Physical exposures, occupational

M. Nonchemical physical exposures in the workplace are important because they can cause systemic effects that mimic chemical toxidromes. The most important example is heat stress, which is a major occupational health issue. Other relevant nonchemioal, work-related physical exposure types include ionizing radiation, nonionizing radiation (such as ultraviolet, infrared, and microwave exposure), and increased barometric pressure (eg, among caisson workers). Except for extremes of exposure, the adverse effects of these physical factors are generally associated with chronic conditions. 

Basic information on the toxicity of many of the most commonly encountered and tox-icologically significant industrial chemicals is provided in Table IV-4. The table Is Intended to expedite the recognition of potentially hazardous exposure situations and therefore provides infomiation such as vapor pressures, warning properties, physical appearance, occupational exposure standards and guidelines, and hazard classification codes, which may also be useful in the assessment of an exposure situation. Table IV-4 is divided into 3 sections health hazards, exposure guidelines, and comments. To use the table correctly, it is important to understand the scope and limitations of the information it provides. 

Occupational and environmental medicine is a branch of medical practice specializing in disease and illness related to work and environmental exposures. Occupational health physicians diagnose and treat diseases and illness that may arise from work and exposure to hazardous environments. Such exposure may be a contributory factor in other diseases. Treatment may include various physical and occupational therapies to allow a return to work. Occupational health physicians also promote healthy workplaces and deal with workplace stresses. The professional organization in the United State is the American College of Occupational and Environmental Medicine (ACOEM). 

For each kind of chemical and physical exposure, there are accepted procedures and instmments for making measurements. This book cannot provide full details on current instruments and measurement procedures. Readers should refer to current publications and regulations about accepted practices. Readers can also seek assistance from occupational safety and health or industrial hygiene professionals. 

Evaluations of occupational exposure to physical agents such as noise, radiation or heat, biological agents, and multiple chemical agents are similar to the process for single chemical substances but have some key differences. 

ACGIH maintains annual editions of the TLVs and BEIs which are used worldwide as a guide for evaluation and control of workplace exposures to chemical substances and physical agents. Threshold Limit Value (TLV ) occupational exposure guidelines are recommended for more than 700 chemical substances and physical agents. There are more than 50 Biological Exposure Indices (BEIs ) that cover more than 80 chemical substances. 

The specific values of the physical and biological characteristics such as breathing patterns for occupational exposure and active and resting patterns for environmental exposure are given in the footnotes to the Tables. A few remarks should be made concerning the parameters used which affect the dose calculation significantly. 

Subsequently, individual data on exposure are converted to dose by using conversion factors (OECD/NEA, 1983). The choice of the appropriate numerical value depends on physiological parameters (e.g. respiratory minute volume) as well as physical characteristics of the inhaled aerosol (e.g. particle size). Mean values range typically from about 5 mSv/WLM (non-occupational exposure) to about 10 mSv/WLM (occupational exposure). 

In a study conducted at the Lovelace Inhalation Toxicology Research Institute (ITR1), rats were exposed for up to 30 months, 7 h/day, 5 days/wk, to diesel exhaust containing 0, 0.35, 3.5, or 7.1 mg soot/m3 of air. The diesel engine exhaust was generated as indicated in the section of this paperon "Physical/Chemical Characteristics of Diesel Soot." The lowest exposure concentration, 0.35 mg soot/m3, is directly relevant to some occupational exposures and is 10 to 100 times higher than any current or anticipated environmental exposures. Observations of the animals were made at 6-mo intervals and included measures of dosimetry (mg soot/g lung),... 

During occupational exposure, respiratory absorption of soluble and insoluble nickel compounds is the major route of entry, with gastrointestinal absorption secondary (WHO 1991). Inhalation exposure studies of nickel in humans and test animals show that nickel localizes in the lungs, with much lower levels in liver and kidneys (USPHS 1993). About half the inhaled nickel is deposited on bronchial mucosa and swept upward in mucous to be swallowed about 25% of the inhaled nickel is deposited in the pulmonary parenchyma (NAS 1975). The relative amount of inhaled nickel absorbed from the pulmonary tract is dependent on the chemical and physical properties of the nickel compound (USEPA 1986). Pulmonary absorption into the blood is greatest for nickel carbonyl vapor about half the inhaled amount is absorbed (USEPA 1980). Nickel in particulate matter is absorbed from the pulmonary tract to a lesser degree than nickel carbonyl however, smaller particles are absorbed more readily than larger ones (USEPA 1980). Large nickel particles (>2 pm in diameter) are deposited in the upper respiratory tract smaller particles tend to enter the lower respiratory tract. In humans, 35% of the inhaled nickel is absorbed into the blood from the respiratory tract the remainder is either swallowed or expectorated. Soluble nickel compounds... 

THRESHOLD LIMIT VALUE DS2 is made of two major components (EGME DETA) with different toxicities and physical properties. The TLV of the mixture (calculated) is 5.2 mg/m3 as an 8-hour time weighted average (TWA). To date the Occupational Safety and Health Administration (OSH A) has not promulgated a permissible exposure limit for DS2 nor has the value proposed been officially adopted as a part of a special occupational safety and health standard for DS2 according to DOD 6055.1. 

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