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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

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Environmental fate & pathways

Henry's Law constant

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Administrative data

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Reference
Endpoint:
Henry's law constant
Type of information:
other: review data
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
The Henry's law constant has been claculated from the ratio of vapour pressure and solubility.
GLP compliance:
no
H:
231.6 Pa m³/mol
H:
0.002 atm m³/mol
Executive summary:

The Henry constant was determined to be 231.6 Pm3/mol.

Description of key information

Due to the relatively high vapour pressure and low to moderate water solubilty, volatilisation from water to the atmosphere is an important distribution process for styrene. The Henry's law constant value of 232 Pa m³ / mol, calculated from vapour pressure and water solubility, indicates rapid volatilisation from surface waters. 
From the water surface, the substance will rapidly evaporate into the atmosphere

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
232
at the temperature of:
20 °C

Additional information

The volatilisation half-life of styrene from a body of water one metre deep, with a current velocity of 1 m/s and a wind velocity of 3 m/s is calculated to be about three hours. The U.S. EPA estimated that half-lives of styrene were three days in a pond and thirteen days in an oligotrophic lake (Environment Canada, 1993). Under laboratory conditions, Fu and Alexander (1992) found that styrene volatilised rapidly from shallow layers of lake water, 50% being lost in 1-3 hours. The half-life for volatilisation of styrene from soil surfaces was estimated to be approximately one minute with the rate of volatilisation decreasing with increasing depth (Environment Canada, 1993). Fu and Alexander (1992) found that volatilisation from soil was slower than from water, with 26% volatilisation from a 1.5 cm depth of soil in 31 days.