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Administrative data

Workers - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
150 mg/m³
Most sensitive endpoint:
repeated dose toxicity
DNEL related information
Overall assessment factor (AF):
3
Modified dose descriptor starting point:
NOAEC
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
25 mg/kg bw/day
Most sensitive endpoint:
repeated dose toxicity
DNEL related information
Overall assessment factor (AF):
24
Modified dose descriptor starting point:
NOAEL
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available

Workers - Hazard for the eyes

Additional information - workers

The potential exposure to the test material indicates that long-term exposure DNELs need to be derived for workers and for the general population.  No acute toxicity was noted in any of the toxicological studies conducted.  Additionally, DNELs derived for chronic exposures are typically lower than those calculated for acute exposures and would therefore be protective of human for both the acute and chronic exposures. 

Dermal and inhalation are the relevant routes of exposure. Aspiration is a potential hazard, but a DNEL calculation is not appropriate for an aspiration hazard.

Workers are expected to have infrequent and short-term exposures; however, for calculation of the DNEL for REACH purposes it is assumed that workers have maximal repeated exposure for 8 hr/day for 5 day/wk.

Acute CNS Effects

 

Animals – In studies to define levels of acute CNS effects in rats, there were very minor effects at 5000 mg/m3 in rats exposed for 4 hours to 1,2,4 Trimethyl benzene (TMB). The no effect level was 1250 mg/m3. In rats exposed for 4 hours to a C9 aromatic solvent, minor but statistically significant effects were observed at 1000 mg/m3 with 200 mg/m3 as a no effect level (McKee et al. 2010). 

 

Humans – In human volunteer studies, Jarnberg et al.(1996) reported that no irritation or CNS effects were observed among volunteers exposed for 2 hours to each of the TMB isomers at 25 ppm. Similarly, Jones et al. (2006) stated that, among volunteers exposed for 4 hours to 25 ppm 1,3,5 TMB, “very little sensory irritation was reported and the exposure was well tolerated by all the volunteers. Note that 25 ppm is equivalent to approximately 125 mg/m3.

 

Thus the worker DNEL (inhalation, long term) of 150 mg/m3 is below no effect levels for acute CNS effects in animals and comparable to levels which produced no evidence of CNS effects or discomfort in humans.

 

References:

 

McKee, R. et al. (2010). Neurobehavioral effects of acute exposure to aromatic hydrocarbons. International Journal of Toxicology. In press.

 

Jarnberg, J. et al. (1996). Toxicokinetics of inhaled trimethylbenzenes in man. Toxicology and Applied Pharmacology 140:281-288.

 

Jones, K. et al. (2006). Biological monitoring for trimethyl benzene exposure. A human volunteer study and a practical example in the workplace. Annals of Occupational Hygiene 50:593-598.

Korsak, K. et al. (1998).  Toxic effects of acute inhalation exposure to 1-methylnaphthalene and 2-methylnaphthalene in experimental animals.  International Journal of Occupational Medicine and Environmental Health 11:335-342.

Carpenter, C. et al. (1975).  Petroleum hydrocarbon toxicity studies VII.  Animal and human response to vapors of “70 solvent. ” Toxicology and Applied Pharmacology 34:395-412.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
32 mg/m³
Most sensitive endpoint:
repeated dose toxicity
DNEL related information
Overall assessment factor (AF):
5
Modified dose descriptor starting point:
NOAEC
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
11 mg/kg bw/day
Most sensitive endpoint:
repeated dose toxicity
DNEL related information
Overall assessment factor (AF):
56
Modified dose descriptor starting point:
NOAEL
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available
Acute/short term exposure
Hazard assessment conclusion:
no-threshold effect and/or no dose-response information available

General Population - Hazard via oral route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
11 mg/kg bw/day
Most sensitive endpoint:
repeated dose toxicity
DNEL related information
Overall assessment factor (AF):
56
Modified dose descriptor starting point:
NOAEL
Acute/short term exposure
Hazard assessment conclusion:
exposure based waiving
DNEL related information

General Population - Hazard for the eyes

Additional information - General Population

The potential exposure to the test material indicates that long-term exposure DNELs need to be derived for general population. No acute toxicity was noted in any of the toxicological studies conducted. Additionally, DNELs derived for chronic exposures are typically lower than those calculated for acute exposures and would therefore be protective of human for both the acute and chronic exposures. 

 

Dermal and inhalation are the relevant routes of exposure. An oral DNEL was calculated for use in an indirect exposure assessment; the oral route is not expected to be a significant exposure route. Aspiration is a potential hazard, but a DNEL calculation is not appropriate for an aspiration hazard.

 

Consumers in the general population are expected to have infrequent and short-term exposures. However, for calculation of DNELs for REACH, it is assumed that consumers have a maximal repeated dose for 24 hr/day for 7 day/wk.