OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

June 27, 1997

The Honorable Bud Cramer
U.S. House of Representatives
2416 Rayburn Building
Washington, DC 20515-0105

Dear Congressman Cramer:

Thank you for your letter of January 16, 1997, regarding the Occupational Safety and Health Administration's (OSHA) Methylene Chloride (MC) Standard. We wish to assure you that OSHA is aware of the concerns you raise regarding the impacts of the MC rule and has addressed these concerns in the preamble to the final rule and the Final Economic Analysis. We would like to take this opportunity to clarify some misimpressions being raised about the risks of MC exposure and the methods available to reduce those risks to the U.S. workforce. Please accept our apology for the delay in this response.

The OSHA MC rulemaking was initiated in 1986 when the Agency published an Advance Notice of Proposed Rulemaking in response to a petition from the United Auto Workers (joined by several other unions) to regulate MC because it was shown to be carcinogenic in laboratory animals. In 1991, OSHA published a Notice of Proposed Rulemaking which included a proposed 8-hour time-weighted average (TWA) permissible exposure limit (PEL) of 25 ppm, a short-term exposure limit of 125 ppm and ancillary provisions covering exposure monitoring, medical surveillance, regulated areas, etc. In 1992, the Agency convened informal public hearings on the proposed standard in Washington, DC and San Francisco, CA. In addition, the rulemaking record was opened several times to receive public comment on feasibility and risk assessment issues.

The final MC rule (published in the Federal Register on January 10, 1997 (62 FR 1493)) is based on careful evaluation of all available information, including information submitted to the record by representatives of small businesses. OSHA's rulemaking record (now in excess of 48,000 pages of information) contains extensive data regarding the feasibility of compliance with the final rule, including information on substitutes for MC, modifications to control or process equipment and alterations in work practices. Many of these feasible methods of compliance are as simple and common-sensical as providing adequate ventilation, or covering tanks and containers when not in use. Data in the record indicates that the final MC regulation is feasible in all affected industries. OSHA must base its findings on its rulemaking record and must promulgate a regulation that is technologically and economically feasible for all affected industries.

OSHA has been particularly concerned with the ability of small businesses to comply with the MC standard. Therefore the Agency has streamlined requirements to reduce potential economic and paperwork burdens on such employers, including extending compliance deadlines for employers with fewer than 20 employees. Many of the actions taken by OSHA to reduce the potential compliance burdens in the final MC rule were the direct result of input to the MC rulemaking by small employers.

OSHA has thoroughly evaluated all information submitted to the record concerning the health effects of MC, including cancer, and has used this information to conduct a quantitative risk assessment using physiologically-based pharmacokinetic (PBPK) information and cutting-edge statistical methodologies. Indeed, industry groups have repeatedly asked OSHA to adopt a PBPK approach to its MC risk assessment; OSHA has determined that the data base (notably including the new data submitted by the Halogenated Solvents Industry Alliance (HSIA)) is now sufficiently reliable and detailed to support such an approach. The Agency has determined that the risks to workers exposed to MC at levels greater than 25 ppm as an 8-hour TWA greatly exceed the level of risk deemed significant by the Supreme Court and would be clearly unacceptable. The evidence that a limit of 50 ppm would be severely inadequate to protect workers includes a wealth of animal bioassay data, numerous studies detailing the human metabolism of MC to carcinogenic products, risk assessment based on these data, and several epidemiologic studies that suggest an elevated risk of biliary cancer and astrocytic brain cancer in MC-exposed workers.

After completing its analyses, OSHA briefed the scientific staff from the Environmental Protection Agency, the Food and Drug Administration, the National Institute for Environmental Health Sciences, and the Consumer Product Safety Commission on the Agency's analysis of the submitted studies and OSHA's revised risk assessment. The professionals at these meetings agreed with OSHA's characterization of the risks posed by MC and specifically praised the Agency for incorporating the specific type of additional information (PBPK data) that the HSIA and others had advocated be used.

The PBPK data and model structures used as the basis of OSHA's final risk assessment were available in the record for review and comment. Several PBPK models were submitted to the record and elicited comments during the MC rulemaking. In the course of drafting the final risk assessment, OSHA reanalyzed all of the available and appropriate data in the record, but did not revise the underlying assumptions upon which its preliminary risk assessment and the PBPK-based assessments submitted to the Agency relied. In October 1995, OSHA re-opened the rulemaking record specifically for the purpose of incorporating mechanistic data submitted to the Agency by the HSIA. OSHA requested comments on how that data should be used in characterizing the risks of MC. Based on its analysis of the data and comments received, OSHA made the appropriate changes to its risk assessment. In addition, the rulemaking record was opened serval times to receive public comment on the key issues raised on feasibility and MC risk assessment.

OSHA's final MC risk assessment estimates that at lifetime occupational exposure to 25 ppm, the additional risk of dying of cancer is 3.6 deaths per 1000 workers. OSHA's goal, where technologically and economically feasible, is to reduce cancer risks to below 1 death per 1000, consistent with Supreme Court guidance. Other agencies with statutory obligations to protect the general population aim for levels of protection more than 100 times greater than the level used by OSHA. Although the risks at 25 ppm are significant, the Agency is currently constrained from reducing the PEL to below 25 ppm due to a lack of definitive evidence documenting the feasibility of lower limits. OSHA has promulgated the standard at 25 ppm, in order to reduce risks and because the Agency has determined that 25 ppm is technologically and economically feasible across industry sectors.

Thank you for bringing your concerns to our attention. Your interest in occupational safety and health is greatly appreciated.


Adam M. Finkel, Sc.D.
Health Standards Programs

January 16, 1997 Mr. Joseph Dear
Assistant Secretary
Occupational Health & Safety Administration
Third Street and Constitution Avenue, NW
Washington, DC 20210

Dear Mr. Dear:

I am writing about the Occupational Safety and Health Administration (OSHA) workplace standard for methylene chloride which I understand OSHA intends to issue shortly. I have constituents who have indicated they would have significant problems in complying with a 25 parts-per-million limit. I would appreciate the opportunity to explore my concerns with you before the final standard is issued.

Specifically, I understand the risk assessment and the economic analyses that are the basis for the rule have changed significantly over the past few months. OSHA should give the public an opportunity to comment on the revised scientific and economic analyses before taking final action on the methylene chloride standard, unless there is a statutory or judicial deadline that precludes OSHA from taking this action. This would also allow OSHA to have the benefit of participating in the interagency characterization of the potential risk posed by methylene chloride under the EPA guidelines, expected to be completed in 1997.

In addition, the Small Business Regulatory Enforcement fairness Act requires the OSHA seek congressional review of the methylene chloride standard. If the methylene chloride standard is issued without giving the public an opportunity to review and comment on the revised scientific and economic analyses, this review may be extensive. I urge you to take the time to address valid constituent concerns, so there can be widespread congressional support for OSHA's final action.


Bud Cramer
Member of Congress