Dermal Exposures to Chemicals
11/2/2020
Skin exposure to chemicals in the workplace is a significant problem in the U.S. Both the number of cases and the rate of skin disease in the U.S. exceeds recordable respiratory illnesses. In 2018, 25,000 recordable skin diseases were reported by the Bureau of Labor Statistics (BLS) at a rate of 2.2 injuries per 10,000 employees, compared to 19,600 respiratory illnesses with a rate of 1.7 illnesses per 10,000 employees.
Most chemicals are readily absorbed through the skin and can cause systemic health effects while contributing to the exposures one may receive via inhalation. Many studies indicate that absorption of chemicals through the skin can occur without being noticed by the worker. In many cases, skin is a more significant route of exposure than the lung. This is particularly true for non-volatile chemicals which are relatively toxic, and which remain on work surfaces for long periods of time. And while the number of occupational illnesses caused by skin absorption of chemicals is not known, it is argued that this route of entry into the body may account for an estimated 60,000 deaths and 860,000 occupational illnesses per year in the U.S..
Dermal exposure is addressed in all the major OSHA standards: This includes General Industry (29 CFR 1910), Maritime (29 CFR 1915, 1917 and 1918), Construction (29 CFR 1926), as well as Identification, Classification, and Regulation of Potential Occupational Carcinogens (29 CFR 1990).
But while OSHA regulations promote specific protective practices for airborne contaminants, such as permissible exposure limits (PELs) and respiratory protection, when it comes to protecting the American worker from exposures to the skin, face and eye, the requirements may be described as generic. For instance, the OSHA general industry regulation for hexavalent chromium or Cr(VI): 29 CFR 1910.1026, specifies a PEL of 5.0 micrograms per cubic meter (µg/m3) and an action limit of 2.5 µg/m3. In addition, it is mandatory that Cr(VI) regulated areas are established where industrial hygiene exposure assessments are performed. In contrast, for dermal exposures to Cr(VI) the same regulation merely provides general specifications.
“Where a hazard is present or is likely to be present from skin or eye contact with chromium (VI), the employer shall provide appropriate personal protective clothing and equipment at no cost to employees and shall ensure that employees use such clothing and equipment.”
This disparity between inhalation and dermal exposure assessment and control requirements seems to be constant throughout the OSHA regulations; that is, a definitive assessment method to determine the ability of a chemical causing adverse health effects through dermal contact lacks the specificity for which is described for airborne concerns.
Nevertheless, dermal exposure evaluations have been explored over the years and have been (broadly) categorized into two distinct methods: direct and indirect.
Direct exposure evaluation: Meaning to assess what is deposited onto the skin. The most common direct method is the use of dermal dosimeters in the form of either patches or whole body suits. Other direct evaluation methods include skin washes and wipes, and the video detection of fluorescent tracers.
Indirect exposure evaluation: Indirect means estimating dermal dose either as attributable to some biologic indicator that is actually measured or that which could potentially result from a contaminant measured on an accessible surface. Indirect methods refer primarily to measuring a surrogate material that produces a biologic response such as cholinesterase activity in blood or urinary excretion, but also include measuring surface contamination.
It is obvious that surface contamination determination is more of a qualitative assessment than quantitative. In other words, determining dermal contamination – presently – is a yes/no decision. This means that a positive analysis for a chemical being detected on a hand, arm or other body part, will not allow for a complete understanding of the specific effect that may develop from such an exposure. Of course, regardless of any specific measurement, the detection of a contamination, such as an organic solvent or caustic material, would indicate that the controls used to protect workers is not adequate; or quite possibly, that there was even a lack of controls applied. Having the proper gloves, coveralls, booties and eye protection should be part of a standard protocol to protect persons from dermal exposures.
Monitoring skin surfaces in the field for radiation control is standard protocol direct reading instrumentation has the capability to not only detect radiation levels, but to quantify the amount of contamination comparing these measurements to published occupational health values. Yet, direct reading on skin surfaces in the world of industrial hygiene is still in the development (or rather, wishful) stage. And while there are companies out there that are focused in advancing such technology, a definitive method to determine non-radiological contamination on skin surfaces is, at best, in the infancy stage.
Meanwhile there are regulations that specify surface contamination requirements. For instance, the DOE housekeeping limits for beryllium work areas (10 CFR 850.30) and the release criteria for equipment of materials in beryllium areas (10 CFR 850.31). In addition, there are non-occupational regulations that specify appropriate surface level limits through Housing and Urban Development standards for lead-based paint and the EPA limits for PCBs during clean-up operations through the Toxic Substances Control Act. However, these regulations specifically address surface contamination on building surfaces (windowsills, workstations, etc.) and on equipment and materials, and clearly is NOT intended for dermal controls.
The problem is defining a relationship between dermal contamination and dose. To date, those studying dermal exposures have found poor correlations between the detection of contaminants on the skin and adverse effects. At the same time, while organizations such as OSHA and the American Conference of Governmental Industrial Hygienists have listed skin notations for specific chemicals (indicating that such materials can be absorbed through the skin), no specific amount (either as a mass or volume) has been specified.
So, the problem of determining dermal exposure concentrations remains a weak link in the field of Occupational S&H. Nevertheless, through an effective PPE program, where the right selection, use and maintenance and care of such items as goggles, coveralls, gloves, booties, etc., can help to ensure dermal exposures to chemicals are properly controlled. This requires a thorough hazard assessment of the anticipated contaminants-of-concern, work tasks as well as employee use (this includes proper donning and doffing) in combination with a continuous assessment of the efficacy of how well these aspects are adhered. Until the day when dermal exposures can be assessed to the degree needed, using the right PPE, as well as prudent work practices, as well as other administrative controls (training, work procedures, etc.) must be the cornerstones to ensure dermal exposures are properly controlled.
There’s no point in burying a hatchet if you’re going to put up a marker on the site
Sydney J. Harris (American Journalist)