Main Uses and Environmental Emissions of Volatile Methylsiloxanes

The main uses and environmental emissions of cyclic methylsiloxanes (CMSs) and linear methylsiloxanes (LMSs), especially the three volatile CMSs (D4, D5, and D6), were reviewed. This chapter provides information on production, use, concentrations in various products, as well as emission of volatile methylsiloxanes (VMSs) into the environment. Many silicone-based products contain residues of CMSs as impurities, and hence the occurrence of VMSs in silicone-based materials (such as rubber products) has been described. CMSs are mainly used as intermediates in the production of silicone polymers, silicone fluids, elastomers, and resins, all of which have diverse industrial and consumer applications. CMSs are also used directly in personal care products (PCPs), as carriers. The concentrations and profiles of CMSs and LMSs in PCPs and household products from North America, Europe, and Asia varied widely across and within the product categories. The measured concentrations ranged from 0.01% in body wash to 70% (by weight) in deodorants. D5 was the predominant CMS found with high detection frequency in most PCPs. The correlations among VMSs in consumer products suggested incorporation of different blends of silicones to the raw material or as additives in those products. The industrial production of VMSs and direct use of PCPs result in significant emissions of VMSs into the environment. High production volume, high mobility, and environmental persistence of VMSs are causes of concern. VMSs, especially CMSs, were found globally in various environmental matrices including air, water, and sludge. This chapter also provides information on the concentrations and patterns of VMSs in the environment surrounding silicone factories, paper production facilities, and oil fields.