Background:

The main barrier between the surrounding environment and the interior anatomy of the human body is the very specialized organ called skin. The exposure of the skin to the various occupational and non-occupational chemicals, physical stressors, and biological agents may result in either a localized or systemic adverse health response. Millions of workers, from various industries, are affected with occupational skin diseases. Skin exposure assessment methodology is a little more complicated than other types of assessment, such as inhalation. Factors that complicate skin assessment include:

The skin exposure itself being variable and sporadic i.e., contact with surface, airborne deposition, splashes/mist, etc.

Skin absorption uncertainties

Difference between human skin and sampling substrate

Recovery of analyte from sampled skin

Methodologies are lacking for biologically relevant samples

Occupational exposure limits for comparison of sample results are lacking.

Some guidance for evaluating occupational skin exposure is offered from the OSHA Technical Manual (OTM) by recommending the use of the skin notation designation for chemicals in the ACGIH Threshold Limit Values section (Appendix B of the course text).

The EPA has published (2007) a summary of approaches for assessing skin exposure covering a wide range of situations including a) production of chemicals, b) exposures to consumer products, and c) contaminated water, soil, or sediment. The document lacks guidance with regards to the most appropriate approach to sampling.

S. A. Ness, in a publication called Dermal Sampling Techniques. In Surface and Dermal Monitoring for Toxic Exposures has recommended three sampling techniques for estimating skin contamination. There are several pathways the skin may become contaminated. By a liquid or solid aerosol, contact with contaminated surfaces, or by direct contact with the liquid or solid such as immersion or spillage. The three techniques for sampling include a) removal, b) interception, and c) in situ.

For the removal technique one would use one of the following procedures of wiping, washing, or tape stripping contaminates from the skin. This method assumes that the majority of the material on the skin is collected by the procedure. The efficiency of removal is affected by the pressure applied, type of sampling substrate, and accuracy in determining area of skin to sample. This method does not account for the portion that has volatilized or been accidently wiped off, portion washed off by sweating, or that portion that has permeated the skin before sample collection.

The interception technique utilizes a collection media such as gauzes, charcoal cloths, pads, patches or some other type of substrate placed directly on the skin or under outer clothing. This method is influenced by the actual variability in deposition rates of contaminants onto the body, the anatomical area of the body and duration of skin contact with foreign material, and permeation of a chemical over time.

The last technique is described as in situ and usually involves measuring a fluorescent tracer on the skin or clothing surface. The tracer may be added to the source of hazardous substance then by using an ultraviolet light probe the dispersion and pathway of the contaminant can be determined.

These dermal exposure labs demonstrate the various mechanisms of dermal exposure and discuss the various methods to assess dermal exposure. Additionally, various PPE will be assessed to evaluate the ability of PPE to prevent or reduce dermal exposure.

Materials:

Safety Glasses Gloves Uvitex Powder

Uvitex Liquid Spray Bottles Paper Towels

Vinegar Ammonia Cleaner UV light

pH paper Small Cup Water

Methods:

Safety glasses must be worn at all times.

Exercise #1 Interception Technique: pH paper and acid or base solution

By affixing pH paper to the hand before donning glove, the pH paper will act as a breakthrough indicator. It is recommended that the indicators be placed on the thumb, middle finger, back of hand and palm as these represent the areas of most frequent contact and glove abrasion.

To determine user safe time for the particular glove in question, follow this procedure.

Affix pH paper strips with tape to the recommended parts of the hand. Be careful not to cover large area of the pH paper with tape.

Don a glove on the hand to be evaluated

After performing Exercise #2, remove the glove.

Remove the pH paper and dip each strip into a cup of tap water. Lay the strips out on a clean area of the table and observe the color.

Record results in table 7.1 below.

Table 7.1

Location	Contamination Indicated (Y/N)	Comments

Exercise # 2 Removal Technique: Surface Wipe

A. Surface swipe indicators for contamination detection

Lightly spray the area or item (workbench, tool, control knob) with Vinegar.

Wait at least 30 seconds, and then wipe the surface dry with paper towel.

Wipe a piece of pH paper across the surface.

Dip pH paper into clean cup of water. The pH paper will change colors indicating the presence or absence of contaminate at point of contact. Contaminated parts will be yellow or red and non-contact and uncontaminated parts will turn green.

Note the extent of contamination in table 7.2 below.

Clean area with water and paper towel to remove contamination.

Re-check the area with a surface swipe indicator or pH paper to verify decontamination is complete.

Note the extent of contamination in table 7.2 below.

If contamination remains, repeat cleaning with water and checking for contamination.

Note any additional results in table below.

Table 7.2

Condition	Contamination Indicated (Y/N)	Comments

B. Skin swipe indicators for contamination detection on the non-gloved hand

Fill a small cup with tap water.

Wipe the skin of the palm on the non-gloved hand with the pH paper.

Dip the pH paper in the cup.

Lay the pH paper on the table in a clean location and observe the color.

Record results in table 7.3 below

Repeat process wiping the back of the non-gloved hand

Record results in table 7.3 below.

Table 7.3

Location	Contamination Indicated (Y/N)	Comments