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Environmental fate & pathways

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1,2-Dichloropropane undergoes reactions with hydroxyl radicals in the atmosphere. The calculated half-life of 1,2-dichloropropane due to this reaction is 34.9 days at based on an OH radical concentration of 5E5 OH/cm3, a 24 hour photoday, and an overall OH-rate constant of 4.6E-13 cm3/molecule-sec (298 K). Direct photolysis is not an important process.

Hydrolysis is not expected to be an important removal process for 1,2-dichloropropane. The half-life for this reaction in water (pH 6.9) is 283 months at 25 C (Milano et al., 1988). Hydrolysis products detected include 1-chloro-2-propanol and hydrochloric acid. The reaction is faster in seawater (pH 8.3) with a half-life of 60 months at 25 C.

Direct photolysis of 1,2-dichloropropane in water is not likely to be a significant removal process, since the molecule does not have chromophores which absorb wavelengths > 290 nm.

The results of biodegradation screening tests are variable. 1,2-Dichloropropane was not degraded in the Zahn-Wellens Test for inherent biodegradability. No degradation was also observed in the Modified MITI Test (301C). However, based on the supporting studies, 1,2-dichloropropane is susceptible to biodegradation under aerobic conditions when incubated with adapted cultures, particularly those containing microbial oxygenase enzymes with broad substrate specificity.

1,2-Dichloropropane was degraded in water and sediment by naturally occurring organisms under anaerobic conditions. Studies conducted with sediments from Red Cedar Creek demonstrated stochiometric conversion to propene after 4 months of incubation. Based on these results, the estimated half-life in surface sediments is 60 days at 25 C.

Half-lives for the dissapation of 1,2-dichloropropane in soils range from 41 to 69 days (average 52 days) at 15C. Based on the release rates of water extractable inorganic chloride, the complete degradation of 1,2-dichloropropane is slow.

Bioaccumulation of 1,2-dichloropropane does not appear to occur to a significant extent.  Measured bioconcentration factors (BCF) ranged from 0.5 to 6.9.

Soil adsorption coefficients (Koc) for 1,2-dichloropropane have been calculated using various equations based on the relationship between Koc and either water solubility or octanol-water partition coefficient. Reported values for Koc range from 46.9 to 299.14. The value estimated using a widely accepted quantitative structure activity relationship was taken as the key parameter (Koc = 60.3).

The Henry’s Law constant for 1,2-dichloropropane has been measured experimentally at different temperatures. The experimental values were generally consistent and in excellent agreement with calculated values. The measured value of 2.82 x 10e-3 atm-m3/mol at 25 C was taken as representative.