Warming drinking water distribution systems in the context of climate change: a scoping review on health-related microbial and chemical water quality effects.

Background: Warming caused by climate change can impact human health risks associated with drinking water. This review aimed to synthesize the evidence about the effects of increasing temperatures in the drinking water distribution system (DWDS) on health-related chemical and microbial water quality parameters. We also identified adaptation options. Methods: We conducted a scoping review of quantitative peer-reviewed studies published up to March 2023, and research reports published up to April 2024, specifically looking at a DWDS or comparable experimental conditions. Results: We included 28 studies in this review. Evidence focused on chlorinated systems in higher-income countries. Warming has variable effects on microbial communities within the DWDS. Accumulation and release of heavy metals may increase at higher temperatures, depending on pipe materials. Warming also speeds up the decay of chlorine and chloramine, affecting the formation of disinfectant byproducts and the potential of microbial (re)growth. Multiple effects can occur simultaneously, requiring an integrated adaptation approach. Technical and institutional adaptation options, such as improved removal of dissolved organic carbon during treatment covering the entire DWDS were identified. Discussion: With increasing climate change, the identified effects can become more prominent without adaptation. However, no included studies quantified how these effects would translate into human health impacts.