title: Identifying public water facilities with low spatial variability of disinfection by-products for epidemiological investigations.
abstract: OBJECTIVE
  Epidemiological studies of disinfection by-products (DBPs) and reproductive outcomes have been hampered by misclassification of exposure. In most epidemiological studies conducted to date, all persons living within the boundaries of a water distribution system have been assigned a common exposure value based on facility-wide averages of trihalomethane (THM) concentrations. Since THMs do not develop uniformly throughout a distribution system, assignment of facility-wide averages may be inappropriate. One approach to mitigate this potential for misclassification is to select communities for epidemiological investigations that are served by distribution systems with consistently low spatial variability of THMs.
  
  
  RESULTS
  A feasibility study was conducted to develop methods for community selection using the Information Collection Rule (ICR) database, assembled by the US Environmental Protection Agency. The ICR database contains quarterly DBP concentrations collected between 1997 and 1998 from the distribution systems of 198 public water facilities with minimum service populations of 100,000 persons. Facilities with low spatial variation of THMs were identified using two methods; 33 facilities were found with low spatial variability based on one or both methods. Because brominated THMs may be important predictors of risk for adverse reproductive outcomes, sites were categorised into three exposure profiles according to proportion of brominated THM species and average TTHM concentration. The correlation between THMs and haloacetic acids (HAAs) in these facilities was evaluated to see whether selection by total trihalomethanes (TTHMs) corresponds to low spatial variability for HAAs. TTHMs were only moderately correlated with HAAs (r = 0.623).
  
  
  CONCLUSIONS
  Results provide a simple method for a priori selection of sites with low spatial variability from state or national public water facility datasets as a means to reduce exposure misclassification in epidemiological studies of DBPs.
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523-1681, USA. ahinckley@cdc.gov
authors.forename: A F
authors.initials: AF
authors.lastname: Hinckley
authors.forename: A M
authors.initials: AM
authors.lastname: Bachand
authors.forename: J R
authors.initials: JR
authors.lastname: Nuckols
authors.forename: J S
authors.initials: JS
authors.lastname: Reif
mesh_terms: D019342:Acetic Acid / Q000032:analysis; D000704:Analysis of Variance; D016208:Databases, Factual; D004202:Disinfectants / Q000032:analysis*; D004781:Environmental Exposure; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D018811:Maternal Exposure; D011247:Pregnancy; D022882:Trihalomethanes / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000592:standards*; D014881:Water Supply / Q000592:standards
chemical_list: D004202:Disinfectants; D022882:Trihalomethanes; D014874:Water Pollutants, Chemical; D019342:Acetic Acid