m-Cresol - ipcs inchem

OECD SIDS
m- / p-CRESOL
The most sensitive fish species in acute toxicity tests belong to the salmonids. Howland (1969)
conducted static tests on the toxicity of m-cresol to three trout species and of p-cresol to 9 fish
species. Among the tests with m-cresol Salvelinus fontinalis was most sensitive exhibiting a LC50
of 7.6 mg/l, while with p-cresol as the test substance the lowest LC50 was found for Salmo trutta
(4.4 mg/l).
The effect values from tests on m- and p-cresols indicate toxicity in the same order of magnitude,
with p-cresol being slightly more toxic.
A chronic toxicity test (early life stage) with P. promelas was conducted with p-cresol over a period
of 32 days. A NOEC of 1.35 mg/l was obtained. This is a nominal concentration (Barron and
Adelman 1984). It has to be regarded that Pimephales promelas was not the fish species being most
sensitive in short-term tests.
Invertebrates
The acute toxicity of m-cresol to Daphnia magna was determined in a static immobilization test
after an exposure period of 24 h. Duplicate samples with each 10 individuals of 24 h old daphnids
were exposed to the test solutions. Analytical control was not performed. The nominal EC50 was
reported to be 25 mg/l (graphically determined) (Bringmann and Kühn 1982).
A comparable test was conducted with p-cresol. Kühn et al. (1988, 1989a) exposed each 20
daphnids in 4 replicates to p-cresol, the nominal EC50 was graphically determined to 4.9 mg/l.
The 3 valid test results, available for the short-term toxicity of m- and p-cresol on Daphnia magna,
allow a comparison of the acute toxicity of both substances on this species. The results demonstrate
a similar toxicity of both isomers.
Long-term tests to invertebrates are only available for p-cresol. In a semi-static test with Daphnia
magna, each 20 individuals (24 h old) in 4 replicates were exposed to p-cresol in a concentration
range of 0.003 - 10 mg/l. The test solutions were renewed 3 times per week, their stability was
controlled by analytical monitoring. After 21 days of exposure a NOEC of 1 mg/l was determined
(Kühn et al. 1988, 1989a).
Aquatic Plants
The cell multiplication inhibition of p-cresol on the alga Scenedesmus subspicatus was tested by
Kühn and Pattard (1990). The algae were exposed to concentrations between 0.8 and 100 mg/l.
Analytical control was not performed. Based on nominal concentrations a 48 h-EC 50 of 21 mg/l and
an EC 10 of 4.6 mg/l (both related to growth rate) were determined.
In a study with macrophytes (Nobel 1983) NOEC-values for the endpoint photosynthesis (oxygen
production) of 0.22 mg/l to 1.08 mg/l for m-cresol and < 0.22 mg/l to 1.08 mg/l for p-cresol are
reported and provide a hint towards higher sensitivity of macrophytes to cresols. However, as no
information is given about substance application, test design (no. of plants per vessel and
replication) and control performance, the study is considered invalid and is not used for the PNEC
derivation.
UNEP PUBLICATIONS 37