The claim that plastic shade balls used in the LA reservoir leach chemicals into drinking water can be denied based on the following points.
- The shade balls are coated in carbon black, a food-safe pigment with an albedo near zero. Any sunlight that is absorbed by the ball is not reflected or refracted since its basically dark. Dark colors absorb light and heat up faster than lighter colors that reflect light and the primary goal of these shade balls is to prevent light from reaching the water.
A spokesperson from the ball-manufacturing company XavierC explains that this theory is backed up by their testing, “After decades of testing, black has been deemed the color that provides the best protection.”
- Carbon black is nearly-pure elemental carbon produced by burning hydrocarbons in an air-poor environment used worldwide in food packaging.
It is used worldwide in food packaging, and meets the NSF/ANSI 61 standards for materials that come in contact with drinking water.
As a matter of fact, the same plastic is used for water pipes worldwide. The shade ball material and production process have been certified by National Sanitation Foundation (NSF) International. The balls comply with federal standards and are considered safe to be in contact with drinking water.
- Carbon black will prevent the plastic from breaking down in UV light, which also help the balls survive longer and give them a multi-decade lifespan.
Sydney Chase, president of XavierC, one of the shade ball supply companies behind the project, said the color is a result of pure black carbon being added to the high density polyethylene plastic to take in ultra-violet rays and subsequently stop sunlight from penetrating the plastic. Any other color would have required dyes, said Rodriguez, which could have then leached into the water while the carbon black does not.
- Department of Water and Power (DWP) confirms that this is safe and the 4-inch-diameter balls are made from high-density polyethylene, which is the same material found in a one-gallon milk jug. This plastic is approved to come into contact with drinking water.
The balls do not emit any chemicals, according to the DWP. They should last 10 years. At some point, they will lose their structural integrity and could split at the seams.
- It is not the first time Los Angeles utilized the concept. Shade balls were placed on Ivanhoe Reservoir in September 2008, Elysian Reservoir in February 2009 and Upper Stone Canyon Reservoir in April 2012 to protect their water quality and prevent evaporation.
At Elysian, Ivanhoe and Upper Stone Canyon Reservoirs, the shade balls are temporary. At Ivanhoe, the shade balls will be removed when Headworks Reservoir East is complete and fully operational. Shade balls on Elysian and Upper Stone Canyon Reservoirs will be removed as floating covers are installed. At Los Angeles Reservoir, the shade ball solution is permanent. They will be removed, recycled and replaced every 10 years.
- There is no evidence that shade balls have degraded into "micro-plastics.” since this method was initiated in 2008.
Since initiating this method in 2008, LADWP has seen no evidence that shade balls have degraded into "micro-plastics.” Reservoir water is sampled extensively throughout the system and no plastic pieces or chemical leaching from the shade balls have been detected.
- LADWP uses the same plastic for water pipes which is authorized for safe usage by the appropriate nationally recognized authorities. Furthermore, LADWP has tested the water for several known endocrine disruptor compounds and chemicals, and none were detected in the results.
LADWP worked with the manufacturers to consider other colors including blue. However, the lack of UV stabilizers and inhibitors in the color resins that were tested did not hold up well to sunlight and the balls would have degraded within one to five years. Other colors would not totally block UV light and would have required dyes, which do leach into the water. The carbon black does not emit or leach any chemicals.
- Shade balls method has complied with several governmental water quality regulations.
For Los Angeles Reservoir, shade balls in concert with UV treatment and operational modifications to the water distribution system will allow LADWP to comply with state and federal water quality regulations from the California Department of Drinking Water (DDW) and the United States Environmental Protection Agency (US EPA). These regulations include the Safe Drinking Water Act, US EPA’s Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBP Rule).
Some of the above points are referred from the source here and research also shows that no technique exists that can detect all toxic substances in extracts.