Chrysotile situation in the United States today

Chrysotile is a valuable raw material in the United States today for production of vehicle braking systems, asphaltic roof coatings and gaskets. The U.S. consumes about 13,000 metric tonnes of chrysotile per year. And, chrysotile cement pipe and sheets are imported for use. Amphiboles asbestos are no longer used for friable insulation or similar products that caused high worker exposures many decades ago.

Although use of chrysotile is stringently regulated in the United States to assure that workers and consumers are not significantly exposed to fibers, only one restriction exists on the types of products that can be manufactured with chrysotile. Product manufacturers are free to market any asbestos containing product that was being marketed in 1989; EPA approval must be obtained before marketing any new asbestos-containing product not being produced in 1989.

In the mid-1980's, public panic over asbestos in buildings - which was later discovered to have been unwarranted - prompted the U.S. Environmental Protection Agency (EPA) to propose a ban on all asbestos-containing products. EPA's proposal resulted in a massive compilation of information on the benefits of asbestos in many products, as well as the potential risk for human exposure in such uses. Based on this comprehensive record, the U.S. Court of Appeals for the Fifth Circuit found such a ban unwarranted. Although the Court allowed EPA to require its prior approval before new products were developed, it found all existing uses must be allowed to continue.

The U.S. Court found a ban of asbestos-containing products unwarranted because: 

• No significant human exposures to asbestos fibers would occur if the products were produced and used under controlled conditions;
• Substitutes for asbestos-containing products themselves posed potential human health risks that could be more significant than any potential risks from asbestos;
• Asbestos-containing products offered significant benefits not offered by substitute products.

Production and use of chrysotile-containing products, like production and use of many other chemicals that can pose risks if not adequately controlled, are regulated in the United States not only by EPA, but also by the Occupational Safety and Health Administration (OSHA) and the Department of transportation (DOT). EPA regulates air and water emissions from chrysotile production facilities and provides rules for disposal of chrysotile-containing waste. OSHA has established a comprehensive health standard for chrysotile that requires workers with potential exposures to be aware of and trained to minimize any risks and sets a stringent limit for airborne exposure. DOT regulates transport of chrysotile.

As a result of comprehensive regulation in the United States today, exposures to workers or the public are minimal and do not pose significant risk. At the same time, the public derives benefits from the unique qualities of this mineral as an effective and low cost raw material for construction and friction products.

THE FAIR Act

The American Congress is once again debating asbestos reform legislation. This time, it’s the « Fairness in Asbestos Injury Resolution Act », called the FAIR Act. If adopted by Congress, a national fund of US $140 billion will be put in place to pay off asbestos claimants, with the money of course industry-funded. These funds will serve to pay compensation to hundreds of thousands, if not of millions of plaintiffs.

Even before knowing the results of an exhaustive study, currently underway and headed by the US EPA on asbestos risk assessment, ban asbestos supporters have taken advantage of the exasperation of the people faced with the scandal in the system, to soflty bypass the role of EPA and attain their goal of an international ban of chrysotile.

Environmental Protection Agency and chrysotile

On May 30 of the year 2003, the Eastern Reasearch Group submitted to the Environmental Protection Agency (EPA), an organism based in Washington D.C., USA, a report to discuss a proposed protocol to assess asbestos-related risk. The whole document is available at 
www.epa.gov/superfund/programs/risk/asbestos/pdfs/asbestos_report.pdf (264 kb)

Eleven expert panellists participated to review the proposed protocol submitted by Drs Berman and Crump. The panel recommended that EPA proceed in an expeditious manner to consider the panellists’ conclusions and recommendations with a goal of having an updated asbestos risk assessment methodology.

Here are a summary of these recommendations.

• Measurement methods : For the last twenty years, continuing advances have been made in the application of exposure measurement technology for asbestos fibres, including the use of transmission electron microscopy (TEM) and allied techniques as an alternative to phase contrast microscopy (PCM). The proposed risk assessment incorporates these advances in the development of an exposure index. This represents a substantial advance over the existing methodology;
• Integration of exposure and risk assessment models : A key aspect of the proposed risk assessment methodology is a linking of specific exposure characterization methodology with exposure-response coefficients. It has been emphasized that any change in the exposure characterization metrics must be accompanied by changes in the exposure-response coefficients of the risk assessment models;
• Access to additional raw data sets : The panellists strongly recommended that EPA make every attempt to acquire and analyze raw data sets from key human epidemiological studies. Where possible, it would also be desirable to obtain fibre exposure information (length and diameter) for these re-analyses;
• Fibre diameter : The proposed risk assessment methodology uses a diameter cut-off of 0,5 micrometers. There was a general agreement that the diameter cut-off should be between 0,5 and 1,5 micrometer. This issue is deserving of further analysis;
• Fibre length : The proposed model index assigns zero risk to fibre less than 5 micrometer in length. Fibres between 5 and 10 are assigned a risk that is one three-hundredth the risk assigned to fibres longer than 10 micrometers. Panellists agreed that there is a considerably greater risk for lung cancer for fibres longer than 10 micrometers. However, the panel was uncertain as to an exact size for length and the magnitude of the relative potency;
• Fibre type : Mesothelioma : Panellists supported the use of different relative carcinogenic potencies for different fibre types. They unanimously agreed that the available epidemiology studies provide compelling evidence that the carcinogenic potency of amphibole fibres is two orders of magnitude greater (100x) than that for chrysotile fibres. Lung cancer : Panellists had differing opinions on the interferences that can be made on the relative potency of chrysotile and amphibole fibres. Some panellists supported the finding that amphibole fibres are five times or more potent for lung cancer than are chrysotile fibres. Other panellists did not think the statistical analyses in the draft methodology document supports this relative potency and wondered if additional review of the epidemiological data might identify factors other than fibre type that provide further insights on the matter;
• Cleavage fragments : The general view is that data indicate that durability and dimension are critical to pulmonary pathogenesis. Therefore, it is prudent at this time to assume equivalent potency for cancer in the absence of other information to the contrary;
• Other amphiboles : The panel agreed with the report’s conclusion that the potency of currently regulated and unregulated amphibole fibres should be considered equal based on the reasoning that similar durability and dimension would be expected to result in similar pathogenicity;
• Methods : The panellists urged exploration of alternative exposure-response models other than the lung cancer and mesothelioma risk models EPA has been using since 1986. This would possibly include non-linear response model, examination of separate effects for concentration and duration, time since first exposure, time since cessation of exposure, possibly dropping the “factor”, and different methods for measurement error. Exploration of non-linearity should also include shape of the curve in the low exposure area. Panellists recommended meta-regression using original exposure-response coefficients, in which predictor variables include the estimated percentage of amphiboles, percentage of fibre greater than 10 micrometers, and categorical grouping of studies according to quality. Meta-regression will allow simple inspection of likelihood to consider the importance of different predictor variables. Sensitivity analyses should be conducted in which the inclusion or exclusion of specific studies or groups of studies is evaluated;
• Cigarette smoking : Most panellists felt strongly that future analyses need to pay more attention to the effects of smoking on the lung cancer exposure-response model and extrapolations to risk. The panellists noted that smoking is the primary cause for lung cancer, but the lung cancer dose-response relationship for smoking is complex due to the effects of smoking duration, intensity and cessation. With respect to applying the model to make risk projections for any future cohort, the background rate of lung cancer employed in the model need to be carefully determined to capture the smoking behaviour of the cohort;
• Localized tremolite exposures : During the course of public comments, the panel received input from several individuals who expressed concerns about environmental exposures to tremolite asbestos from localized geological formations. While the panel was not in a position or charged with the evaluation of this issue, the panel did feel that this was a potentially serious matter deserving of attention by the appropriate public health authorities. Evaluation of these kinds of situations would benefit from the use of the improved risk assessment methodology being considered.

EPA was created in 1970. It is now employing some 18 000 citizens. There mission is to protect America’s health and environment.

SEE ALSO... The Asbestos dilemma: I. Assessement of risk The Asbestos dilemma: II.The ban