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.


Phthalate esters (PAEs) are commonly released from plastic pipes in some water distribution systems. Here, we show that exposure to a low concentration (1-10 μg/L) of three PAEs (dimethyl phthalate (DMP), di-n-hexyl phthalate (DnHP), and di-(2-ethylhexyl) phthalate (DEHP)) promotes Pseudomonas biofilm formation and resistance to free chlorine. At PAE concentrations ranging from 1 to 5 μg/L, genes coding for quorum sensing, extracellular polymeric substances excretion, and oxidative stress resistance were upregulated by 2.7- to 16.8-fold, 2.1- to 18.9-fold, and 1.6- to 9.9-fold, respectively. Accordingly, more biofilm matrix was produced and the polysaccharide and eDNA contents increased by 30.3-82.3 and 10.3-39.3%, respectively, relative to the unexposed controls. Confocal laser scanning microscopy showed that PAE exposure stimulated biofilm densification (volumetric fraction increased from 27.1 to 38.0-50.6%), which would hinder disinfectant diffusion. Biofilm densification was verified by atomic force microscopy, which measured an increase of elastic modulus by 2.0- to 3.2-fold. PAE exposure also stimulated the antioxidative system, with cell-normalized superoxide dismutase, catalase, and glutathione activities increasing by 1.8- to 3.0-fold, 1.0- to 2.0-fold, and 1.2- to 1.6-fold, respectively. This likely protected cells against oxidative damage by chlorine. Overall, we demonstrate that biofilm exposure to environmentally relevant levels of PAEs can upregulate molecular processes and physiologic changes that promote biofilm densification and antioxidative system expression, which enhance biofilm resistance to disinfectants.

Keywords: biofilm densification; disinfectant resistance; oxidative stress; phthalate esters.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biofilms
  • China
  • Chlorine / pharmacology
  • Dibutyl Phthalate
  • Diethylhexyl Phthalate*
  • Esters
  • Phthalic Acids* / pharmacology
  • Plastics


  • Esters
  • Phthalic Acids
  • Plastics
  • Dibutyl Phthalate
  • Chlorine
  • phthalic acid
  • Diethylhexyl Phthalate