Leather shoes spread environmental toxicants
When we use ordinary leather shoes, there is a risk that various kinds of environmental toxicants cross the skin and enter our bodies or leach out of the waste shoes in landfills into soil and groundwater. These are the results of an investigation into the content of shoes conducted by the Swedish Society for Nature Conservation as part of its initiative to identify environmental toxicants in everyday consumer products. Towels, t-shirts, sun protection products and plastic shoes are other products that have been analysed by the Swedish Society for Nature Conservation (SSNC) to date.
The analysis of leather shoes was conducted as a partnership between the SSNC and environmental organisations in South Africa, Uganda, the Philippines, India and Belarus. Altogether the organisations bought twenty-one pairs of well-known brand shoes in their various countries. These were analysed for a number of metals and organic compounds. Most of the chemical compounds studied can be assumed to originate from the tanning, preservation or dyeing of the leather.
Toxicants cross borders in goods
Shoes are one example of the many goods that are manufactured in several different countries, exported and imported. Environmentally hazardous toxicants that are banned from a country may nevertheless enter that country in a pair of shoes and find their way into the environment and human bodies. Existing chemical substances legislation often means that the control and monitoring of toxicants in imported goods are inadequate or non-existent.
The leather industry produces large volumes of wastewater, rich in organic compounds that consume oxygen upon degradation, as well as salt and various other chemicals. It also generates solid waste in the form of contaminated sewage sludge and leather waste.
Some of the tanning chemicals remain in the leather as it is further processed into various consumer goods, such as shoes. A shoe is a complex product that is assembled from many different materials, requiring a number of different chemicals in the making. Finally, when the shoe reaches the consumer, it contains a cocktail of chemicals.
Metals in various concentrations were found in all the shoes that were analysed. Although there may be no immediate risk to the wearer of the shoes, they may pose a long-term health risk to humans and the environment as shoes end up as waste and the metals and semi-metals they contain will eventually leach out and enter the natural environment.
Extremely high levels of trivalent chromium were found in the shoes. Chromium tanning accounts for some 80-85% of all tanning globally. When leather shoes and waste are incinerated or dumped in landfills, the most common and least toxic form of chromium, trivalent chromium, may oxidise into the highly toxic and carcinogenic hexavalent form.
Highly toxic metals, such as arsenic, lead and mercury, were also found in some shoes at concentrations higher than the levels found in untanned raw hide. In the form of organic compounds, arsenic and mercury can be used as leather preservatives. The organic forms of these elements are more easily assimilated from the shoes by the wearer. In this study, however, it was not possible to deduce in what forms arsenic and mercury were present in the leather. The contents of all shoes (except for one pair) purchased in Sweden may be in violation of Sweden's ban on mercury.