Methodical approaches to raising the reliability of health risk assessment when using polymer materials in drinking water supply

Plastic pipes and coatings may contain additives, including metal stabilizers and antioxidants, designed to protect the material during manufacture and use. Some chemical compounds can be released from these plastic pipes and affect quality of drinking water. The article focuses on analyzing various approaches to examining polymer materials with the aim to assess migration of chemicals into drinking water. These approaches usually underlie methodologies of hygienic assessment developed for polymers. Migration was assessed under the same conditions as per two types of migration processes, a continuous and a sequential one. These two types of migration processes emulate conditions typical for different flows in drinking water pipelines: situations of continuous stagnation in the system and a standard flow when water is renewed regularly in water supply networks. More than 20 organic compounds were identified in tested water samples. Most of them occurred in small concentrations (excluding benzenesulfonic acid butyl amide). Moreover, many of these chemicals are not regulated in drinking water, there no standards or reference concentrations fixed for them or a relevant toxicological assessment. Given that, it is practically impossible to assess health risks caused by exposure to these chemicals according to conventional assessment procedures. It was also shown that release of chemicals differed considerably under different experimental designs. The results produced by successive migration tests indicated that intensity of migration from polymer materials the pipes were made from tended to change over time whereas the results of continuous migration tests showed that in case of stagnation quality of drinking water could deteriorate rather rapidly due to migration of organic compounds.