We’re talking about California, whose voters initially passed Proposition 65 – commonly called Prop 65 – back in 1986 as the Safe Drinking Water and Toxic Enforcement Act. The intention was to ensure citizens have information about the chemicals in products, foods and the environment so they can make informed decisions.

The act requires businesses to notify Californians about significant amounts of potentially toxic chemicals in the products they purchase, in their homes or workplaces, or that are released into the environment. The result is a list of chemicals, both synthetic and natural, that are known to cause cancer, birth defects or other reproductive harm. Updated annually, the list has ballooned to around 900 substances, including hexavalent chromium – or chrome VI – which was added to the list in 2008. Products that expose consumers to significant amounts of the listed chemicals must carry a warning label.

Tanneries use chrome III in tanning, never chrome VI. In fact, in June 2019, Cotance secretarygeneral Gustavo Gonzalez-Quijano wrote in Leather International that there is nothing to fear from chromium. He emphasises that appropriate technologies and reputable chemicals, as well as quality control, provide a high level of safety.

This is key because in Europe, since 2015, EU law requires tanneries to restrict the presence of chrome VI in all leather articles that may come into contact with the skin under Registration, Evaluation, Authorisation and Restriction of Michael Vi/Shutterstock.com Chemicals (REACH) regulation. What has not occurred in Europe is the widespread use of warning labels or the prevalence of lawsuits as in California.

Why leather now?

 Obviously, chrome VI toxicity is not new, but groups in the state have started testing unlabelled products and pursuing litigation against the relevant manufacturers and retailers. This is how leather gloves and shoes landed in the crosshair of Prop 65 lawsuits.

“The results of current litigation will apply to any consumer good that contains leather,” says Stephen Sothmann, president of the Leather & Hide Council of America (LHCA). While the focus is gloves and shoes, it’s only a matter of time before upholstery and bags are included, he adds. The LHCA is not a defendant in the litigation but is supporting the defence argument on behalf of shoe and glove companies being sued in the state.

 Currently, plaintiffs are only required to show that they found the chemical in a product and then the burden of proof shifts to the manufacturer. That company must then prove that the chemical in question is below the minimum allowable quantity. For chrome VI, that is three parts per million (ppm).

From safeguard to questionable

In California – or on products sold to consumers in California – Prop 65 warning labels are everywhere. It’s almost impossible to shop online without encountering the warning, slapped on goods of all kinds. As Michael Waters wrote in Vox a few years ago, Prop 65’s authors envisaged the law as a “radical way to hold companies accountable for their product”.

 Now however, a small group of private enforcers have turned Prop 65 litigation into a big business. Waters says that “some of the most successful private enforcers are law firms that make use of a provision in Prop 65 allowing California residents to file actions against companies for the public good”.

 Here’s an example. In a 2021 story entitled ‘No, this Supreme jacket won’t give you cancer’, Online magazine Highsnobiety pointed out that the brand’s latest leather coat carries a Prop 65 warning. “Have no fear – the only thing to fear is far-reaching legislation,” the author writes. He also notes that the good intentions behind the proposition have morphed into something else entirely and that these days, “it’s better known for marking Starbucks coffee as potentially life-threatening”.

 “Every dry cleaner, every restaurant you walk in has a Prop 65 warning in the window,” Tom Houston told Vox. Houston helped draft the initial bill when he was chief deputy to Tom Bradley who was the mayor of Los Angeles at the time.

 “Everybody just ignores that. The major purposes have all been established. The major bad chemicals


are off the market, the major bad actors have been corralled by the initiative. Now this is getting to be almost ridiculous.

Resolution options

 To date, businesses have had few options for resolving lawsuits. “Companies can agree to add a warning label to products and pay a fine, and many have chosen to do so,” Sothmann says. Others don’t believe this is fair and opt to fight it, maintaining that the nature of the goods and the likelihood of chrome VI leaching into the body is minimal, he explains.

"The results of current litigation will apply to any consumer good that contains leather"
Stephen Sothmann, president, Leather & Hide Council of America

Chrome VI is, in fact, naturally occurring and the human body metabolises it. As long as levels are not toxic, it is not a problem. What is problematic is that current litigation focuses on the content level of chrome VI while Prop 65 is intended to target exposure.

The changeable nature of chrome VI

 Accurately measuring chrome VI in leather is a difficult issue in and of itself. Under specific conditions, trivalent chromium – chromium III – can convert to chrome VI. This means that leather can leave a tannery in perfect condition but improper storage of the leather or the final goods could lead to the creation of chrome VI. Complicating matters further, chrome VI can transform back into chrome III.

 “Chrome III has potential for oxidation, which converts it to chrome VI,” says Steve Lange, director of the Leather Research Laboratory at the University of Cincinnati. “High heat and perhaps UV exposure can cause the conversion, although there seems to be a higher correlation with heat,” Lange explains.

 The International Union of Leather Technologists and Chemists Societies (IULTC) has published guidelines on preventing chrome VI creation that tanneries can use. Also, some processes such as vegetable retanning can help prevent it from happening and in some cases can mitigate the creation of chrome VI.

 Another major issue underlying the current California litigation is the testing process itself.

“Leather presents a very challenging sampling matrix and that limits the detection limit of the test method to 3ppm.” Lange explains. “The recent introduction of the ion chromatography test method reduced the possibility of false positives but the detection limit is still only 3ppm.”

 Threats to chrome tanning

Since 2019, dozens of lawsuits under Prop 65 have targeted chrome VI in leather articles, so far mostly gloves and to a lesser extent shoes. Some companies have decided to settle, but if these types of lawsuits expand, it could be a threat to chrome tanning on a global scale. If you’re wondering why one US state out of 50 can make such a big difference, keep in mind that if California were a country, it would be the world’s fifth largest economy. In fact, it’s big enough that it could soon knock Germany out of the number four spot, according to Bloomberg.

 Many of the settlements simply require products to have warning labels and companies to pay a fine, but one recent case requires that any footwear distributed by the offending group contain chromefree leather – a first for a Prop 65 settlement.

“Chrome III has potential for oxidation, which converts it to chrome VI. High heat and perhaps UV exposure can cause the conversion, although there seems to be a higher correlation with heat.” Steve Lange, Leather Research Lab, University of Cincinnati

In this case, “chrome-free leather” means that it was “not at any point in the production process treated or tanned with chromium based tannins, including but not limited to chromium sulphate; (b) was not otherwise treated, dyed or exposed to chemicals that contain chromium as an intended ingredient; and (c) was not produced in tanneries that have material residual chromium contamination; and (d) has extractable chromium of less than two part per million by weight when tested pursuant to ISO 17072-1 or a successor ISO standard that measures extractable total chromium”.

“The effects of the current litigation would mean that any tannery making leather for goods being sold into California would have to comply with a warning label,” Sothmann says. It would come down to either labelling the goods or not using leather.

 Litigation is moving forward, but questions overshadow the process. The industry at large will want to keep an eye on the outcome and what it could gabriel12/Shutterstock.com mean for the future of chrome-tanned leather goods.

How chemicals are added to the Proposition 65 list

There are four ways for a chemical to be added to the Proposition 65 list.

  1. Labor Code (LC)

Chemicals are added to the list if they are identified by the World Health Organisation’s International Agency for Research on Cancer (IARC) as causing cancer in humans or laboratory animals. Proposition 65 says the list “at a minimum” shall consist of chemicals recognised as carcinogens in the California Labor Code, which in turn recognises carcinogens identified by IARC.


  1. State’s Qualified Experts (SQE)

Either of two independent committees of expert scientists and health professionals can find that a chemical has been clearly shown to cause cancer or birth defects or other reproductive harm. These two committees – the Carcinogen Identification Committee (CIC) and the Developmental and Reproductive Toxicant Identification Committee (DARTIC) – meet at least once each year and are designated as the “State’s Qualified Experts” for evaluation of chemicals under Proposition 65.


  1. Authoritative Bodies (AB)

The CIC and DARTIC have designated certain organisations as “authoritative bodies.” A chemical will be added to the Proposition 65 list if one of these authoritative bodies formally identifies it as causing cancer or birth defects or other reproductive harm. The following organisations have been designated as authoritative bodies: the US Environmental Protection Agency, US Food and Drug Administration (US FDA), National Institute for Occupational Safety and Health, the National Toxicology Program of the US Department of Health and Human Services and the World Health Organisation’s International Agency for Research on Cancer (IARC).

  1. Formally Required to be Labelled (FR)

If an agency of the state or federal government requires that a chemical be labelled or identified as causing cancer or birth defects or other reproductive harm, it will be added to the list. Most chemicals listed in this manner are prescription drugs that are required by the US FDA to contain warnings relating to cancer or birth defects or other reproductive harm.