Thursday, March 13, 2008

Perchlorate in Our Food

On January 2, 2008, FDA published a study entitled "U.S. Food and Drug Administration's Total Diet Study: Dietary Intake of Perchlorate and Iodine" in the Journal of Exposure Science and Environmental Epidemiology. The study was designed to provide perchlorate and iodine intake averages from food for the entire U.S based on analytical results for perchlorate from FDA's TDS samples collected in FY 05/06 and for iodine from TDS samples collected in FY03/04.

Perchlorate - a major component in rocket fuel also forms naturally. In certain amounts it disrupts the thyroid by inhibiting the uptake of iodine which is an essential component of thyroid hormones. The thyroid hormones direct brain development and therefore, health concerns have focused on fetuses and young infants. Iodine deficiency during pregnancy can affect fetal and newborn development. The National Academy of Sciences (NAS) in 2005 recommended as a safe dose - 0.7 micrograms per kilogram of body weight per day, and EPA adopted this as its reference dose.

In the FDA study, the perchlorate levels were measured in 285 foods obtained from grocery stores and fast-food outlets in different parts of the U.S. between 2003 and 2006. To estimate exposure, they combined the analytical results with food consumption estimates. Drinking water was excluded from the survey. Numerous studies have found perchlorate in food, but this is the first to estimate exposure for the U.S. population. However, the survey does not provide information about the distribution of perchlorate exposures.

The results showed that:

for perchlorate:

The estimated lower bound to upper bound average perchlorate intakes by the 14 age-sex groups range from 0.08 to 0.39 micrograms per kilogram body weight per day (µg/kg bw/day), compared with the U.S. Environmental Protection Agency (EPA) Reference Dose (RfD) of 0.7 µg/kg bw/day. Children 2 years of age, with estimated average intakes ranging from 0.35 to 0.39 µg/kg bw/day, have the highest total perchlorate intake per kilogram body weight per day, but are below the RfD of 0.7 µg/kg bw/day recommended by the National Academy of Sciences and adopted by the U.S. Environmental Protection Agency. Total average intake ranges for infants 6-11 months, children 6, and children 10 years of age are estimated to be 0.26 to 0.29 µg/kg bw/day, 0.25 to 0.28 µg/kg bw/day, and 0.17 to 0.20 µg/kg bw/day, respectively. The estimated total average intakes by the other age-gender subgroups ranged from 0.08 to 0.14 µg/kg bw/day.

for iodine:

The estimated average iodine intakes by the 14 age-gender subgroups show a range from 138 to 353 µg/person/day. The estimated average iodine intakes for infants, 6-11 months exceeded their adequate intake (AI) of 135 µg/person/day. The estimated average iodine intakes by all other 13 children and adult age-gender subgroups exceeded their relevant estimated average requirements (EARs) of 65 µg/person/day for children 2 and 6 years, 73 µg/person/day for children 10 years, and 95 µg/person/day for the remaining 10 age-gender subgroups.

FDA does not recommend any changes to infants' and children's diets and eating habits based on current perchlorate data. FDA continues to recommend a healthy eating plan, consistent with the Dietary Guidelines for Americans. The adequate intake of iodine has previously been recognized as important for healthy thyroid function.

Perchlorate is found in water as well. FDA has not established a standard for perchlorate in bottled water, and the current bottled water regulations do not require bottled water manufacturers to test for perchlorate. EPA, the institution that regulates the tap water, has not yet determined whether a drinking water standard (i.e., a maximum contaminant level or MCL) is warranted for perchlorate. I wonder what the added exposure to perchlorate from food and water is and what the health effects of this are.

No comments: