WHY ARE 96,000,000 BLACK BALLS
ON THIS
RESERVOIR?
46,816,008 views•May 10, 2019
VERITASIUM
7.17M subscribers
I took a boat through 96 million black
plastic balls on the Los Angeles reservoir to find out why they're there. The
first time I heard about shade balls the claim was they reduce evaporation. But
it turns out this isn't the reason they were introduced.
Huge thanks to LADWP for arranging this
special tour for me. Next time let's put the GoPro on the submersible!
The balls are made of high density
polyethylene (HDPE) which is less dense than water so they float on the surface
of the reservoir even if they break apart. They are 10cm (4 inches) in diameter
and contain about 210ml of water. So the main reason they are on the reservoir
is to block sunlight from entering the water and triggering a chemical reaction
that turns harmless bromide into carcinogenic bromate. This effect occurs with
prolonged exposure to bromate so regulators insist that levels be kept below 10
microgram per liter on average over a 12 month period.
Grateful thanks to VERITASIUM, all the people
in making this video and YouTube.
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