Toxicological Evaluation and Limit Values for Nonylphenol, Nonylphenol Ethoxylates, Tricresyl, Phosphates and Benzoic Acid

8. TDI, health based limit values

8. TDI, health based limit values
8.1 TDI
8.2 Limit value in soil
8.3 Limit value in drinking water

o-TCP

The TDI of o-TCP is calculated based on the incident reported by Wang & Tao (1995) in which a LOAEL of 0.16 mg o-TCP/kg b.w./day was estimated for OPIDN in humans.

= 0.0003 mg/kg b.w./day

The safety factor SF_I is set to 1 as human data are used. The SF_II is set to 10 to protect the most sensitive individuals in the population. The SF_III is set to 50 as a LOAEL is used in stead of a NOAEL, because of the uncertainties in estimating a LOAEL from the data available, and because of the uncertainty on the content of mono-o-cresyl phosphates and di-o-cresyl phosphates (which are more potent than o-TCP in inducing OPIDN) in the contaminated flour.

If the TDI is calculated based either on the NOAEL for o-TCP of 2.5 mg/kg b.w./day for functional (ataxia) and morphological neuropathological changes observed in the 90-day oral study in hens (Prentice et al. 1983, Roberts et al. 1983), or on the NOAEL for o-TCP of 0.5 mg/kg b.w./day for delayed neurotoxicity observed in the 90-day dermal study in cats (Abou-Donia et al. 1986), TDIs of 0.005 mg/kg b.w./day or 0.001 mg/kg b.w./day, respectively, are obtained taking a safety factor of 500 into account. Thus the data obtained in animal studies are in concordance with the available human data.

TCP containing less than 0,1% o-TCP

The TDI for TCP will be calculated based on the 2-year dietary studies in rats and mice (NTP 1994), where a NOAEL of 7 mg TCP/kg b.w./day was estimated for ovarian interstitial cell hyperplasia in the rat and for effects on the liver in the mouse.

= 0.07 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 1 as well conducted 2-year studies in two animal species form the basis for the estimated NOAEL.

o-TCP

Based on the TDI of 0.0003 mg/kg b.w./day and assuming a daily ingestion of 0.2 g soil for a child weighing 10 kg (w_child), a limit value is calculated:

= 15 mg/kg soil

This limit value will also take into account the possibility for a child of developing acute toxic effects following a single ingestion of up to 10 g soil.

TCP containing less than 0,1% o-TCP

Based on the TDI of 0.07 mg/kg b.w./per day (for a single commercial product of TCP) and assuming a daily ingestion of 0.2 g soil for a child weighing 10 kg (w_child), a limit value is calculated:

The quality criteria for soil is going to cover all commercial products of TCP (containing less than 0.1% o-TCP) which consequently imply that different compositions of mixtures may occur and thus a possibility for mixtures containing more toxic isomers than the commercial product on which the TDI is based. Moreover, TCP are widespread in the environment having been detected in considerable amounts in sewage sludge. A further reduction factor (RF) is therefore set to 10.

= 350 mg/kg soil

8.3 Limit value in drinking water

o-TCP

Based on the TDI of 0.3 µg/kg b.w./day and assuming a daily intake of 2 litres of water for a person weighing 70 kg (w_adult), a limit is calculated:

= 11 µg/l

TCP containing less than 0,1% o-TCP

Based on the TDI of 70 µg/kg b.w./day and assuming a daily intake of 2 litres of water for a person weighing 70 kg (w_adult), a limit is calculated:

The quality criteria for drinking water is going to cover all commercial products of TCP (containing less than 0.1% o-TCP) which consequently imply that different compositions of mixtures may occur and thus a possibility for mixtures containing more toxic isomers than the commercial product on which the TDI is based. Moreover, TCP are widespread in the environment having been detected in considerable amounts in sewage sludge. A further reduction factor (RF) is therefore set to 10.

= 250 µg/l