U.S. and Canadian factory workers who use laundered shop towels could be exposed to lead and other metals, according to a peer-reviewed study conducted by the environmental consulting firm Gradient.
Published in the October issue of Human and Ecological Risk Assessment, the study concludes that a worker using a typical number of laundered shop towels each day (14) could ingest an amount of lead that is 400 times higher than the health-based criterion for reproductive effects set by the California Environmental Protection Agency and more lead than that associated with federal EPA's action level for drinking water.
Workers cannot see, smell or feel heavy-metal residue on laundered shop towels, so the risk is not apparent to the many workers who use the towels to wipe parts, spills and their hands, the study notes.
"The study adds to the growing body of data on potential health risks associated with using laundered shop towels in the workplace," said Barbara Beck, principal at Cambridge, Mass.-based Gradient.
"We continue to find a range of heavy metals on commercially laundered towels. Of particular interest is that exposures to lead may exceed certain health-based limits. Much as bacteria and viruses can spread through touch and be ingested, heavy metals on shop towels may also be transferred through touch to workers' mouths and be swallowed."
In addition to the potential for exposure to unhealthy levels of lead, workers using laundered shop towels also may be exposed to aluminum, cadmium, cobalt, copper and iron at levels exceeding intakes associated with drinking water standards set by EPA and other toxicity criteria, the study found.
Workers with high-end exposures could be exposed to lead at levels up to 1,170 times higher than the CalEPA criterion for reproductive effects and 19.5 times more than the amount associated with the EPA action level for lead in drinking water.
In the study, exposure to metals by workers using laundered shop towels was estimated based on metal concentrations in towels and exposure modeling. The resulting exposure estimates were screened against recognized toxicity or regulatory criteria, according to Gradient.
Gradient estimated worker exposure levels for the towels tested based on current data regarding transfer of residues to hands, the number of towels workers used daily and an approximation of the percent of towel surface area that came into contact with the hand. Transfer models enabled Gradient to estimate the movement of metals from towels to hands and then the mouth.
Additionally, scanning electron microscope imaging demonstrated the presence of heavy metal particles on the surface of the laundered shop towels; the particles were too small to be seen with the naked eye.
The study, funded by Kimberly-Clark Corp., estimated worker exposure to 28 different metals in laundered towels collected from 38 U.S. and 16 Canadian companies, including printing, aviation, automotive, metal manufacturing, electronics, food and beverage packaging, chemical manufacturing and a range of other industries, as well as military plants.
"This study builds on a 2003 Gradient analysis showing that shop towels retain measurable levels of metals after commercial laundering and extends the findings presented in 2012 at the annual Society of Toxicology conference," the firm said in a news release.