Water system plastic pipes and storage tanks are commonly used in construction due to their ease of installation and low cost, and are typically made from high-density polyethylene and poly-vinyl- chloride. These plastic materials contain plasticisers, such as phthalate esters (PAEs), which help make the products softer and more flexible, but leach during the installed pipe life. The presence of phthalates in drinking water samples has been reported worldwide with levels ranging from 0.1 to 10 μg/L. It is increasingly important to understand their influence on the formation and resistance of biofilms within drinking water distribution systems as these biofilms are known to harbour pathogens such as Legionella, Pseudomonas aeruginosa, mycobacteria and others.
Wang and co-workers (a collaborative team from Hangzhou, China and Houston, Texas) have published “Phthalate Esters Released from Plastics Promote Biofilm Formation and Chlorine Resistance.” The authors investigated the behaviour of both Pseudomonas aeruginosa and multispecies biofilms following exposure to three different but commonly used plasticisers and the subsequent biofilm disinfectant resistance. The study found that biofilms exposed to plasticisers.
- produced more biofilm matrix, possibly as a defence mechanism
- biofilms produced were denser, and with increased biomass
- displayed increased bacteria quorum sensing/communication and gene-expression/transfer
- displayed increased antioxidative system expression which enhanced resistance to sodium hypochlorite disinfection.
Biofilms are widely acknowledged to be dominant contributors in human infection, therefore the creation of increasingly robust biofilms following stimulation by low levels of PAEs may make waterborne disease outbreaks more common, and potentially more difficult to treat. Given the scale of plastic pipe and plastic component installation within our drinking water systems, the significance of this research on public health cannot be underplayed.
Until we know more, should plastic pipework in healthcare buildings be risk assessed in a more serious light? How resilient and compatible are pipework materials over time and if exposed to continuous and/or shock chemical control measures? Do you know what materials containing plasticisers are installed in your water system? How would you advise your Water Safety Team if they were considering plastic pipes and components in their new build or refurbishment project? If you would like to talk more about these issues, or have other design and build questions, please contact Harper Water Management Group.
Wang H, Yu P, Schwarz C, Zhang B, Huo L, Shi B, Alvarez PJJ. Phthalate Esters Released from Plastics Promote Biofilm Formation and Chlorine Resistance. Environ Sci Technol. 2022 Jan 18;56(2):1081-1090. doi: 10.1021/acs.est.1c04857. Epub 2022 Jan 7. PMID: 34991317.
https://pubmed.ncbi.nlm.nih.gov/34991317/