When it comes to hazardous chemical exposures, airborne exposures get the lion’s share of the attention. The vast majority of permissible exposure limits are airborne exposure limits, and there are many options for characterizing airborne concentrations of chemicals. Instant-read air monitors, colorimetric tubes, and personal sampling pumps can all help you determine just how much of a given contaminant is in the air and how much your workers are breathing.
Dermal exposures are more difficult to characterize and monitor, and there is less guidance available for employers to determine which dermal exposures are more or less dangerous. One of the most complete available resources is the list of skin designations published by the National Institute for Occupational Safety and Health (NIOSH), which is included in the NIOSH Pocket Guide to Chemical Hazards. When it was first published in 1988, this list included 142 chemicals. But the “skin” designation provided only limited information for users; in particular, it was given only to chemicals that were known to absorb through the skin in concentrations sufficient to cause systemic toxic effects.
In July 2009, NIOSH updated its own Current Intelligence Bulletin 61, A Strategy for Assigning New NIOSH Skin Notations to account for and provide information on the different hazards posed by dermal exposure to chemicals, including corrosive and irritant effects, and allergic or sensitizing effects.
Getting Under the Skin
The skin is the body’s largest organ, and it is the body’s first line of defense against substances and exposures coming from the outside—including everything from sunlight and ionizing radiation to water, dust, and hazardous chemicals. The degree of protection that the skin provides varies with the type and duration of exposure—for example, exposure to the sun when it is most intense will result in sunburn.
A chemical’s health effects resulting from skin contact can be classified as:
- Systemic toxicity. Some toxic chemicals can be absorbed through the skin in sufficient amounts to cause systemic toxic effects.
- Direct effects on the skin. Some chemical exposures affect the skin only at the point of contact, resulting in a localized reaction that does not involve the immune system. These chemicals are irritants, corrosives, chemicals that disrupt skin barrier integrity, and those that affect skin pigmentation.
- Immune-mediated reactions. Skin exposures can cause immune system responses, including allergic and sensitized reactions like allergic contact dermatitis. These effects may cause immune responses in other systems, as when a skin exposure causes a sensitivity that affects not just the skin but also the respiratory tract, leading to respiratory sensitivity or occupational asthma.
Any of the three can result in a “skin” notation being added to the chemical’s listing in the NIOSH Pocket Guide to Chemical Hazards. In order to provide more detailed information than what is available in the Pocket Guide, NIOSH also publishes a Skin Notation Profile for each substance that is given a skin notation.
The type of damage that can occur as a result of skin exposure will affect the protective measures that are needed, so NIOSH further delineates its skin notations to indicate the specific effects of exposure. These notations and subnotations are indicated in the Pocket Guide using abbreviations: notations follow a colon; subnotations are in parentheses—thus, SK:DIR(IRR) designates a dermal hazard that causes direct damage to the skin as an irritant.
The notations are:
- SK:SYS—Systemic effects
- SK:SYS (FATAL)—Extremely toxic chemicals whose systemic effects may be life-threatening following a skin exposure
- SK:DIR—Direct effects
- SK:DIR (IRR)—Potential irritants
- SK:DIR (COR)—Corrosive chemicals
- SEN—Sensitizing effects
There is also a notation, ID(SK), that indicates that the chemical was reviewed, but insufficient data were available at the time of review to evaluate the health hazards of dermal exposures to the chemical. Another notation, ND, indicates that the chemical has not been evaluated for its health hazards via the dermal route of exposure.
As NIOSH evaluates chemicals under its new system, it adds or revises the notations. Tomorrow we’ll look at nine chemicals with new or newly updated skin notations as of August 2017.