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for eight hours to 200 ppm. With higher concentrations, definite symptoms of nervous
system impairment were observed. They suggest that the chief hazard of low level expo
sure to toluene may be an increased risk of accidents. Greenburg, et al. (2) reported
only slight evidence of intoxication in workers exposed to concentrations ranging from
100 to 1100 ppm of toluene.
In his discussion on the threshold limit of toluene, Gerarde (3) states that 200
ppm appears to be excessive, based on the work of von Oettingen (1)« Gerarde also
observes that in the USSR the threshold limit value for toluene is 25 ppm. An extensive
discussion of the toxic effect of toluene on rats is presented in a further publication
of Gerarde (4), but it cannot be said’that the threshold limit value is directly based
on consideration of these effects. Excellent reviews of toluene toxicity are also pre
sented in Patty (5) and Browning (6),
Recent industrial hygiene experience fails to support a limit below 200 ppm on
the basis of excessive irritation or other effects.
References:
■ ; nt
von Oettingen, et al.: Pub. Health Bull. No. 279 (1942).
Greenburq, L., Mayers, M.R., Heimann, H., Moskowitz, S.J.: Am. Med. Assn. 118,
573 (1942).
Gerarde, H.W.: Toxicology and Biochemistry of>Aromatic Hydrocarbons, Elsevier Pub.
Co., New York (1960) p. 148.
Gerarde, H.W.: Arch. Ind. Health 19, 403 (1959).
Patty, F.A.: Industrial hygiene and” Toxicology, Vol. II,.2nd Revised Ed., Inter
science Publishers, New York (1962), p. 1226-1229.
6. Browning, E.: Toxicity of Industrial Organic Solvents, Revised Ed.. Chemi cal Pub.
Co., Inc., New York (1953), pp. 46-55.
TOLUENE-2,4-DI ISOCYANATE (TDI)
Q
0.02 ppm (Approximately 0.14 mg/m )
Studies in animals by Zapp (1) have shown this isocyanate has a low oral toxicity
(approximate lethal dose5.8 g/kg), but a high toxicity by inhalation; 1 to 2 ppm for
30, six-hour exposures resulted in tracheobronchitis. The LCgg for three rodent species
for a four-hour exposure approximated 12 ppm according to Duncan, et al. (2); the ani
mals died of pulmonary edema and hemorrhage; effects on the liver, kidneys and gastroin
testinal tract also'occurred. Dermal effects occur. Repeated daily six-hour exposures*
to'0.1 ppm have been reported to cause chronic inflammation of the tracheo-bronchial
mucosa with fibrosa obliterans as the terminal lesion (3). A fever reaction in animals
following intravenous injection of 0.02 mg/kg has been reported by Scheel et al. (4).
The capacity of TDI to produce allergic sensitization of the respiratory tract of
man is its most serious toxicologic.action and which determines the magnitude of the
threshold limit value. A survey of plant experience made in 1960 by Elkins (5) at dif
ferent sites in six states showed cases of respiratory involvement from repeated ex
posure to TDI not only at or around 0.1 ppm (6,7) but considerably below 0.1 ppm. Thresh
old limits for minimizing respiratory effects suggested by the participants in the
survey were from 0.01 to 0.03 ppm A threshold limit of 0.02 ppm is recommended. It -
should be sufficiently low to prevent substantially all primary sensitization and to
minimize recurrent allergic attacks.
References:
1 Zapp, J.A.Jr.: Arch. Ind. Health 15, 324 (1957); Toxicity and Safe Handling of
Isocyanates, Mobay Chem. Co., Pittsburgh Pa. (undated).
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