Methylene chloride is identified on MSDS sheets and can labels as CAS #75-09-2. According to industry expert Dr. Harry Elston, methylene chloride is a clear, colorless liquid with an odor resembling that of chloroform. It is an extremely good solvent on a wide variety of contamination. It is not miscible in water, it has a moderately high vapor pressure and a heavier-than-air vapor density. It is widely used in industry because it is considered nonflammable under normal conditions.

Methylene chloride has relatively low acute toxicity (LD50 (rat, oral) = 1600 mg/kg) and is only a mild skin irritant. These excellent solvating properties and modest toxicity ratings have historically made methylene chloride one of the most convenient solvents for the electronics industry, furniture and paint stripping, polyurethane foam manufacturing and general cleaning/degreasing.

Methylene chloride's carcinogenic properties are still being debated. It has been identified as Group 2B, "possible human carcinogen" by the International Agency for Research on Cancer (IARC). It has been classified as a "suspected human carcinogen" by the American Conference of Governmental Industrial Hygienists (ACGIH) and "anticipated human carcinogen" by the National Toxicology Program. Only over the last few decades has long-term, low-level MC exposure been linked to chronic pulmonary, liver and CNS diseases. For this reason, OSHA has stepped in to stringently limit worker exposure.

Todd Hyten, in an article on the IndustryNet web site, notes that "Methylene chloride exposure has caused cancer in laboratory animals. Other risks in humans include chronic central nervous system effects and cardiac damage, according to OSHA." The new standards, according to the agency, would save 34 lives a year. But some critics charge that the new standards are based on "inconclusive scientific evidence." Peter Voytek, executive director of the Washington-based Halogenated Solvents Industry Alliance, said that although studies showed that the solvent caused cancer in mice in extremely high concentrations, results were not duplicated with other laboratory animals, including rats and hamsters.

Adam Finkel, OSHA's director of health standards, said countered that claim by noting that OSHA took into account recent studies that pointed to metabolic differences between mice and humans that may have affected lab results. "We made use of new data supplied by industry suggesting that workers are less sensitive to the carcinogenic effects of MC than laboratory mice," said Finkel. "Workers exposed above 25 ppm over a working lifetime face an intolerably high cancer risk."

In an article in Compliance Magazine, Susan E. Neff reported that "the cost of implementing the new standard has not been determined, but at least one of its critics estimate the cost in the billions -- while others say it's too soon to tell." The cost for the new standard will average $101 million each year, or $426 per exposed worker, according to OSHA. Exposure can be limited, according to OSHA, by using ventilation systems or cover tanks.

But others disagree. Hyten notes in his research that OSHA may have understated the cost of the regulations. "We're still very concerned at the high capital cost especially to manufacturing," he quotes Anita Drummond with the Small Business Administration's Office of Advocacy. "We feel that the annualized cost may meet $15,000 [per employee]," said Drummond. Smaller firms with heavy usages, such as furniture stripping companies, may have to seek outside financing to buy equipment or systems to meet the new standards, Hyten concludes.

Mary Reed, manager of Legislative Affairs for the National Federation of Independent Businesses (NFIB), said she has concerns about the effect of a sweeping rule that would force small businesses to operate under the same guidelines as those imposed on larger businesses. "It's another layer of government. It's one more regulation -- one more standard in a host of regulations," Reed said. "We have heard from our members and they rate concern over this regulation as number three behind taxes and health care. We argued during the stakeholders meeting that especially for small businesses in a safe industry there should be a small business exemption."

Dr. Elston notes that many employers found it difficult to meet the mandated start-up dates for the installation of proper engineering controls. Prior to the legal challenges to the new standard, employers were faced with solving the exposure problem twice: first, installing temporary respiratory equipment and secondly while constructing long-term solution to reduce exposure. One of the proposed changes to the regulation was to allow most employers a few extra months to install permanent, engineering controls while relaxing the respirator requirements, as long as the short-term exposure level (STEL) of 125 ppm is not exceeded and work practices are modified to further reduce exposure.

The revised standard's lower exposure can have a significant, though short-term, negative impact on employers while they design and implement solutions to meet the new toxicity rules, Dr. Elston feels. However, "the long-term benefit of a healthy and more productive workforce derived from the installation of engineered safeguards to minimize exposure should result in overall financial gain."

Please call, fax or email us at MicroCare Marketing Services
for more information about our full line of cleaning answers.