# CRITERIA DOCUMENT: RECOMMENDATIONS FOR AN OCCUPATIONAL EXPOSURE STANDARD FOR TOLUENE DIISOCYANATE

# RECOMMENDATIONS FOR A TOLUENE DIISOCYANATE STANDARD
The
Administrative controls can also be used to reduce exposure to TDI.  does not exceed 100 times the time-weighted average for continuous work, or 100 times the ceiling for work of short duration, eg 20 minutes or less.
( Rubbers shall be decontaminated and ventilated after contamination.
Leather shoes which have been contaminated with TDI shall be decontaminated or disposed of.
Workers within 10 feet of spray operations, or at greater distances when there is a greater drift of spray, shall be protected with impervious clothing, gloves, and footwear in addition to a supplied air impervious hood.
(2) Chemical workers' goggles shall be worn where splashes are likely to occur. The two isomers are believed to have similar physiological properties.
 Their physical and chemical properties are very similar except that the 2,6 isomer has a lower freezing point.
 The 80% 2,4:20% 2,6 mixture represents better than 95% of industrial usage.
Properties of commercial samples of this mixture are listed in

# R-NCO + H20 yields RNH-COOH which yields R-NH2 + C02
The primary amine so produced will react further with excess TDI with the formation of a urea derivative: Probably because it reacts avidly with all proteins, its direct effects are, in accidental or occupational exposure of man, virtually confined to its reaction upon the surface membranes of the body.
Systemic absorption of TDI, with toxic effects upon internal organs, has not been reported in man, except in the special sense of the hypothetical immunologic involvement of the reticuloendothelial system in those subjects who become sensitized to TDI.
In the occupational exposure of man to TDI in the vapor or aerosol phase, its impact upon the respiratory tract is overwhelmingly the most important. Its topical effects upon other tissues will be briefly considered first. In a plant producing slabs of polyurethane foam by a continuous process air levels of TDI and the workers' health were studied for a period of 2-1/2 years.
 More than 1,000 air samples were analyzed. The extreme range of air level values at various sites and times was a reported 0.00 to 3.0 ppm. The range of average values for the various sites was given as 0.00 to 2.6 ppm. It is impossible to determine a time-weighted average level from the data published, but monthly average levels throughout the plant were reported to be in the 0.00 to 0.15 ppm range.
During the study period a total of 83 illnesses attributed to TDI required medical attention.  Twenty of the original cohort of workers had by 1969 been followed at 6-monthly intervals for a total of two years (five series of examinations).
 During the second year of follow-up the decline of FEV 1.0 had continued at a mean annual rate of 0.11 liters, which exceeds the predicted rate of decline due to aging alone. It is confirmed in this report  that acute daily changes in ventilatory capacity continued to occur in workers after two years and more continued exposure to TDI at low levels, that workers with respiratory symptoms showed a greater acute and cumulative response to TDI than asymptomatic workers, that there was a strong correlation between oneday change and cumulative effect, and that the effect of smoking does not seem important.  For the highly sensitized individual it is doubtful whether there is a measurable safe level for TDI below which that individual is completely safe from response.
Whether there is a measurable level below which no one will become sensitized de novo is not completely clear from the available evidence to date, although this is the intended basis for the TLV of 0.02 ppm
(1) Additional company analyses verify that air levels were high.
(2) The workers wore respirators, which probably indicates acute irritation.
(3) Some workers had been transferred after complaints.

# method.
[ The calibration instrument will be connected in sequence to the impinger unit which will be followed by the sampler pump. In this way, the calibration instrument will be at atmospheric pressure.
If the personal sampler pump is used, each pump must be calibrated separately.
If the burette is used, it should be set up so that the flow is toward the narrow end of the unit.
From these data, it can be seen that at all exposure levels of 0.01 ppm or higher, some cases of TDI toxicity occurred, but there were no cases at 0.007 or lower. At 0.009 ppm, there were no established cases, but one questionable one; there were several established cases at 0.008 ppm. It is concluded that the timeweighted average environmental limit should be below 0.01 ppm, and should be 0.005 ppm to ensure some margin of safety.