As drinking water flows through pipes, it sometimes comes into contact with the rubber seals inside various plumbing devices. These parts contain additives that contribute to their flexibility and durability, but which are also potentially harmful compounds that can leak into drinking water.
Previous research on the impact of rubber on human health tended to focus on tyres and the microparticles produced during their use.
But a new small-scale study, published in Environmental Science & Technology Letters, found that the compounds released into water from plumbing infrastructure sometimes transformed into unwanted byproducts.
To enhance rubber's strength and durability, manufacturers typically mix in additives. Previous research from the same team showed that these can react with disinfectants in simulated drinking water. Their lab tests generated a variety of chlorinated compounds, some of which could damage DNA.
This time, the team wanted to assess whether real-world rubber plumbing fixtures could release compounds known as DPG and 6PPD and form chlorinated byproducts in drinking water samples.
In the pilot study, the team collected tap water from 20 buildings and detected polymer additives at parts per trillion levels in every sample.
The researchers explain that these compounds are not currently regulated, but the measured levels are potentially concerning, based on their previous study's results from human cell bioassays.
The samples from faucets with aerators contained the highest amounts. All the samples contained DPG and one of its chlorinated byproducts, whereas 6PPD and two other chlorine-containing compounds were each found in fewer than five samples.
To see if these compounds could have come from plumbing fixtures, the team tested rubber O-rings and gaskets from seven commercial devices, including faucet aerators and connection seals.
In the experiment, the rings sat in water with or without chlorinated disinfectants for up to two weeks. Most of the seals, except for the silicone-based ones, released DPG and 6PPD additives.
Additionally, plumbing pieces sitting in disinfectant-treated water generated chlorinated forms of DPG in amounts that were consistent with those observed in the drinking water samples. Because some of the rubber plumbing seals released DPG and 6PPD, the researchers say that drinking water, as well as tyre pollution, could be a route for these compounds towards human exposure.
