Studies investigating exposure to disinfection by-products (DBPs) via chlorinated waters during
pregnancy and adverse fetal growth outcomes have been limited by potential exposure measurement
error, lack of exposure assessment validation and potential residual confounding. Factors driving
DBP exposure are poorly understood, making it difficult to target resources appropriately in order to
improve exposure assessment. These issues were investigated through DBP exposure assessment
and validation for a new investigation of DBPs and fetal growth within the Born in Bradford (BiB)
cohort study.
Analysis of individual water use in the BiB cohort found that water consumption, showering,
bathing and swimming varied by demographic and lifestyle factors. Sampling, analysis, and
modelling of trihalomethanes (THMs) in tap water showed that THM concentrations exhibited clear
seasonal variation, but spatial variability was limited across the study area. Various metrics of
exposure to THMs during pregnancy were created, including ‘personalised’ semi-individual
metrics. Analysis of these metrics revealed individual water use to be the main driver of THM
exposure in this cohort, with spatial and temporal variability having little influence. Compared with
a fully integrated THM exposure metric (incorporating ingestion, showering/bathing and
swimming), metrics based only on THM concentrations or THM ingestion misclassified over 50%
of women. A nested validation study was conducted using a 7-day water diary and urinary
trichloroacetic acid (TCAA) biomarker. This found error in self-reported water use and TCAA
ingestion estimates to vary by employment status - error being greater for employed women.
Urinary TCAA was not correlated with TCAA in tap water, reinforcing that individual water use is
the most influential driver of DBP exposure in this cohort.
Recommendations for future research include improved individual water use assessment covering
more activities and time-points in pregnancy, stratified analysis of questionnaire validation studies,
and use of urinary TCAA as a main exposure measure in epidemiological studies.