Toxicological evaluation and limit values for Methyl-tertiary-butyl ether (MTBE), Formaldehyde, Glutaraldehyde, Furfural

8. TDI, health based limit values

0,1 mg/kg b.w./day

The safety factor SF_I is set to 10 assuming that humans are more sensitive than animals. The SF_II is set to 10 to protect the most sensitive individuals in the population. The SF_III is set to 10 because the NOAEL was established on a 90-day study and to consider the severity of the effects (cancer) that may follow exposure to a toxic level.

Allocation

The general population is considered predominantly to be exposed to MTBE from air. Therefore, only 10% of the TDI is allocated to ingestion of soil and drinking water, respectively.

Based on the TDI of 0.1 mg/kg b.w. per day and assuming a daily ingestion of 0.2 g soil for a child weighing 10 kg (w_child), a limit value is calculated:

= 500 mg/kg soil

Such a value seems unrealistic high due to the odour potency of the substance, therefore a limit value for soil should rather be based on the evaporation of MTBE from the soil.

Based on the TDI of 100 mg/kg b.w. per day and assuming a daily ingestion of 2 litres of drinking water for an adult weighing 70 kg (w_adult), a limit value is calculated:

= 350 mg/l

Such a limit value for water seems unrealistic high due to the odour potency of the substance, therefore, a limit value for drinking water

should be based on the odour detection limit in water.

8.4 Limit value in air

= 0.26 mg/m³

The safety factor SF_I is set to 10 assuming that humans are more sensitive than animals. The SF_II is set to 10 to protect the most sensitive individuals in the population. The SF_III is set to 10 because the severity of the effect (cancer) that may follow the toxic effects.

This value is just above the experimental 50% detection odour limit for humans. Therefore, a limit value for MTBE in air should be based on the odour detection limit.