Skin notation

Nearly one-quarter of the substances in the TLV list are followed by the designation skin. This refers to potential significant contribution to the overall exposure by the cutaneous route, including mucous membranes and the eyes, usually by direct contact with the substance. This designation is intended to suggest appropriate measures for the prevention of cutaneous absorption. 

OCCUPATIONAL HEALTH AND SAFETY MANAGEMENT A PRACTICAL APPROACH 

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The toxicity of a substance is its capacity to cause injury once inside the body. The main modes of entry into the body by chemicals in industry are inhalation, ingestion and absorption through the skin. Gases, vapours, mists, dusts, fumes and aerosols can be inhaled and they can also affect the skin, eyes and mucous membranes. Ingestion is rare although possible as a result of poor personal hygiene, subconscious hand-to-mouth contact, or accidents. The skin can be affected directly by contact with the chemicals, even when intact, but its permeability to certain substances also offers a route into the body. Chemicals accorded a skin notation in the list of Occupational Exposure Limits (see Table 5.12) are listed in Table 5.2. Exposure may also arise via skin lesions. 

The Occupational Exposure Standards imposed for trichloroethylene are Maximum Exposure Limits of 100 ppm (8 hr TWA) and 150 ppm (15 minute reference period). A skin notation Sk is applicable because of the potential for skin absorption. Because of its volatility, trichloroethylene is not recommended for cold cleaning it is normally used in partially enclosed vapour degreasing equipment provided with local exhaust ventilation. 

The TLVs for airborne contaminants are based on the premise that although all chemical substances are toxic at some concentration for some period of time, a concentration exists for all substances from which no toxicity may be expected no matter how often the exposure is repeated. A similar premise holds for substances producing irritation, discomfort and nuisance. In using these limits, items such as excursion factors, ceiling values, "skin" notations, mixtures of substances, and inert material should be considered. These factors are discussed below. 

Skin notation The word skin included as part of an exposure limit. It is used for those substances for which absorption through the skin is considered to be a significant route of entry into the body. 

Group 3 not classifiable as to its carcinogenicity to humans Skin notation danger of outaneous absorption A4 not classifiable as a human carcinogen... 

The derived AEGLs are listed in Table 1-1. Because aniline is absorbed through the skin in quantities sufficient to induce systemic toxicity, a skin notation was added to the summary table. The reported odor threshold for aniline ranges from 0.012 to 10 ppm. Therefore, the odor of aniline will be noticeable by most individuals at the AEGL-1 concentrations. The odor is somewhat pungent but not necessarily unpleasant. 

The AEGL values and toxicity endpoints are summarized in Table 1-11. Because aniline is absorbed through the skin, a skin notation was added to the table of values. 

OSHA PEL Federal Permissible Exposure Limits based on a time-weighted average exposure over an 8-h period and 40-h work week. A [Skin] notation indicates that percutaneous absorption of the material is a potential hazard and may contribute to the overall exposure. 

Fiserova-Bergerova V, Pierce JT, Droz PO. 1990. Dermal absorption potential of industrial chemicals criteria for skin notation. Am J Ind Med 17 617-635. 

It should be noted that HCN can be absorbed through the skin. For this reason, ACGIH (1996) and NIOSH (1997) guidelines carry a skin notation. Drinker (1931) cites the case of three men protected with gas masks in an atmosphere of 2% (20,000 ppm) HCN. After 8 or 10 min the men felt symptoms of marked dizziness, weakness, and throbbing pulse. They left the chamber just before collapse. For several hours after the exposure they experienced weakness, high pulse rate, and headache. They were incapacitated for several days, followed by complete recovery. Based on exposure to several cyanide salts, the dermal LD50 in rabbits was calculated to be 6.7 mg CN/kg (Ballantyne 1983). 

The ACGIH has established a ceiling threshold limit value (TLV-C) of 0.1 ppm (0.8mg/m ) for occupational exposure to benzotrichloride with a skin notation and an A2 suspected human carcinogen designation. 

TWA, time-weighted average STEL, short-term exposure limit sk, skin notation... 

TWA, time-weighted average STEL, short-term exposure hmit A3, confirmed animal carcinogen with unknown relevance to humans sk, skin notation ° These countries follow the recommendations of the ACGIH threshold limit values Bulgaria, Colombia, Jordan, Republic of Korea, New Zealand, Singapore and Viet Nam... 

TWA, time-weighted average SUiL, short-term exposure limit MAK, maximum workplace concentration TLV, threshold limit value REL, recommended exposure hmit PEL, permissible exposure limit Ca, potential occupational carcinogen sk, skin notation... 

The American Conference of Governmental Industrial Hygienists (ACGIH) (1997) has recommended 31 mg/nr as the 8-h time-weighted average threshold limit value, with a skin notation, for occupational exposures to carbon tetrachloride in workplace air. Values of 10-65 mg/m have been used as standards or guidelines in other countries (International Labour Office, 1991). 

USA American Conference of Governmental Industrial Hygienists ceiling limit of 5 ppm, with a skin notation. 

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