A sudden increase in chromosome abnormalities in a mouse colony has raised questions about the safe level of exposure for bisphenol A, a chemical used to make some common plastics and resins.
In a research paper supported by the National Institute of Environmental Health Sciences, scientists at a genetics laboratory and an associated animal research center, both at Case Western Reserve University in Cleveland, describe the accident in the April 1 issue of the journal Current Biology :
The scientists found that the colony's semi-rigid plastic cages had deteriorated as the result of a handler's use of the wrong cleaner – a harsh detergent – which damaged the cages and led to the release of small amounts of the plasticizer bisphenol A, which is often abbreviated as BPA.
This low level exposure led to "highly significant" increases in abnormalities in the mice's developing eggs, called oocytes. These results were then confirmed in an experiment in which the animals' eggs were deliberately exposed, the scientists reported.
First author Patricia A. Hunt, Ph.D., of the Department of Genetics at Case Western Reserve said that the sudden increase in abnormalities appeared in a mouse colony used as a control group. "We suspected it might be caused by something environmental and so for several weeks we looked for an explanation – especially for any recent changes in the lab. Nothing turned up. But as I was heading out the door for some time off, I noticed that the plastic cages looked kind of the worst for wear. I thought maybe the autoclave" – a system producing pressurized steam to keep conditions sterile – "was causing the deterioration. I asked my co-workers to check on that. On my return, I was told that the autoclave didn't produce that effect on the plastic but that a temporary animal worker had mistakenly used a harsh, alkaline detergent on them.
"We then confirmed that such a detergent could break down the plastic caging and water bottles chemically, exposing the mice to bisphenol A at low levels."
The researchers then deliberately exposed mice to small amounts of bisphenol A. They found that, once again, their eggs showed greatly increased rates of two chromosome abnormalities. In normal mouse or human eggs, the chromosomes line up, ready for the egg to split in two when fertilized. But in many of the eggs of the exposed mice, the chromosomes were not aligned but disorganized. In addition, the egg cells of the exposed mice frequently had too few or too many chromosomes, a condition called aneuploidy.
These kinds of chromosomal abnormalities are the leading cause of miscarriage, congenital defects and mental retardation in humans.
Dr. Hunt said, "We don't know what the effects, if any, may be on humans at these low levels, but a study in Germany indicates pregnant women are exposed to similar levels of BPA, which is used in food and beverage containers. Certainly we should be concerned enough to carry out extensive further study."
Research on bisphenol A has stirred controversy for years. Generally, traditional testing – such as the 103-week rodent study carried out by the National Toxicology Program in 1982 – has not raised concerns, but several other studies have.
In 1997, research at the University of Missouri-Columbia suggested BPA has an estrogen-like activity. In these experiments, pregnant mice were exposed to low levels of bisphenol A at a time when their male fetuses' prostates were developing. The male offspring subsequently developed enlarged prostates at adulthood, the scientists reported in the NIEHS journal Environmental Health Perspectives.
Recently, the European Commission's Scientific Committee on Food lowered its Tolerable Daily Intake for bisphenol A five-fold.
Several years ago, EPA asked the National Toxicology Program to assemble a panel of academic, government and industry scientists to make recommendations on BPA and other environmental estrogens. In 2001, the panel said, among other things, that BPA might require special types of additional testing to assure that the levels permitted are safe.
The National Toxicology Program is headquartered at NIEHS in Research Triangle Park, N.C. NIEHS is one of the institutes of the National Institutes of Health, a part of the U.S. Department of Health and Human Services.
Some of the funding for the study came from a pool by the industry-supported American Chemistry Council. The Council, in 2001, agreed to provide $1 million to NIEHS for studies on human reproduction and fetal and childhood development. The Council has no role in selecting the studies, which are approved by the regular, independent peer review used by NIH.
OSHA TO DEVELOP INDUSTRY-SPECIFIC ERGONOMICS GUIDELINES FOR SHIPYARD INDUSTRY
OSHA will develop guidelines for the shipyard industry to help employers reduce ergonomic-related injuries among workers, Assistant Secretary of Labor for Occupational Safety and Health John L. Henshaw announced. Representatives from the industry and labor have agreed to work with OSHA to develop draft guidelines that will be available for public comment.
"We are continuing the process of working with stakeholders that want to reduce injuries and illnesses related to ergonomics," said Henshaw. "Several groups representing the shipyard industry, including the American Shipbuilding Association and the Shipbuilders Council of America, and labor groups, including the International Brotherhood of Boilermakers, Iron Ship Builders, Blacksmiths, Forgers and Helpers, AFL-CIO, and the International Brotherhood of Electrical Workers, AFL-CIO, have expressed their willingness to work with us to develop these guidelines."
Bureau of Labor Statistics data show that in 2001, the injury and illness rate for the shipyard industry was 17.2 compared to an injury and illness rate of 5.7 for all private industry. In 2001, 33.6 % of injuries and illnesses that resulted in days away from work for shipyard workers were musculoskeletal disorders (MSDs).
"The shipyard industry has already demonstrated its commitment to work with OSHA to reduce the numbers of overall injuries and illnesses suffered by workers in shipyards," continued Henshaw. "For example, in January 2003, the Shipbuilders Council of America signed an alliance with OSHA to work together to share our information and resources to reduce injuries and illness in shipyards. We are delighted to continue to expand OSHA's collaboration with the industry to develop ergonomic-related guidelines to capitalize and expand on the work the industry has already done."
The draft guidelines are expected to be ready for public comment later this year. They will be published in the Federal Register for review before becoming final.
OSHA announced its comprehensive plan to dramatically reduce ergonomic injuries on April 5, 2002. In addition to industry-and-task-specific guidelines, the plan includes tough enforcement measures, workplace outreach, advanced research, and dedicated efforts to protect Hispanic and other immigrant workers. The first set of industry-specific guidelines -for the nursing home industry - was published in final form on March 13, 2003.
ADVANCED NIOSH RESEARCH ON NEUROTOXICITY OPENS NEW AVENUES TOWARD PREVENTING JOB RISKS
Recent research findings by the National Institute for Occupational Safety and Health (NIOSH) point to new leads for studies that will help to protect individuals from the risk of nervous system impairments from work-related exposures to certain chemicals.
The findings also illustrate the practical application of new laboratory technologies for identifying and understanding subtle biochemical changes in the nervous system, at levels of analysis that would have been impossible a few years ago. Such changes may be very early precursors of serious impairments in the ability to think, move, or communicate. As such, they might lead to new and faster ways of recognizing hazards from occupational exposures in time to avert serious risks.
In recently published studies based on laboratory experiments and reviews of the latest scientific literature, NIOSH found that:
- Obesity may increase susceptibility to neurotoxic chemicals, based on comparisons between two groups of laboratory mice, an obese group and a lean group, that were exposed to two compounds. The comparisons focused on changes in certain cellular and biochemical features that are fundamentally similar to those of humans.
- Progressive weakness and other potential long-term effects associated with exposure to organophosphate chemicals, whether employed as nerve gas or in their more common usage as pesticides, may not begin with chemical changes in an enzyme known as "NTE," as scientists have widely believed. Based on new molecular data that throw conventional wisdom into question, certain other leads show more promise for better explaining the ways in which these effects may be initiated.
"The NIOSH findings do not provide final answers, nor are they intended to do so in this exploratory phase of the science, but they show that the questions are worth pursuing, and they provide new clues that can help scientists fill key gaps in current knowledge," said NIOSH Director John Howard, M.D. "For example, would the results found in the laboratory studies be the same in humans? If subtle changes may predict or lead eventually to clinical symptoms, how does that progression occur, what steps may be involved, and what does this suggest for early intervention and prevention?"
The NIOSH analysis was published in Nature Genetics (advance online publication), March 17, 2003. The NIOSH studies are part of a program of health effects laboratory research on neurotoxicity. In this program, NIOSH scientists are developing new "biomarkers" or ways to identify subtle cellular, molecular, and biochemical changes that may signal the potential onset of neurotoxic effects, and are applying those biomarkers to better understand how exposure to certain chemicals may lead to the development of symptoms. The application of this knowledge will lead to timely identification of neurotoxic agents, as well as development and implementation of early intervention and prevention strategies.
For further information about NIOSH research, or call the toll free NIOSH information number, 1-800-35-NIOSH (1-800-356-4674).
NORTH AMERICAN OFFICIALS MEET IN TEXAS AND MEXICO TO DISCUSS WORKPLACE SAFETY AND HEALTH PROGRAMS
Occupational safety and health officials from the United States, Mexico, and Canada have agreed on criteria to recognize excellence in workplace safety and health programs in all three nations. The group also reached consensus on key elements for establishing effective occupational safety and health management systems.
"Worker safety and health is a high priority for each of our nations and together we are addressing key issues and exchanging ideas in order to produce tangible results that will benefit all of our workers," said OSHA Administrator John Henshaw. "An important part of our joint efforts includes recognizing excellence in workplace safety and health programs and sharing that information with workers and employers throughout North America."
The officials, who serve on one of four subgroups of the Tri-national Occupational Safety and Health Working Group, met March 10-12 in Texas and Mexico, to discuss best practices, partnerships, voluntary programs, and occupational safety and health management systems.
