Under your skin
More than 100 chemicals with OSHA permissible exposure limits for inhalation hazards are also known skin permeants. Like the effects of breathing toxic fumes, when one of these substances is absorbed into the blood stream through the skin, the result can be serious -kidney or liver disease, neurological or reproductive disorders, or cancer.
For instance, about a teaspoonful of styrene (3 milliliters) splashed on a worker’s skin can deliver the same dose as the eight-hour inhalation exposure limit -50 parts per million. Just touching a surface contaminated with 1.5 micrograms per square centimeters of the suspected carcinogen acrylamide -a quantity about one-millionth the weight of a paper clip- could equal inhaling one day’s permissible exposure limit, 0.03 milligrams per cubic meter.
But other than a "skin notation" alongside the PEL for permeating chemicals OSHA offers nothing to help safety and health pros trying to deal with dermal exposures. No limits tell you how much of a chemical can safely contact workers’ skin. And even if skin exposure levels were established, no tool like an air monitor exists to measure them. Likewise, no NIOSH standard -like the one the agency recently updated for respiratory protective equipment- exists to help managers sort through the variety of glove materials available.
NIOSH researcher Mark Boeniger calls the inattention to dermal exposures "one of the greatest failures of OSHA and NIOSH." Other skin experts accuse universities of contributing to the problem by glossing over dermal absorption when training young health and safety professionals.
"If you talk to 100 industrial hygienists, 95 percent of them will know what their plant’s airborne exposures are," says dermal absorption expert Tom Klingner. "But ask them whether they’re protecting workers from dermal exposures and they have no idea." Industrial hygiene graduate students have told Klingner they learned more about dermal exposures during a half-hour conversation with him than they did during their grad school career.
The price of ignorance is that many workers are left with only Mother Nature’s thin line of defense. Little more than their skin’s own stratum corneum -a protective layer no thicker than a strand of hair- comes between them and the toxics they touch. What’s worse is that some common ways to protect skin -wearing gloves, applying barrier creams and scrubbing clean after work- don’t always do the job. In fact, they can raise the risks of dermal absorption.
To help you out until science lends more support, Industrial Safety & Hygiene News talked to experts about dos and don’ts for dealing with dermal exposures.
Help is on the wayThere’s no question industry needs help protecting workers’ skin. The health effects of dermal absorption are so difficult to trace and can take so long -sometimes a lifetime- to detect, that illness data is impossible to collect. OSHA doesn’t know how many people are exposed to skin permeating chemicals at work. But the fact that dermal diseases and disorders like dermatitis were long the most oft reported job illness in the U.S. (only recently displaced by cumulative trauma disorders) indicates that skin protection is overlooked in more than a few workplaces.
Dermal issues are starting to come under government scrutiny: ·
- In a document announcing plans to begin new research on skin irritants and allergens, NIOSH pointed out the need for "improved field methods for measuring permeation of skin by individual substances and mixtures." A source there says at least six scientists will be hired to assist the meager staff of three now dedicated to dermal research. ·
- In April, EPA asked chemical manufacturers to test dermal absorption rates for 80 skin-permeating substances. If manufacturers don’t volunteer the data, EPA can, under the Toxic Substances Control Act, demand it. ·
- That information will be useful to OSHA when the agency updates its permissible exposure limits or establishes quantitative methods for limiting dermal exposures -a possibility made remote by the many variables that would have to be taken into account, according to two government researchers.
Detecting dermal exposuresUntil NIOSH findings, EPA data gathering, or OSHA standard setting offer any real guidance, you’re on your own. Your task is indeed daunting: dermal dangers can be as obvious as a chemical splash on a torn glove, or as inconspicuous as contaminated safety glasses rubbing the thin skin behind the ears.
Just getting workers to comprehend dermal absorption can be difficult. Inhalation exposures are easy enough to understand: Everyone knows a sneeze can pass a cold through the air. Most people recognize the dangers of breathing cigarette smoke. So it’s not a stretch to make the case that chemical-contaminated air can be bad for you. But good luck convincing a worker that holding a carbon disulfide-contaminated tool in a bare hand day after day can damage his sperm.
Tom Klingner recalls the irony of watching a gardener spray pesticides on flowers outside an industrial hygienists’ convention in Anaheim, Cal., two years ago: "The guy wore hip boots and gloves while he sprayed. When he was done, he went to his truck, pulled off a glove, then yanked off the other glove and both boots with his bare hands." Providing protective clothing isn’t enough, Klingner says. Educating workers and changing their behavior is the other half of the battle.
Trickier still can be the task of tracking the source when employees are dermally exposed. In the polyurethane industry, where the suspected bladder carcinogen methylene bis chloro aniline (MOCA) is a common hazard, the Polyurethane Manufacturers Association has long supported voluntary urine monitoring to detect exposures. Klingner’s firm, Colormetric Laboratories in Des Plaines, Ill., runs urine tests for several polyurethane clients who he says have "set the standard for all industries." Consider a few of his sleuthing stories: ·
- Urine tests at a California maker of cast polyurethane wheels -the sort that make in-line skates skate- revealed that office workers were suffering MOCA exposures. Traces of the chemical appeared in the urine of secretaries who never stepped near the manufacturing floor. Surface swipes identified the source: paperwork. Workers in the plant who signed paperwork with contaminated gloves passed along the MOCA to the front office. ·
- At another plant, Klingner was puzzled to find that among maintenance workers tested for MOCA exposures, the two with the highest exposures didn’t even work in contaminated areas. Eventually he discovered they were snitching -with their bare hands- tools from the contaminated toolbox of a co-worker whose exposure level was much lower, and who always wore gloves. ·
- An employee whose job at another cast polyurethane plant was to meter material out of a mixing head and hand pour it into molds changed from street clothes into protective clothing before work. When tests showed high exposure levels, Klingner discovered the worker’s boots had been splashed with chemicals: The man was contaminating himself every morning pulling on his boots, and compounding the problem by wearing gloves over his dirty hands all day.
Solutions for these cases were simple: Encase paperwork in plastic folders that get removed before passing along from the plant to the office; paint tools used in contaminated areas red as a warning to don gloves; and keep reusable PPE clean and use disposable shoe covers for chemical splashes. The real challenge is educating workers to prevent the exposures in the first place.
These dos and don’ts can help minimize risks to the skin:
- Keep skin clean and healthy. Abraded, irritated, or even sunburnt skin is more susceptible to dermal absorption. Use products tailored to the industrial market, not just cosmetic moisturizers, says Eleanor Fendler, Ph.D., product development manager for skin care company Gojo Industries. ·
- Keep hands and skin dry. Moisture on the skin, like sweat, can enable permeation, as can high temperatures. ·
- Choose gloves and protective materials carefully. Some chemicals, like lacquer thinner, can permeate just about any glove when microscopic molecules break through individual molecules of the protective film on the glove. But beware, too, of over protecting. A glove that is too thick or bulky only contributes to exposure risks when workers remove it to perform jobs requiring dexterity or tactility. ·
- Watch out for glove degradation. Don’t rely on a glove once its physical property changes, says Nelson Schlatter of glove maker Ansell Edmont. "Degradation is easy to spot," he says. "The glove will either swell up and get soft, or shrink and harden." Flexing a glove can increase the permeation rate and breakthrough time by ten, according to NIOSH’s Boeniger. And, of course, chemicals can penetrate visible holes in gloves.
- Don’t use solvents to clean chemicals off hands. Solvents can damage the skin, making it more readily permeable, says Fendler. ·
- Don’t put gloves on contaminated hands. Gloves can force penetration of chemicals already on the hands and increase the likelihood of dermal penetration up to five times, according to Boeniger. ·
- Don’t apply moisturizer or barrier cream to contaminated skin. "If an auto mechanic puts barrier cream on his hands after he changes the oil, he can be causing himself really serious damage by forcing penetration," Fendler says. ·
- Don’t use barrier creams in the place of gloves. Barrier creams can be an addition to a skin protection regime, but studies recommend against substituting them for gloves.
Sidebar: 12 steps to reducing dermal exposuresInitial exposure survey:
1. Locate areas and jobs in the facility where hazardous chemicals are used.
2. Check work surfaces, tools, production equipment, chemical storage and transfer areas with "swypes"* to verify the need for PPE and requirements for personnel entering contaminated areas. Mark regulated areas and equipment.
3. After determining areas where potential for skin exposure exists, survey outside areas and surfaces for contamination transfer. Observe the process flow:
4. Check the product with "swype."
5. Check equipment leaving the regulated area to verify that materials are contamination-free.
6. Decontaminate all materials that carry contamination with "decon" solutions before removing from regulated area.
7. Mark all equipment that can become re-contaminated during normal use. Tag or paint equipment to signify the potential for chemical contamination and the need for PPE. Secondary exposure sources:
8. Observe the flow of people entering and leaving regulated process areas.
9. Check water fountains, telephones, wash and change rooms, lunch and break rooms with "swypes" for contamination that may be transferred via workers’ hands, clothing or shoes.
10. Check office area floors and aisles leading out of regulated areas, doors, door knobs and handles, phones, copiers, pencils, and other equipment that may be contacted by contaminated PPE, clothing, or shoes.
11. Decontaminate all safety glasses, respirator face pieces, gloves, and other reusable personal equipment worn in the process area. Replace equipment that cannot be thoroughly decontaminated.
12. Check surfaces, tools and equipment in quality control labs that may carry contamination. Decontaminate all surfaces and materials that indicate the presence of contamination.
Source: Colormetric Laboratories, Inc.
*Swypes are surface contamination detectors made by Colormetric Laboratories. They have been evaluated by OSHA for use in exposure assessments and PPE training. Contact Colormetric at 847-696-3036.
Sidebar: Pointers for picking protective clothingKeep in mind these points from the National Institute for Occupational Safety & Health when choosing chemical protective clothing (CPC) to protect workers from dermal exposures: ·
- "Impervious" clothing does not exist. All commercially available CPC tested will allow some chemicals to permeate in relatively short times. ·
- All CPC is vapor resistant, which prevents evaporative cooling and increases skin temperature and moisture. Under these conditions, detecting a permeated chemical is difficult unless sensory effects such as itching, discoloration, or burning result. Even when CPC is removed, an exposure might not be recognized if an odor is not noticeable or the skin appearance has not changed. Furthermore, the warm, humid conditions under the CPC can increase the permeability of the skin. ·
- When the CPC being used has not been tested under the expected conditions, the CPC may fail to provide adequate protection. Wearers should observe the CPC during use and treat any noticeable change (e.g., color, stiffness, chemical odor inside) as a failure until proved otherwise by testing. If the work must continue, new CPC should be worn for a shorter exposure time, or CPC of a different generic material should be worn. ·
- The same thickness of a generic material, such as neoprene or nitrile, supplied by different manufacturers may provide significantly different levels of protection because of variations in the manufacturing processes or in the raw materials and additives used in processing. ·
- Most permeation data have been produced by testing the CPC material while in continuous contact with the chemical. This method of testing is considered the "worst case" condition that produces the quickest breakthrough time. Although it appears this breakthrough time could be safely increased if intermittent contact is expected, researchers have shown that, in some cases, breakthrough times for intermittent exposure are similar to continuous contact. Breakthrough times for intermittent exposure can be estimated during the testing of candidate CPC by using intermittent chemical contact with the candidate CPC to simulate expected use. ·
- Published permeation data of CPC tested against pure chemicals do not correlate with data for the same chemicals in mixtures, and cannot be used to reliably predict breakthrough times for mixtures. Unfortunately, chemical mixtures are usually encountered in the industrial setting. When data are not available for specific mixtures, use the worst-case data for any component of the mixture to select the candidate CPC. Source: NIOSH, 1990.