A new federal rule aimed at protecting an estimated 2.3 million workers in the US from silica exposure could affect the plastics and compounding industries. The legislation is set to take effect on Jun. 23, although the first compliance dates are at least another year away: Jun. 23, 2017 for construction; Jun. 23, 2018 for general industry which would include plastics manufacturing; and Jun. 23, 2021 for oil and gas fracking.

The rules would cut the exposure limit for silica dust in the construction industry to 50 micrograms per cubic meter of air. The previous levels, set in 1971, allowed 250 micrograms in construction and 100 micrograms in other industries.

As well as mining and construction, precipitated and fumed silica are used in plastics as fillers, thickeners or softeners and in aiding flow for processing thermoplastics, compounds, composites and thermoplastic elastomers. Silica can also replace plastic microbeads in cosmetics and personal care products.

The Occupational Safety and Health Administration (OSHA) estimates the cost of the rule at about $1 billion annually with net benefits of $7.7 billion a year once the rule has taken effect.

However, trade groups, including the American Chemistry Council (ACC), believe the costs would be much higher. A study on behalf of ACC predicts the incremental costs of meeting the new standards would be around $4.7 billion per year and says a more economical solution would be to better enforce the original rules.

OSHA concurs that as many as 30% of US companies exposing workers to silica dust are not complying with the existing standards. Petitions challenging the new rules have been filed in six federal appeals courts, although the Labor Department has asked the courts to consolidate them into a single case.