DWP drops 400,000 balls onto Ivanhoe Reservoir - Los Angeles Times

This is pretty cool. According tothis article in the LA Times, the LA DPW has just dumped 40,000 black plastic balls into the Ivanhoe reservoir. The reason? To protect the water from the sun. Apparently, there's a fair amount of bromine in the local water filling the reservoir. In the presence of sunlight, and the chlorine added to keep things potable, bromate can form. Long term consumption of bromate can lead to cancer. So, they blot out the sun with (eventually) 3 million balls, until they can construct a more permanent cover.

Now, the big question. In light of recent reports about plastics leaching into warm water, and given that black plastic balls will inevitably get hot in the summer sun, has Los Angeles just traded one carcinogen for another?

Web Research Update: The article says they're using airport "bird balls". If they're the same as those made by this manufacturer, they're made of high-density poly-ethylene (HDPE). And, good news! According to this page from the Sierra Club, HDPE is not know to leach harmful chemicals. Well. Apparently, the LA DPW knows what they're doing. Very good. Please continue with your Public Works.