Glycol Ether Hazards

The National Toxicology Program (NTP) recently released a report on chronic studies of the dangers of 2-Butoxyethanol, also know as butyl cellosolve.1 Butoxyethanol belongs to a family of glycol ethers. It is used extensively as a solvent in surface coatings such as lacquers, enamels, varnishes, and latex paint; in paint thinners, paint stripping formulations, and inks; and in degreasers and industrial and household cleaners. It was nominated for study by the UAW because of its use in the auto industry and because of the potent toxicity of the related chemicals ethoxy- and methoxy-ethanol. CPSC also nominated butoxyethanol for testing.

Exposure to paint solvents should be minimized. The operation in this picture would be improved by containing overspray in an enclosure and using less pressure to the gun. Less toxic methods are also available.

Rats were exposed to 2-Butoxyethanol by inhalation at concentrations of 0, 31.2, 62.5, or 125 ppm for 104 weeks. A consistent exposure-related effect on the blood forming system was an exposure concentration-related anemia present at 3, 6, and 12 months, with females more affected than males. Significant increases in bone marrow cells were observed at 125 ppm. Exposure-related degeneration of the olfactory epithelium and pigmentation of the liver were observed in male and female rats at exposures as low as 31.2 ppm, the lowest dose tested.

Mice were exposed to 2-Butoxyethanol by inhalation at concentrations of 0, 62.5, 125, or 250 ppm for 104 weeks. A consistent exposure-related effect on the blood forming system was an exposure concentration-related minimal anemia present at 3, 6, and 12 months, with females affected slightly more than males. Exposure related abnormal cell growth in the stomach, and pigmentation of cells in the liver, was observed at 62.5 ppm, the lowest dose tested. Damage to the nose, abnormal cell growth in the bone marrow and spleen were also observed.

In genetic toxicology tests, 2-Butoxyethanol did not induce effects in the tests given.

Regarding cancer, the investigators concluded that there was some evidence of carcinogenic activity in male mice based on increased incidences of hemangiosarcoma of the liver. A marginal increase in the incidences of forestomach squamous cell papilloma and an increase in the incidences of hepatocellular carcinoma may have been exposure related. There was some evidence of carcinogenic activity in female mice based on increased incidences of forestomach squamous cell papilloma or carcinoma (mainly papilloma). There was equivocal evidence of carcinogenic activity in female rats based on the increased combined incidences of benign or malignant pheochromocytoma (mainly benign) of the adrenal medulla. There was no evidence of carcinogenic activity in male rats.

UAW Commentary These new results add to the concern for butoxyethanol, and confirm that the present OSHA exposure limit doesn’t protect. NIOSH had previously warned that butoxyethanol can damage the eyes, skin, respiratory system, central nervous system, hematopoietic system, blood, kidneys, liver, and lymphoid system, and that dangerous amounts could be absorbed through the intact skin. The NIOSH recommended exposure limit is 5 ppm, the ACGIH TLV is 25 ppm, while the OSHA standard is 50 ppm. In this study, adverse effects were observed in rats at exposures as low as 30 ppm, the lowest dose tested. The carcinogenicity findings have not been reviewed for classification by IARC or the NTP. However, elevations in two experiments suggest that butoxyethanol should be considered reasonable anticipated to cause cancer in people. In addition, the findings trigger a Hazard Communication requirement to disclose butoxyethanol as an ingredient when present at 0.1% in mixture, that such mixtures be labeled carcinogenic, and that hazard communication training and MSDS’s be updated to disclose this new hazard. The UAW is not prepared to recommend a new PEL for butoxyethanol. UAW locals should check paint and adhesive ingredient lists for butoxyethanol, and request current air sampling be conducted by a method sensitive to 1 ppm for butoxyethanol. 1 TR-484 Toxicology and Carcinogenesis Studies 2-Butoxyethanol (CAS NO. 111-76-2) in F344/N Rats and B6C3F1 Mice (Inhalation Studies)

 

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