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

8. TDI, limit values

A NOAEL of 15 mg/kg b.w./day is used as the basis for the TDI calculation (see above).

= 0.015 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 to account for the severity of the effects of formaldehyde (indications of carcinogenic effects at higher dose levels).

Allocation

The general population is predominantly exposed to formaldehyde from food items. Therefore, only 10% of the oral TDI is allocated to ingestion of soil and 10% to drinking water.

Ingestion

Based on the TDI of 0.015 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:

= 75 mg/kg soil

Dermal contact

Dermal contact to soil polluted with formaldehyde may theoretically also be critical for formaldehyde sensitised people. However, a level of 75 mg/kg soil is considered to protect against skin reactions, as a NOAEL of 80 mg/kg has been found in clinical testing with formaldehyde solutions in sensitised people.

Based on the TDI of 15 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:

= 53 mg/l

8.4 Limit value in air

A limit value for acute exposure can be calculated based on an overall no effect level for irritation of 0.1 mg/m³ in the general population:

= 0.01 mg/m³

The safety factor SF_I is set to 1 as human data is used. The SF_II is set to 10 to protect the most sensitive individuals in the population. The SF_III is set to 1, as a NOAEL is used.

A limit value for long term exposure is based on the limit value for acute exposure as mechanistic data from animal experiments strongly suggest that a linkage exists between irritation and carcinogenic effects from long term exposure. Therefore, to account for remaining uncertainties regarding effects from long term exposure and to consider the severity of the effects a limit value of 0.001 mg/m³ as an average exposure level can be calculated. In this calculation SF_III is set to 10.