p-cresol

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Principles of method if other than guideline:

Method: other (measured): critical review (data mostly measured according to methods developed by Atkinson and coworkers)

GLP compliance:

not specified

% Degr.:

50

Sampling time:

8 h

Test condition:

500000 OH radicals/ml

K[OH] = 4.7 [10E-11 cm3 molecule-1 s-1]
K[NO3] = 1.07 [10E-11 cm3 molecule-1 s-1]
K[O3] = 4.7 [10E-19 cm3 molecule-1 s-1]

Validity criteria fulfilled:

not specified

Conclusions:

The tropospheric half-life of p-cresol is approximately 8 h due to degradation by OH radicals with an average concentration of 500000 radicals/mL.

Executive summary:

The tropospheric half-life of p-cresol is approximately 8 h due to degradation by OH radicals with an average concentration of 500000 radicals/mL.

Reference 2

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Principles of method if other than guideline:

Method: other (measured)

GLP compliance:

not specified

Light spectrum: wavelength in nm:

ca. 450

Reference substance:

yes

Remarks:

1,3-butadiene or o-cresol 0.05-2.3 ppm

% Degr.:

50

Sampling time:

3.8 h

kOH = 2.21 x 10E-12 exp[(943+-449)/T] cm3 molec.-1 s-1 for a temperature range of 301-373 K

With a OH radical concentration of 1 000 000 molec cm-3 and a temperature of 301 K, the half-life is 3.8 h

Validity criteria fulfilled:

not specified

Conclusions:

A half-life of 3.8 h is calculated for p-cresol from smoke chamber experiments at different tempertures.

Executive summary:

A half-life of 3.8 h is calculated for p-cresol from smoke chamber experiments at different tempertures.

Description of key information

The tropospheric half-life of p-cresol is approximately 8 h due to degradation by OH radicals with an average concentration of 500000 radicals/mL .
An even shorter  half-life of 3.8 h at 23°C is calculated for p-cresol from smoke chamber experiment at different tempertures.

Key value for chemical safety assessment

Half-life in air:

8 h

Additional information

In the atmosphere, p-cresol will react with photochemically produced hydroxyl-radicals. In his critical review Atkinson recommended values for the reaction constant kOH at room temperature of 4.7 x 10-11 cm³ x molecule-per second. Based on a tropospheric OH radical concentration of 5 x 10⁵molecules per cm³ a corresponding half-life of 8.0 h can be calculated.

In an experiment the temperature dependency of the reaction constants in a smog chamber was determined. The calculated half-life is 3.8 h for p-cresol at 23°C.