Formate is added to potable water on the International Space Station (ISS) in the process of adding minerals to pure water to make it more palatable. Highly pure water is supplemented with calcium and magnesium as the formate and acetate salts by adding 100 mL of a stock containing formate at 37.8 g/L to 44 L of pure (fuel-cell generated) water to yield about 86 mg/L (0.52 millimoles per liter [mmol/L]). Normally, the room-temperature water-dispensing port on the ISS is supplied with this U.S. formate-containing water, sometimes diluted with non-formate-containing water from other sources, while heated water (without formate) comes from Russian-supplied sources (either regenerated or natural water from Russia). If all the drinking water were formate-containing U.S. water, an astronaut would ingest 241 mg per day (d), at a consumption rate of 2.8 L/d of water.

TOXICOKINETICS AND METABOLISM

The distribution, metabolism, and elimination of formate have been studied in humans, nonhuman primates, rodents, and pigs.

Absorption

Gastrointestinal (GI) absorption of formate is almost total, as seen in cases of accidental and intentional self poisoning with formic acid solutions (Naik et al. 1980). No data were found on the rate of absorption of formate from the GI tract.

Distribution

Absorbed formate is distributed in the body water compartment, which in humans, is about 0.5 L per kilogram (kg) (Liesivuori and Savolainen 1991). No data were found on tissue-specific differences in the distribution of formate.

Metabolism

The major route of formate metabolism in the rat, monkey, and presumably in humans is oxidation to CO2 via the folate biochemical path-



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