHM Consumption Level (µg/day) 0 >0-40 >40 Cycle Length N 449 717 458 Mean (s.e.) 29.8 (0.39) 29.43 (0.28) 28.5 (0.33) Adj. Difference (CI) Ref -0.23 (-1.2, 0.77) -1.1 (-2.2, -0.06) Follicular Phase N 402 676 436 Mean (s.e.) 17.1 (0.43) 16.6 (0.30) 15.8 (0.34) Adj. Difference (CI) Ref -0.32 (-1.4, 0.77) -1.1 (-2.2, 0.03)

  11. Length Parameters by Quartiles of Chloroform and Brominated Trihalomethane Levels Quartile of Exposure 1 2-3 4 Mean in Days Difference Difference (s.e.) (95% CI) (95% CI) Cycle Length Chloroform 29.6 (0.30) -0.43 (-0.99, 0.13) -0.30 (-1.0, 0.40) Sum of Brominated 30.0 (0.34) -0.72 (-1.4, -0.04) -1.2 (-2.0, -0.40) Follicular Phase Chloroform 16.8 (0.31) -0.42 (-0.96, 0.12) -0.13 (-0.82, 0.56) Sum of Brominated 17.2 (0.35) -0.66 (-1.3, 0.02) -1.1 (-1.9, -0.29)

  12. TTHM Levels and Menstrual Cycling Strengths • Prospective study • TTHM exposure from existing records in narrow time frame • Information on some water use patterns • Endpoint determined from biologic measures (vs. self-report) • Adjusted for several potential confounders • First study of reproductive function in non-pregnant women Limitations • Potential exposure misclassification (utility average) • No information on exposure outside the home • Study sample may not represent full range of cycle variability

  13. Conclusions and Summary • Increasing TTHM level is associated with decreasing cycle length, primarily in the follicular phase • This decrease is associated with the brominated THMs, primarily chlorodibromomethane • Combining consumption and TTHM level reveals similar, but not greater, associations • Accounting for showering also does not reveal stronger associations Confirm effects on ovarian function in other studies

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