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What's New with Hexavalent Chromium?

By Tony Watson, CIH, CSP

First, a little background information…

As ordered by the Third Circuit Court of Appeals, OSHA recently published a final rule for hexavalent chromium. The final rule was supposed to have been issued by January 2006, but OSHA’s response to Hurricane Katrina apparently played a role in the delay until February 28, 2006.

The proposed rule, published in August 2004, indicated an 8-hour time-weighted average Permissible Exposure Limit (PEL) of 1 µg/m3 and an Action Level of 0.5 µg/m3 for all forms of hexavalent chromium was imminent. The proposed limits were in line with current American Conference of Governmental Hygienists (ACGIH) Threshold Limit Values (TLVs) for “slightly soluble” forms, believed to be associated with the highest risk of lung cancer (see Figure 1). This was a considerable reduction from the 1 mg/10 m3 PEL-Ceiling that dates back to a 1943 ANSI standard. Stoichiometric conversion of the old PEL equates to a limit of 52 µg/m3, as a Ceiling. This limit was intended to prevent workers from developing dermatitis, skin ulcerations, and perforations of the nasal septum. The 1 mg/10 m3 Ceiling Limit did not account for the cancer risk associated with hexavalent chromium.

Figure 1: Solubility vs. Carcinogenicity

Compound

Formula

Solubility

Strontium Chromate (SrCrO4) Slightly Soluble
Calcium Chromate (CaCrO4) Slightly Soluble
Lead Chromate (PbCrO4) Insoluble
Zinc Chromate (ZnCrO4) Insoluble
Ammonium Dichromate ((NH4)2Cr2O7) Soluble
Chromium Trioxide (CrO3) Soluble
Potassium Chromate (K2CrO4) Soluble
Potassium Dichromate (K2Cr2O7) Soluble
Sodium Chromate (Na2CrO4) Soluble
     

Fast forward to the present...

Citing technologic and economic feasibility issues not considered in the proposed rule, OSHA decided upon an 8-hour time-weighted average Permissible Exposure Limit (PEL) of 5 µg/m3 and an Action Level of 2.5 µg/m3 for all forms of hexavalent chromium. The final rule also has requirements for periodic air sampling, establishment of regulated areas, and medical surveillance, based on exposures. Other requirements not directly tied to exposure monitoring results are the prohibition of rotation of workers to achieve compliance with the PEL and restrictions of certain cleaning methods such as dry sweeping and use of compressed air to clean surfaces. Protective work clothing and equipment is required when a hazard is present due to skin or eye contact with hexavalent chromium. In these instances, hygiene areas and change rooms are also required. Employees potentially exposed to hexavalent chromium must also be trained so they can demonstrate sufficient knowledge of the standard and the purpose and description of the medical surveillance program required by the standard.

There is still a little time left…

All employers covered under the General Industry Standard (CFR 1910.1026) have until May 31, 2010 to implement engineering controls where needed to reduce exposures to or below the PEL. Employers with 20 or more employees must be in compliance with other requirements of the new standard by November 27, 2006. For smaller companies with 19 or fewer employees, compliance with other requirements of the standard must be attained by May 30, 2007.

More information...

Workplace Hygiene has worked closely with companies in aerospace, stainless steel, electroplating, textile, wood preservation, and other industries in evaluating and controlling employee exposures to hexavalent chromium. If you have questions regarding hexavalent chromium please contact Tony Watson, CIH, CSP to learn more.




   
 

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