Plastic pipes exposed to high drinking water temperatures can filter out hazardous chemicals

In August, a huge forest fire devastated the San Lorenzo Valley north of Santa Cruz, California, destroying nearly 1,500 buildings and exposing many others to extreme heat. Before the fire was put out, laboratory tests revealed benzene levels of up to 9.1 parts per billion in residential water samples, nine times the state’s maximum level of safety.

This is not the first time carcinogens have followed forest fires: California water managers have found unsafe levels of benzene and other volatile organic compounds or VOCs in Santa Rosa after the 2017 Tubbs fire and in Paradise after the 2018 campfire.

Scientists suspected that, among other possibilities, plastic drinking water pipes exposed to extreme heat released chemicals (SN: 13/11/20). Now laboratory experiments show that it is possible.

Andrew Whelton, an environmental engineer at Purdue University in West Lafayette, Indiana, and his colleagues subjected commonly available pipes to temperatures of 200 ° C to 400 ° C. These temperatures, hot enough to damage the pipes, can occur as heat radiates. of nearby flames, Whelton says.

A plastic water pipe (left) and a meter box (right) were found from homes in Paradise, California, after a community fire burned in 2018, revealing the extent to which plastic can melt when exposed to high temperatures.Andrew Whelton / Purdue University (CC-BY-ND)

When researchers submerged the pipes in water and cooled them, different amounts of benzene and VOCs – more than 100 chemicals in some tests – leaked from 10 of the 11 types of pipes into the water, the team reported in the December 14 issue of Environmental Science: Research and water technology.

“Some of the contamination from past fires probably came from thermally damaged plastic,” Whelton says. It is impossible to conduct experiments in the middle of a raging fire to determine the exact source of the pollution, he says, but an inspection of damaged pipes after the fact may indicate the temperature they may experience.

Benzene exposure can cause immediate health problems, such as skin and throat irritation, dizziness, and long-term consequences such as leukemia. The team suggests testing drinking water if a fire approaches your property and, if possible, replacing any plastic in the home’s plumbing system with heat-resistant metal.

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