Testing method: XRF (x-ray fluorescent) tests for heavy metals.
Findings: Many of the tennis balls produced for the pet industry only obtained a "moderate level" rating. The few that did get a "low level" rating still had levels of lead, tin, chromium and or other heavy metals. Penn & Wilson tennis balls attained a "none level" rating with zero harmful chemicals.
Facts: Approximately 300 million tennis balls are produced each year, contributing roughly 20,000 tons of rubber to the landfills. This does not include the balls produced just for the pet industry.