More than 20 Los Angeles lifeguards developed rashes and bacterial infections last month after swimming in a manmade lake after warning city officials that conditions were unsafe, and have filed a grievance with the city.

Jasper Kim, a lifeguard for 13 years, said he and other lifeguards were required to perform a water skills test at Hansen Dam Aquatic Center in northeast Los Angeles.

He said he told his supervisors before the exam that the water hadn’t been tested for parasites and wasn’t safe. But the supervisors didn’t listen, according to the grievance.

Hansen Dam Aquatic Center is a manmade freshwater lake in northeast Los Angeles. (laparks.org)

22 of the 64 lifeguards who took the exam developed respiratory issues and skin rashes and needed medical attention, the Los Angeles Times reported. The rashes, known as “swimmer’s itch,” is an allergic reaction to parasites released by snails in fresh and salt water.

The Los Angeles Department of Recreation and Parks said they tested the water before the exam and found no evidence of parasites, the Times reported.

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Kim, who is the named lifeguard in the grievance, said his supervisors wouldn’t allow him to use sick days or take a vacation “despite this troubling medical condition.”

The grievance calls upon the parks departments to test the public open waters and restore employees lost wages and benefits.

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In a statement, the parks department said it “seeks the highest quality conditions to ensure the public’s safety and will continue to work with the affected employees to ensure they receive any care or work assistance.”