The overall aim is to investigate potential human health risks (e.g. cancer, premature births, small for gestational age, semen quality, still birth, congenital anomalies) associated with long-term exposure to low levels of disinfectants (such as chlorine) and disinfectant by-products (DBPs) occurring in water for human consumption and use in the food industry. The study will comprise risk/benefit analyses including quantitative assessments of risk associated with microbial contamination of drinking water versus chemical risk and will compare alternative treatment options. The outcome will be improved risk assessment/management. The study will make use of existing studies/databases and newly collected information.

The specific objectives of the proposed work are as follows:

1. To determine the disinfection by-product (DBP) composition and levels in drinking water in various regions in Europe. Initially a literature survey will be carried out and organisations contacted to obtain information on DBPs in Europe. Representative water samples will be collected in the regions where the epidemiological studies are carried out and other regions, to give a wider picture on their presence and levels. Samples will be analysed for trihalomethanes (THM) (including chloroform, bromodichloromethane, chlorodibromomethane and bromoform), haloacetonitriles (HANs) (including chloroacetonitrile, dichloroacetonitrile, trichloroacetonitrile, bromoacetonitrile, dibromoacetonitrile, tribromoacetonitrile, chlorobromoacetonitrile, dichlorobromoacetonitrile and dibromochloroacetonitrile), haloacetic acids (HAAs) (including chloroacetic acid, dichloroacetic acid, trichloroacetic acid, dibromoacetic acid, tribromoacetic acid, dibromochloroacetic acid, chlorobromoacetic acid, bromoacetic acid, dichlorobromoacetic acid), haloaketones (HAKs) (including 1,1-dichloropropanone, 1,3-dichloropropanone, 1,1,1-trichloropropanone), MX, chlorate hydrate (CH), chloropicrin (CP), bromate, chlorite and chlorate, depending on the type of water disinfectant treatment used. The consortium will produce a database containing the levels of these DBPs in the various regions.
2. To identify the determinants of DBPs and develop predictive models. In addition to the DBP analysis for a range of DBPs (see objective I), the consortium will obtain information regarding the possible determinants of the DBPs including organic matter content, water source, temperature, pH, (residual) disinfectant levels e.g chlorine and bromide level. Statistical techniques will be employed to quantify the effect of these determinants on the formation of DBPs and use this to build a predictive model of DBP formation. Furthermore, the correlation between trihalomethanes and other DBPs will be assessed.

3. To assess the risk of reproductive effects in relation to disinfection practices and levels of disinfection by-products, we will conduct epidemiological studies to examine the relationship between DBPs and the following outcomes:

   • Congenital anomalies, including neural tube, major heart, major stomach wall, and urinary tract defects, cleft palate/lip, and still birth in an intervention study and a large nation wide cross sectional study, using registry data in the UK, where mainly chlorination is used as a disinfectant.
   • Congenital anomalies, including neural tube, major heart, and urinary tract defects using registry data in Italy in regions, where mainly chlorine dioxide is used as a disinfectant.
   • Small for gestational age and premature birth in birth cohorts in Spain, Greece, France and Lithuania, where a range of treatments are used. We will also examine gene-environment interactions (e.g. CYP2E1, GSTT1) in these populations. The work is conducted as part of WP 4 and deliverables are D9 and D10 (see WPs and deliverables list).
   • Semen quality, using a case control design in the UK, where mainly chlorination is used for water disinfection.

   Information will also be collected on potential confounding variables. Statistical regression analysis will be used to assess and describe the exposure response relationships, if any. These population-based studies will also provide estimates of the public health impact of exposure to DBPs in various populations, so that the risk estimates and policy implications can be based on empirical evidence.

4. To assess the risk of cancer, particularly bladder cancer and colon cancer, in relation to disinfection by-product practices and disinfection by-products levels, including the examination of any gene-environment interactions (e.g. CYP2E1, GSTT1). The study will obtain risk estimates from existing bladder case control cancer studies in Spain, France (includes ozonation as treatment) and Finland, and a published meta-analysis.
   
   Epidemiological studies will be conducted, using a case control design to examine the relationship between DBPs and colon cancer in Spain and Italy. The work is conducted as part of WP7 and deliverables are D15 and D16 (see WPs and deliverables list).
5. To conduct risk/benefit analyses including quantitative assessments of risk associated with microbial contamination of drinking water versus chemical risk, compare alternative treatment options, and produce burden of disease estimates (e.g. DALYs). It will build on and make use of expertise and experience of EC funded projects such as MICRORISK and INTARESE.
6. The water and health policies in Europe, USA and worldwide will be reviewed in relation to water disinfection. Best practice in terms of water disinfection and a brief assessment of disinfection alternatives will complete the study. The final workshop, organised as an open conference will aim to bring together scientists working on environmental, toxicological, epidemiological and policy aspects of chlorination DBPs, microbiologists, policy makers, and representatives from the water industry and consumer organisations in Europe to develop guidelines for policy across Europe and the future research agenda.
7. To assess the policy implications of current disinfection practices, taking into account recent environmental, toxicological and epidemiological findings and the findings of the proposed study. These various aspects will be examined, including the measurement and modelling of DBPs and the results of the epidemiological and risk/benefit studies.