Exposure response function for nitrate and iMetHb

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Scope

To define the exposure response factor for nitrate exposure from drinking water causing iMetHb

European countries
Infants < 6 months of age
Oral exposure from drinking water via baby food formula or drinking water.

Definition

Causality

NA

Data

Accoding to US EPA IRIS (Integrated Risk Information System) NOAEL for nitrate is 10 mg nitrate-nitrogen/L (1.6 mg/kg/day) and LOAEL is 11-20 mg nitrate-nitrogen/L (1.8-3.2 mg/kg/day). Conversion Factor for nitrate-nitrogen is expressed as the amount of nitrogen within the nitrite molecule commonly shown as mg nitrate-nitrogen/L (1 mg nitrate-nitrogen = 4.4 mg nitrate. The oral Reference Dose (RfD), which is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis, is 1.6E+0 mg/kg/day. This results in early clinical signs of methemoglobinemia in excess of 10% (0-3 months old infants formula). U.S. EPA has evaluated the noncancer oral data for nitrate and derived a reference dose (RfD) of 1.6 mg/kg-day with 10 % of risk to MetHb.

http://www.epa.gov/NCEA/iris/subst/0076.htm

The exposure response slope was calculated from the following equation:

1-e ^(x*1.6)= 0.1 x = 0.06585

Formula

Unit

mg/kg/d / mg/l

Result

Slope of exposure response function for nitrate and iMet Hb= 0.06585