STLE Reviews Formaldehyde Concerns


ST. LOUIS-The search for cost-effective alternatives to formaldehyde-releasing biocides in metalworking fluids, which face severe regulatory restrictions, drew considerable attention at the STLE 2012 annual meeting earlier this month.

These products represent 70 to 80 percent of the total volume of antimicrobials used in metalworking fluids, according to Fred Passman of Biodeterioration Control Associates, Inc. of Princeton, N.J. By mid-June, they could be off the Canadian market while their fate in the United States remains uncertain.

In particular, Passman said, Based on a 2010 draft ofthe U.S. Environmental Protection Agencys Integrated Risk Information System report for formaldehyde, the EPAs Office of Pesticides Programs planned to limit the maximum permissible dose for formaldehyde-condensing biocides to 500 ppm, compared to the current usage of up to 2,500 ppm.

The products are completely ineffective at 500 ppm, he said, while also observing that the EPA has tabled that plan for the moment, pending final approval of the IRIS report.

Formaldehyde-condensing biocides have been used for decades to control microbial contamination in metalworking fluids because they are economical and effective against a wide variety of microbes. The concern over formaldehyde-condensates in metalworking fluids is that formaldehyde is classified as a human carcinogen.

However, as Peter Wachtler of Lanxess, Leverkusen, Germany, pointed out, There have been very few cases where human carcinoma can be related to formaldehyde exposure, especially in the metalworking environment where worst-case exposure levels are quite low.

He added that despite a lack of hard data to back up restrictions, the U.S. EPA seems determined to proceed with its regulations.

Europe is also placing regulatory pressure on suppliers and users of thesemicrobiocides, according to Wachtler. European nations, especially France, are determined to move formaldehyde to a more severe labeling category, he said.

He went on to describe the potential of parachlorometacresol (PCMC) and ortho-phenylphenol, two phenolic compounds, as replacements for formaldehyde. Testing at Lanxess indicates that PCMC provides broad spectrum coverage against bacteria, mold and yeast while ortho-phenylphenol shows strong activity against yeasts and mold fungi but lower activity against bacteria.

Christine McInnis and Terry Williams of Dow Microbial Control, Springhouse. Pa., summarized the current regulatory climate and described their work in evaluating alternative biocides. They reviewed the critical properties required of an effective biocide, concluding that benzisothiazolinone (BIT), morpholines, methylisothiazolinone (MIT) and phenolics were viable alternatives, although each had pros and cons that should be evaluated before being used. They also indicated that the combination of BIT and nitro-dimorpholine is easy to formulate into concentrates and is effective against both bacteria and fungi.

Lubrizols Uwe Falk of Hamburg, Germany, described an EPA-registered biocide based on methylenebismorpholine (MBM) chemistry that is currently available in 36 countries. Called Contram ST-1, the biocide is used as a concentrate in closed systems. Falk said that the product forms stable emulsions and is effective even after six months storage.

Alan Eckard of Monroe Fluid Technology, Hilton, N.Y., covered the selection of biocides for metalworking fluids used on nonferrous metals. He said that these fluids can be more difficult to protect from microbial growth because nonferrous metals respond especially well to the use of compounds that are nutrients for microbes such as esters, fats and triglycerides in the form of vegetable oil lubricity additives.

Eckard described the effectiveness of alkyl or alkanolamines that interfere with metabolic processes in most microbes. In many cases, these agents show low to moderate toxicity to humans and appear to be of low risk at typical use concentrates, he said.