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

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

This isn’t the first time the carcinogen has been following forest fires: California water managers found unsafe levels of benzene and other volatile organic compounds or VOCs in Santa Rosa after the Tubbs Fire in 2017 and in Paradise after the Camp Fire in 2018 .

Scientists suspected that, among other possibilities, plastic pipes of drinking water 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 colleagues subjected commonly available pipes to temperatures of 200 ° C to 400 ° C. Those temperatures, hot enough to damage but not destroy the pipes, can occur as the heat radiates. of nearby flames, says Whelton.

A plastic water pipe (left) and a meter box (right) recovered from homes in Paradise, California, after the blaze burned the community in 2018 reveal the degree to which plastics can melt when they expose to high temperatures.Andrew Whelton / Purdue University (CC-BY-ND)

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

“Some contamination from past fires has probably originated from thermally damaged plastics,” Whelton says. It is impossible to conduct experiments in the midst of a raging fire to pinpoint the exact source of the contamination, he says, but inspecting damaged pipes after the fact may suggest what temperatures they may experience.

Exposure to benzene can cause immediate health problems, such as skin and throat irritation, dizziness, and long-term effects such as leukemia. The team suggests testing drinking water if the fire gets close to your property and, if possible, replacing any plastic in a home’s water system with heat-resistant metal.

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