Chemical Analysis of Organic Compounds in Footwear

In view of that chemical emission from point sources such as industries has decreased over the years; chemical emission from articles has been pointed out to be of increasing concern. Hence, it is important to get a better understanding of the chemical content in different types of articles. The aim of this study was to provide information regarding the organic chemical content in footwear by chemical analysis of materials sampled from three shoes from well known brands (Ecco, Nike and Vagabond). Materials from the outsole, midsole, upper and the lining were extracted by methanol and analysed with GC-MS and HPLC-MS/MS. Overall, 31 compounds were identified at levels of parts per million in the sampled materials. Both plasticizers, antioxidants, solvents, vulcanization agents, surfactants, flame retardants, oxidants and biocides were found. Among the compounds identified, 11 high production volume chemicals and six compounds classified as either toxic to aquatic organisms, carcinogenic or toxic for reproduction were found. Three of these compounds (diisobutyl phthalate, dibutyl phthalate and bis(2-etyhylhexyl)phthalate) are included on the candidate list for authorization within REACH. However, the levels were approximately 100-1000 times lower than the limit stated in the European chemical regulation (REACH), for which requirements are put on manufacturers and importers. As an attempt to model weathering and leaching in the environment, outsole material from each shoe was subjected to soaking extraction using synthetic brackish water. The water samples obtained were found to contain only a few organic chemicals at levels of parts per million. The number of compounds was less compared to when outsole material was extracted using methanol. Hence, not all organic compounds identified in the three outsoles seem to have potential to be released under environmental conditions through leaching. The water samples were also used to evaluate the toxicity of footwear outsoles. The toxicity tests were carried out at the Department of Applied Environmental Science (ITM) by Ellen Kahn as a part of her diploma work. Both larval development test and growth inhibition tests were performed using Nitocra spinipes and Ceramium tenuicorne. The toxic effects observed by Ellen Kahn could not be explained by the levels of organic compounds identified in the water samples. Instead inorganic compounds (e.g zinc) were pointed out as the probable cause. Even though the levels of organic chemicals identified in this study were found to be low, the great number of different chemicals identified in the sampled materials raises the question about the widespread use of chemicals in articles.

Subscribe to our newsletter