Environmental Project, 943 – Evaluation of health hazards by exposure to BAM (2,6-Dichlorobenzamide) and risk characterisation of drinking water exposure – 8 Risk characterisation, drinking water exposure

Evaluation of health hazards by exposure to BAM (2,6-Dichlorobenzamide) and risk characterisation of drinking water exposure

8 Risk characterisation, drinking water exposure

A NOAEL range of 2.5 – 6 mg/kg bw/day is selected for the human risk characterisation.

Intake of contaminated drinking water is the most relevant route of exposure to BAM.

An adult person weighing 70 kg drinks about 2 litres of water every day, i.e. 0.03 l/kg body weight (bw)/day. This is a default value, and it does not take into consideration that hot weather and high physical activity will increase the intake. For children in the age group 1 – 10 years, a daily water intake of 0.08 l/kg bw/day can be taken as a 95-percentile (U.S.Environmental Protection Agency, 1997).

An acute dietary risk of BAM is not considered relevant.

If the water contains 0.1 µg BAM/l, which is the administrative threshold limit in drinking water, the intake of 0.003 µg BAM/kg bw/day and 0.008 µg/kg bw/day for adults and children, respectively (see Tables 1 and 6). Exposure to the highest concentration detected in a recent study, 14 µg/l (Brüsch, 2002), corresponds to an intake of 0.42 µg BAM/kg bw/day and 1.12 µg/kg bw/day for adults and children, respectively. Exposure to the unusual and extremely high concentration detected in the period 1991 – 2001, 560 µg/l (Jørgensen, 2002), corresponds to an intake of 16.8 µg BAM/kg bw/day and 44.8 µg/kg bw/day for adults and children, respectively.

Table 6. Theoretical intake of BAM via drinking water

Water concentration of BAM	Theoretical intake of BAM for an adult person weighing 70 kg	Theoretical intake of BAM for 1 – 10 years old children
0.1 µg/l	0.003 µg/kg bw/day	0.008 µg/kg bw/day
1.0 µg/l	0.03 µg/kg bw/day	0.08 µg/kg bw/day
10.0 µg/l	0.30 µg/kg bw/day	0.80 µg/kg bw/day
14 µg/l	0.42 µg/kg bw/day	1.12 µg/kg bw/day
560 µg/l	16.8 µg/kg bw/day	44.8 µg/kg bw/day

The margin of safety (MOS) is calculated as:

MOS = NOAEL / BAM intake

Table 7. Margin of safety (MOS)

Water concentration of BAM	MOS an adult person weighing 70 kg	MOS for 1 – 10 years old children
0.1 µg/l	8.3 x 10⁵ – 2.0 x 10⁶	3.1 x 10⁵ – 7.5 x 10⁵
1.0 µg/l	8.3 x 10⁴ – 2.0 x 10⁵	3.1 x 10⁴ – 7.5 x 10⁴
10.0 µg/l	8.3 x 10³ – 2.0 x 10⁴	3.1 x 10³ – 7.5 x 10³
14 µg/l	6.0 x 10³ – 1.4 x 10⁴	2.2 x 10³ – 5.4 x 10³
560 µg/l	1.5 x 10² – 3.6 x 10²	55.8 – 134

The estimated MOS greatly exceeds 1000 in most cases.

When using the above risk characterisation and the MOS-calculation for risk management purposes several issues should be addressed.

Regarding the information given to people who have been exposed to contaminated wells, the above calculated MOS-values can be used to express concern/no concern in relation to intake in the past.

In relation to establishing a protection level and providing adequate information for the continued use of wells containing low residue levels, several health and policy related issues should be considered as well. When assessing the safety of different levels of the substances, the possibility of fluctuations in contamination levels as well as the possible occurrence of other contaminants that may follow together with the residues should be considered. Further, attention should be given to the policy concerning protection of the ground water as a drinking water resource and to the overall policy for a drinking water supply aiming at clean and unpolluted drinking water. Therefore, a possible maximum level of residues of BAM in drinking water should not be established as toxicologically acceptable levels but as levels that can be accepted based on overall considerations taking into account the overall policy, the necessity of sufficient drinking water supply and the protection of human health.