New Workplace Environmental Exposure Level (WEEL) values for octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) are now available. The two WEELs appear in the January issue of .

According to the WEEL documentation, D4 is used as a monomer in the manufacture of polymeric materials, which are widely used in various industrial and consumer applications, topical pharmaceutical formulations, and as breast implants. The recommended WEEL value for D4 is 10 ppm as an 8-hour time-weighted average (TWA).

The WEEL documentation for D5 notes that it is used in dry cleaning, electronics, and lubricants, and as a carrier ingredient in many toiletries and cosmetics. The chemical is also a precursor in the production of siloxane polymers for industry and medicine. The recommended WEEL value for D5 is 10 ppm (8-hour TWA).

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