Aromatic hydrocarbons, C9-12, benzene distn.

Phototransformation in water

Administrative data

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

N/A

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data is from several peer reviewed sources.

Data source

Reference

Reference 1

Reference Type:

other: Computer model

Title:

Unnamed

Year:

1999

Reference 2

Reference Type:

review article or handbook

Title:

Unnamed

Year:

1982

Reference 3

Reference Type:

publication

Title:

Unnamed

Year:

1977

Reference 4

Reference Type:

review article or handbook

Title:

Unnamed

Year:

1977

Materials and methods

Study type:

other: Technical discussion

Principles of method if other than guideline:

Technical discussion

Test material

Test material information

Constituent 1

Reference substance name:

Hydrocarbons, C9, aromatics

EC Number:

918-668-5

IUPAC Name:

Hydrocarbons, C9, aromatics

Results and discussion

Preliminary study:

See discussion below

Applicant's summary and conclusion

Conclusions:

The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption
of light in the ultra violet (UV)-visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone
layer prevents UV light of less than 290 nm from reaching the earth's surface. Therefore, only light at wavelengths between 290 and 750 nm can
result in photochemical transformations in the environment. A conservative approach to estimating a photochemical degradation rate is to assume
that degradation will occur in proportion to the amount of light wavelengths >290 nm absorbed by the molecule. Aromatic hydrocarbons contain
molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, these substances will not
undergo direct photolysis and this fate process will not contribute to a measurable degradative loss of these substances from the environment.

Executive summary:

The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption of light in the ultra violet (UV) -visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone layer prevents UV light of less than 290 nm from reaching the earth's surface. Therefore, only light at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment.

A conservative approach to estimating a photochemical degradation rate is to assume that degradation will occur in proportion to the amount of light wavelengths >290 nm absorbed by the molecule. This substance contains hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, this substance does not have the potential to undergo photolysis in water and soil, and this fate process will not contribute to a measurable degradative loss of this substance from the environment.