Background
Organic solvents are a chemical class of compounds that are used routinely in commercial industries. They share a common structure (at least 1 carbon atom and 1 hydrogen atom), low molecular weight, lipophilicity, and volatility, and they exist in liquid form at room temperature. They may be grouped further into aliphatic-chain compounds, such as n -hexane, and as aromatic compounds with a 6-carbon ring, such as benzene or xylene. Aliphatics and aromatics may contain a substituted halogen element and may be referred to as halogenated hydrocarbons, such as perchloroethylene (PCE or PER), trichloroethylene (TCE), and carbon tetrachloride. Alcohols, ketones, glycols, esters, ethers, aldehydes, and pyridines are substitutions for a hydrogen group. Organic solvents are useful because they can dissolve oils, fats, resins, rubber, and plastics.
Organic solvents arose in the latter half of the 19th century from the coal-tar industry. Their application grew to be wide and diverse in both developed and developing countries. The introduction of chlorinated solvents in the 1920s led to reports of toxicity. Although solvents number in the thousands, only a few have been tested for neurotoxicity.
Workers in industries that use these agents may have occupational exposure, whereas other individuals may have environmental exposures if they live near industrial installations and/or have contact with contaminated water, soil, air, or food. Drinking water, shower water, ambient air, indoor air, and food, among other sources, are common routes of exposure to environmental toxins. [1] Inhalation, ingestion, and dermal absorption are also important mechanisms of toxic exposure. [2, 3, 4] Exposures often involve mixtures of solvents. Some of these incidents may occur deliberately when an individual recreationally inhales paints, glues, and other products; these exposures are described in more detail in the Medscape Reference article Inhalants.
The Occupational Safety and Health Administration (OSHA) regulates worker exposure. The National Institute for Occupational Safety and Health (NIOSH) and the American Congress of Governmental Industrial Hygienists (ACGIH) also publish standards for use in occupational settings in the United States.
Pathophysiology
Short-term, high-level exposures such as those frequently reported in case reports can result in acute reversible and irreversible health effects that involve the CNS and PNS. In population studies, intermediate- and long-term, low-level exposures have led to reversible and nonreversible subclinical and clinical abnormalities in the CNS and PNS. In some cases, these exposures were estimated to be below acceptable levels, as designated in regulations for workers. Neurophysiologic, neuropsychological, and neuroimaging diagnostic tools have been used to evaluate individuals and groups exposed to organic solvents.
Epidemiology
Frequency
United States
In 1987, NIOSH reported that 9.8 million workers were exposed to organic solvents in occupational settings. However, most occupational exposures involved solvent mixtures. Workers who use these agents include printers, paint manufacturers, painters, microelectronics workers, degreasers, dry cleaners, carpet layers, coating workers, gluers, dye workers, carpenters, anesthesia personnel, petrol filling workers, laboratory workers, inkers, and textile workers; others are those who work with polymers, pharmaceuticals, synthetic fabrics, agriculture products, refining, or in airplane refitting. Table 1 lists common sources of organic solvent exposures.
Table 1. Organic Solvents and Their Common Industrial Uses (Open Table in a new window)
Compound |
Industrial Uses |
Acetone |
Cleaning solvent |
Acrylamide |
Mining and tunneling, adhesives, waste treatment, ore processing |
Benzene |
Fuel, detergents, paint removers, manufacture of other solvents |
Carbon disulfide |
Viscose rayon, explosives, paints, preservatives, textiles, rubber cement, varnishes, electroplating |
Ethylene oxide (ETO) |
Instrument sterilization |
N- hexane |
Glues and vegetable extraction, components of naphtha, lacquers, metal cleaning compounds |
Hydrogen sulfide |
Sulfur chemical manufacturing, by-product of petroleum processing, decay of organic matter |
Methane |
Industrial settings |
Methyl mercaptan |
Odorant in natural gas and fuels |
Methyl-N- butyl ketone |
Many industrial uses |
Methylene chloride (dichloromethane) |
Solvent, refrigerant, propellant |
Organochlorine |
Insecticides |
Organophosphates |
Insecticides |
PCE |
Dry cleaning, degreaser, textile industry |
Styrene |
Fiberglass component, ship building |
Toluene |
Paint, fuel oil, cleaning agents, lacquers, paints and paint thinners |
1,1,1-Trichloroethane (methyl chloroform) |
Degreaser and propellant |
TCE |
Cleaning agent, paint component, decaffeination, rubber solvents, varnish |
Vinyl chloride |
Intermediate for polyvinylchloride resins for plastics, floor coverings, upholstery, appliances, packaging |
Xylene |
Paint, lacquers, varnishes, inks, dyes, adhesives, cements, fixative for pathologic specimens |
Environmental exposures to organic solvents occur. Solvents are also present in home products. According to NIOSH, 49 million tons of organic solvents were produced in the United States in 1984. Contamination affecting community water supplies, food additives, or household chemicals is an important source of exposure. Well-water sampling, both in the United States and abroad, has revealed quantities of chlorinated hydrocarbons and other solvents. Health effects secondary to these exposures have been described.
Estimating rates of occupational exposure is difficult because of a variety of factors. Worker exposures vary even within the same job, exposures vary during a workday, many routes of absorption are possible, personal protective equipment (PPE) is used inconsistently, and solvents are commonly used in various mixtures. For environmental exposures, similar challenges exist. Industrial hygienists and risk-assessment scientists work to overcome these challenges.
Age
Occupational exposures affect persons of working age. Environmental exposures affect persons of all ages.
Tables
Compound |
Industrial Uses |
Acetone |
Cleaning solvent |
Acrylamide |
Mining and tunneling, adhesives, waste treatment, ore processing |
Benzene |
Fuel, detergents, paint removers, manufacture of other solvents |
Carbon disulfide |
Viscose rayon, explosives, paints, preservatives, textiles, rubber cement, varnishes, electroplating |
Ethylene oxide (ETO) |
Instrument sterilization |
N- hexane |
Glues and vegetable extraction, components of naphtha, lacquers, metal cleaning compounds |
Hydrogen sulfide |
Sulfur chemical manufacturing, by-product of petroleum processing, decay of organic matter |
Methane |
Industrial settings |
Methyl mercaptan |
Odorant in natural gas and fuels |
Methyl-N- butyl ketone |
Many industrial uses |
Methylene chloride (dichloromethane) |
Solvent, refrigerant, propellant |
Organochlorine |
Insecticides |
Organophosphates |
Insecticides |
PCE |
Dry cleaning, degreaser, textile industry |
Styrene |
Fiberglass component, ship building |
Toluene |
Paint, fuel oil, cleaning agents, lacquers, paints and paint thinners |
1,1,1-Trichloroethane (methyl chloroform) |
Degreaser and propellant |
TCE |
Cleaning agent, paint component, decaffeination, rubber solvents, varnish |
Vinyl chloride |
Intermediate for polyvinylchloride resins for plastics, floor coverings, upholstery, appliances, packaging |
Xylene |
Paint, lacquers, varnishes, inks, dyes, adhesives, cements, fixative for pathologic specimens |
Compound |
Urine |
Blood |
Expired Air |
Acetone |
Acetone, formic acid 100 mg/L |
Acetone |
Acetone |
Benzene |
Total phenol 50 mg/g at the end of the shift, trans-trans- muconic acid |
Benzene |
Benzene before shift, 0.08 ppm; end exhaled, 0.12 ppm |
Carbon disulfide |
2-TTCA 5 mg/g* |
Carbon disulfide |
Carbon disulfide |
ETO |
None |
None |
None |
N- hexane |
2,5-hexanediol 5 mg/g at the end of the shift, 2-hexanol, total metabolites |
N- hexane |
N- hexane |
Hydrogen sulfide |
None |
None |
None |
Methane |
None |
None |
None |
Methyl mercaptan |
None |
None |
None |
Methanol |
Formic acid 80 mg/g at the start of the work week, methanol 15 mg/g at the end of the shift |
None |
Methanol |
Methyl-N- butyl ketone |
None |
2,5-hexane dione |
None |
Methylene chloride |
None |
MeCl2 |
MeCl2 |
Organochlorine |
None |
None |
None |
Organophosphates |
None |
None |
None |
PCE |
PCE, trichloroacetic acid |
PCE 1 mg/L |
PCE 10 ppm before the last shift of the week |
Styrene |
End of the shift: mandelic acid (MA) 800 mg, phenylglyoxylic acid (PGA) 240 mg/g) Before shift: MA 300 mg/g or PGA 100 mg/g |
Styrene 0.02 mg/L at the start of the shift, 0.55 mg/L at the end of the shift |
None |
Toluene |
Hippuric acid |
Toluene |
Toluene |
1,1,1-Trichlorethane (methyl chloroform) |
TCA 10 mg/L at the end of the work week; total trichloroethanol at the end of the shift and at the end of the work week, 30 mg/L |
Total trichloroethanol 1 mg/L |
Methyl chloroform 40 ppm before the last shift of the work week |
TCE |
TCE, TCA 100 mg/g at the end of the work week or TCA plus trichloroethanol 300 mg/g |
TCE at the end of the work week 4 mg/L |
TCE |
Vinyl chloride |
None |
None |
None |
Xylene |
Methylhippuric acid 1.5 g/g at the end of the shift |
Xylene |
Xylene |
* TTCA - 2-thiothiazolidine 4-carboxylic acid. |
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Compound |
ppm, mg/m,3 |
||
OSHA PEL as TWAs |
NIOSH REL as TWAs, IDLH |
ACGIH TLV, STEL |
|
Acetone |
1000 (2400) |
250 (590), 2500 |
750 (1780) ceiling, 1000 (2380) |
Acrylamide |
0.3 |
(0.03), 60 level for carcinogenicity |
None |
Benzene |
10, 25 ceiling, 50 for 10 min |
0.1, STEL 1, 500 |
10 (32) |
Carbon disulfide |
20, 30, 100 for 30 min |
1 (3), 10 STEL (30), 500 |
10 (31) |
ETO |
|
< 0.1, < 0.18, 5 ceiling, 800 |
1 (1.8) |
N- hexane |
500 (1800) |
50 (180), 1100 |
50 (176) |
Hydrogen sulfide |
20 ceiling, 50 for 10 min once only |
10 ceiling, (15) for 10 min, 100 |
None |
Methyl mercaptan |
10 ceiling (20) |
0.5 ceiling, (1) for 15 min, 150 |
None |
Methanol |
200 (260) |
200 (260), 250 STEL (325), 6000 |
262 (200), 328 (250) |
Methyl-n- butyl ketone |
100 (410) |
None |
5 (20) |
Methylene chloride |
25, 15 STEL for 15 min |
2300 level for carcinogenicity |
50 (174) ceiling |
Perchloroethylene |
100, 200 ceiling, 300 for 5 min in 3 h |
150 level for carcinogenicity |
25 (170), 100 (685) |
Styrene |
100, 200 ceiling, 600 for 5 min in 3 h |
50 (215), 100 ST (425), 700 |
50 (213), 100 (428) |
Toluene |
200, 300, 500 for 10 min |
100 (375), 150 STEL (560), 500 |
50 (188) |
1,1,1-Trichlorethane (methyl chloroform) |
350 (1900) |
Ceiling 350 (1900) for 15 min, 700 |
350 (1910), 450 (2460) |
Trichloroethylene |
100, 200 ceiling, 300 for 5 min in 2 h |
1000 level for carcinogenicity |
50 (269), 100 (1070) |
Vinyl chloride |
1, 5 for 15 min |
Not determined |
None |
Xylene |
100 (435) |
100 (435), 150 STEL (655) |
100 (434),150 (651) |
Abbreviations—ACGIH = American Congress of Governmental Industrial Hygienists, IDLH = Immediately dangerous to life or health; NIOSH = National Institute for Occupational Safety and Health, OSHA = Occupational Safety and Health Administration, PEL = permissible exposure limit, REL = recommended exposure limit; STEL = short-term exposure limit; TWA = time-weighted average. |
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