Skin Absorption of Contaminants In Water
by Elmer G. Heinrich
Reprinted from Wellness Lifestyle, January 1990
Several EPA surveys, taken during the last several years, indicate that both finished and ground water supplies throughout the United States have been contaminated with volatile organic compounds. The compounds and concentrations vary considerably by location but are generally highest in the industrialized areas east of the Mississippi River.
While contamination of surface waters is found more frequently, ground water degradation is of particular concern because of the high levels detected and because pollution of ground water is not reversible. There are no known natural cleansing processes associated with ground water movement in the Earth. Since about one half of the population relies on ground water for its daily water supply, this is a matter of concern for regulators. Acute and chronic effects have been demonstrated for most of these compounds, and several are suspected or known carcinogens. Others have shown mutagenic and teratogenic capacities.
Water and health regulators of today face complex problems in assessing the health hazards associated with contamination of drinking water supplies. Due to the general absences of federal drinking water standards for the volatile solvents commonly found in contaminated water, state and local authorities must decide whether to discontinue or restrict use of water supplies on a cases-by-case basis.
These decisions are heavily, if not exclusively, based on the recommendation of a toxicologist.
The methodology to calculate an acceptable level of a chemical in drinking water has been developed by the National Academy of Sciences and is incorporated in the Environmental Protection Agency's "suggested no adverse response level." These figures represent the highest level or dose of chemical compounds which produced no observed adverse side effect in chronic or sub-chronic tests with animals or humans, divided by the volume of water consumed by an average adult or child in order to calculate the acceptable concentration of a chemical in water measured in parts per million. One of the underlying assumptions here is that ingestion constitutes the chief route of exposure to the contaminant. Such an assumption disregards other routes of exposure such as skin absorption during bathing or swimming and inhalation of vapors while showering.
Other than occupation settings, little attention has been paid to skin absorption as a route of entry for volatile organic compounds and authorities and regulators have been primarily concerned with exposures via inhalation and ingestion. During the last 25 years, numerous investigators have explored the mechanism of epidermal barrier function in relation to solvents and solvent mixtures. Although a complex process, dermal uptake of compounds occurs mainly through passive defusion, involving selective mechanisms in various lipid and protein structures of the stratum corneum. According to the American Journal of Public Health, many investigators have reported on the toxicity and unexpectedly high penetration rates of volatile organics.
Numerous articles have been written with regard to skin absorption of disinfectants such as chlorine and volatile chemicals. One such article said, "Given the choice of drinking two liters of water contaminated with a volatile chemical at 7 parts per billion or showering for 15 minutes in the same water, the safer choice would be to drink the water." This conservative article said that from two to four times as much of the chemical can enter the body through skin absorption as through the intestines. One researcher says that, during a lifetime, 50 pounds of toxic wastes and pollutants can enter a body from drinking water and at least 450 pounds can enter the body through skin absorption.
The conditions under which exposure occurs and the specific characteristics of both the compounds and the people involved will each affect the rate and amount of absorption through the skin. Variables such as duration of exposure, type of skin exposed (chemical composition, vascularity, age, thickness), and amount of surface area exposed will influence absorption. Absorption intake is dependent upon skin hydration, water temperature, skin condition and regional variability. The epidermis of the hand represents a relatively greater barrier to penetration than many other parts of the body including the scalp, forehead, abdomen, postauricular areas, underarm, fossa cupitalis, and scrotum. According to the Journal of American Health, penetration through the scrotum is, in fact, estimated to be about 100% as compared to 8.6% for the forearm.
This information promotes speculation that most people have been approaching the water contaminant problem from the wrong angle. Obviously, the cumulative toxins one encounters from water is much more dramatic from bathing than from drinking.