1,4-dimethoxybenzene

Endpoint summary

Additional information

Short-term toxicity to fish:

Three studies of reliability 2 according to Klimisch were available and were chosen as key studies.

In the first 96-h acute toxicity study (Brooke et al., 1984), Pimephales promelas were exposed to Paradimethoxybenzene under flow through conditions. The 96-h LC50 was 117 mg a.i./L.

The sublethal effects were: affected fish became hypoactive, stopped schooling and lost equilibrium prior to death. 

In the second 96-h acute toxicity study (Broderius et al., 1983 and Veith et al., 1985), Pimephales promelas were exposed to Paradimethoxybenzene under flow through conditions. 

The 96-h LC50 was 117 mg a.i./L. There was no control mortality in tests with juveniles. 

In the third study (Clariant, 1988), fish Danio rerio were exposed to concentrations of Paradimethoxybenzene from 0 to 350 mg/L, under static conditions.

The 96-h LC50 was 127 mg/L based on mortality.

Based on the results of these studies, Paradimethoxybenzene should not be considered as harmful for fish, according to EC classification criteria.

Long-term toxicity to fish:

Only one study (Call et al., 1985) was available and was selected as key study.

In this subchronic toxicity study , eggs of Pimephales promelas were exposed to Paradimethoxybenzene at doses from 0 to 60.4 mg/L.

The NOEC-33d was 16.6 mg/L based on the hatchability, larval development, survival or growth in Pimephales promelas.

Acute toxicity on invertebrates:

Only two studies were available. One of them (RCC, 2006) quoted as reliability 1 according to Klimisch, was selected as key study; the other one of reliability 2 (Palla, 1983) was selected as supporting study.

In the key study (RCC, 2006), the acute toxicity of the test item Paradimethoxybenzene to Daphnia magna was determined in a 48 hour static test according to the EU Commission Directive 92/69/EEC, Part C.2 (1992) and the OECD Guideline for Testing of Chemicals, No. 202 (2004).
Due to the low water solubility of the test item, a supersaturated dispersion of the test item with a loading rate of 100 mg/L was prepared and filtered. The undiluted filtrate of the dispersion and dilutions 1:2, 1:4, 1:8, 1:16 and 1:32 were used as test media.
At the start of the test, the analytically measured test item concentrations in the analyzed test media (dilutions 1:4, 1:2 and the undiluted filtrate) amounted to 19, 40 and 78 mg/L, respectively. In these test media, the measured concentrations of Paradimethoxybenzene decreased to values of 15, 29 and 58 mg/L over 48 hours.
After 48 hours of exposure, no immobility of daphnids was observed in the control and at test item concentrations up to and including 17 mg/L. At the highest test item concentration of 68 mg/L, 80% of the daphnids were immobile.
The 48-hour EC50 was calculated to be 52 mg/L with 95% confidence limits of 49 and 55 mg/L. The 48-hour NOEC (highest concentration tested without toxic effects after 48 hours) of Paradimethoxybenzene were 17 mg/L. All biological results are based on the mean measured test item concentrations calculated as the geometric mean over all measurements per test concentration during the test period.

Algae studies:

Three studies were available, but only one (RCC, 2006) was of reliability 1 according to Klimisch ans was selected as key study.

The two other studies were of reliability 3, they were poorly described, so were not taken into account for the assessment.

In the key study, (RCC, 2006), the influence of the test item Paradimethoxybenzene on the growth of the freshwater green algal speciesPseudokirchneriella subcapitata was investigated in a 72-hour static test according to the EU Commission Directive 92/69/EEC, C.3 (1992), and the OECD Guideline 201 (2006).

Due to the low water solubility of the test item, a supersaturated dispersion of the test item with a loading rate of 100 mg/L was prepared and filtered. The undiluted filtrate of the stock dispersion and the dilutions 1:3.2,1:10,1:32,1:100 and 1:320 were used as test media.

At the start of the test, the measured test item concentrations in the analyzed test media samples (dilutions 1:32,1:10,1:3.2 and the undiluted filtrate) amounted to 2.68, 8.64, 26.9 and 87.4 mg/L. After 72 hours, the measured concentrations of Paradimethoxybenzene in these test media, incubated during the test period under the test conditions with algae decreased to 1.42, 5.36, 17.3 and 49.7 mg/L.

The 72-hour NOEC and LOEC for yield were determined to be 1.95 and 6.8, respectively.

The 72-hour NOEC and LOEC for growth rate were determined to be 6.8 and 21.6 mg/L, respectively.

The EC50 for yield and growth rate were determined to be 24.9 and 50.5 mg/L, respectively.

All biological results are based on the mean measured test item concentrations, calculated as the geometric mean over all measurements per test concentration during the test period.