Perchlorate Pump: Molecule draws contaminant into breast milk

Sarah C. Williams Science News Week of Dec. 8, 2007; Vol. 172, No. 23 , p. 358

A molecular pump designed to transport iodine also concentrates the pollutant perchlorate in breast milk, scientists have shown. The result is higher levels of the chemical in breast milk than in other parts of the body, with implications for the amount of perchlorate that pregnant and lactating women can safely ingest.

For the past decade, scientists have debated the health effects of perchlorate, which leaches into groundwater around explosives manufacturing plants. The contaminant was found in some states' drinking water in the mid-1990s. Since then, perchlorate has also turned up in produce grown with contaminated water, and scientists and policy makers have reached no consensus on what levels of the chemical are safe in humans.

Toxic Controversy: Perchlorate found in milk, but risk is debated

Ben Harder Science News Week of Oct. 11, 2003; Vol. 164, No. 15 , p. 230

Researchers in Texas have detected the chemical perchlorate in milk, crops, and a significant portion of the state's groundwater. However, it's unclear how much exposure people face through food or water, and a scientific gathering has just produced a statement downplaying perchlorate's biological effects.

Perchlorate is known to occur naturally only in parts of Chile (SN: 10/16/99, p. 245: http://www.sciencenews.org/sn_arc99/10_16_99/fob3.htm). Most perchlorate in the environment is thought to come from Chilean fertilizer ingredients or from solid rocket fuel, which contains synthetic perchlorate.

The compound can affect the thyroid gland because it inhibits the tissue's uptake of iodine from the blood. Health concerns focus on pregnant women and children, whose development could be disrupted by decreases in thyroid hormone due to insufficient iodine uptake.

So far, only California has established a preliminary drinking-water standard for perchlorate—4 micrograms per liter. Last year, the Environmental Protection Agency proposed a more stringent standard of 1 µg/l, but the Department of Defense challenged the underlying risk assessment, which is now being reviewed. Other groups argue that amounts dozens of times EPA's proposed limit would still be safe. None of these proposals accounts for exposure to perchlorate through food.