A big thanks to  Mr Salty definitive proof there is hexavalent chromium in the

electrolyte solution, please be sure to dispose of this hazardous material properly

no one benefits from improper disposal.

 

Hexavalent chromium refers to chemical compounds that contain the element chromium in the +6 oxidation state. Hexavalent chromium is recognized as a human carcinogen via inhalation.Workers in many different occupations are exposed to hexavalent chromium. Problematic exposure is known to occur among workers who handle chromate-containing products as well as those who arc-weld stainless steel. Within the European Union, the use of hexavalent chromium in electronic equipment is largely prohibited by the Restriction of Hazardous Substances Directive. Hexavalent chromium is used for the production of stainless steel, textile dyes, wood preservation, leather tanning, and as anti-corrosion and conversion coatings as well as a variety of niche uses.

Toxicity

Hexavalent chromium compounds are genotoxic carcinogens. Chronic inhalation of hexavalent chromium compounds increases risk of lung cancer (lungs are especially vulnerable, followed by fine capillaries in kidneys and intestine). It appears that the mechanism of genotoxicity relies on pentavalent or trivalent chromium. According to some researchers, the damage is caused by hydroxyl radicals, produced during reoxidation of pentavalent chromium by hydrogen peroxide molecules present in the cell. Zinc chromate is the strongest carcinogen of the chromates used in industry. Soluble compounds, like chromic acid, are much weaker carcinogens.

In the U.S., the OSHA PEL for airborne exposures to hexavalent chromium is 5 µg/m³ (0.005 mg/m³).