New findings on lead particles mean lower absorption rates

A study sponsored by Battery Council International has found that the lead particles in that air at lead battery manufacturing facilities are larger than has previously been assumed, which means absorption rates in workers could have been dramatically over-estimated, BCI announced on August 28.

The study, published in the peer-reviewed Journal of Occupational and Environmental Hygiene, which focuses on workplace conditions and safety, claims to be the first modern study to analyze actual workplace lead-in-air data collected in the US.

“It finds that the lead in air at lead battery manufacturing facilities and secondary smelter facilities has a larger particle size than was previously assumed, which could dramatically reduce the rate at which workers absorb lead into the body,” says the announcement.

“The study posits that this means that prior modelling efforts likely over-estimate the rate at which airborne lead would be absorbed by workers’ bodies.”

Tests were carried out at nine manufacturing facilities and five secondary smelters across the US, with average mass median aerodynamic diameters ranging from 21µm to 32µm at the manufacturers and from 15µm to 25µm at the smelters.

Data concluded that the presence of submicron range lead mass measured at these facilities was generally small, from 0.8%-3.3% at manufacturing facilities and 0.44%-6.1% at smelters.

Mark Thorsby, executive vice-president of BCI, said the findings confirmed the position that BCI had taken for years — that it should be the blood levels of workers that are taken into account and not the air lead levels inside facilities.

“As the results of the study affirm BCI’s position, we believe they will advance everyone’s understanding of the science of worker safety,” he told BESB.

Although Thorsby said it was unlikely that any changes would be made in legislation immediately following this report, he said he hoped more attention would now be focused on lead in blood, not air.

The study, which was commissioned in 2013, has been meticulously peer reviewed, which is why the findings have taken so long to be published, said David Weinberg, who is a legal adviser to BCI.

“Once the preliminary results came in, BCI recognized the importance of the data set and brought in independent consultancy Gradient to further analyze the complete data set,” he told BESB. “Gradient drafted the manuscript that eventually became the article published.

“Given the ground-breaking nature of the data, Gradient first sought a peer review of the draft manuscript from a leading academic, and then submitted the paper to the well respected peer-reviewed journal in which it was published. The journal also sought a peer review. These reviews just take time.”

The timeframe in which the article was published was in line with similarly peer-reviewed articles, Weinberg said.

“BCI believed it was important to ensure the published results were iron-clad,” he said. “By contrast, the California OEHHA “Leggett Plus” model has never been published in a peer-reviewed journal.”

In another positive message to the lead battery industry, The Sustainability Consortium, a US organization that aims to make consumer products more sustainable, named lead batteries as one of the top five sustainable consumer products along with household paper products, leafy vegetables, computers and diapers.

In its July report, entitled The Call for Collective Action Across Supply Chains, TSC said these were the only five products that scored more than 64 (with the top score being 100) in sustainability.

“Lead batteries are critical for many green technologies, such as hybrid and electric vehicles, and to store and optimize renewable energy. They are truly an essential, innovative and sustainable product that powers and protects our way of life,” said the report.