Perchlorate in Japanese dairy milk
Big in Japan—a new study confirms that perchlorate is ubiquitous.
Cow’s milk in Japan contains more perchlorate than U.S. milk, even though Japan lacks an extensive military–industrial base, according to new research published today on ES&T’s Research ASAP website (DOI: 10.1021/es061429e). The study could put an end to the notion that widespread low-level perchlorate contamination comes mainly from military sources.
Analytical chemist Purnendu “Sandy” Dasgupta, formerly at Texas Tech University and now at the University of Texas, Arlington, and his colleagues in Japan obtained 54 samples of mostly whole milk from 48 different locations throughout Japan. The perchlorate concentrations averaged 9.39 parts per billion (ppb) and ranged from 5.47 to 16.40 ppb. A 2004 U.S. Food and Drug Administration study reported concentrations of 1.9–11.3 ppb in U.S. milk, with an average of 5.74 ppb.
The results confirm that perchlorate is ubiquitous, says Dasgupta. “Many countries may have greater perchlorate contamination than the U.S., regardless of the fact they did not have a great deal of military–industrial use,” he adds. In the U.S., the historic use of Chilean nitrate fertilizer probably accounts for more low-level perchlorate contamination than military industrial sources do, according to a recent Dasgupta paper.
The authors suggest that natural sources and perchlorate produced for fireworks may be responsible for the higher levels in Japan. Relative to the U.S., more naturally formed perchlorate likely rains down on Japan. The country gets more rainfall than the U.S., and perchlorate forms more readily in coastal areas where sea-salt aerosols can react with lightning or ozone. At the same time, perchlorate usage in Japan is greater in comparison to its size (more perchlorate per hectare).
But some researchers question the paper’s significance. “We already know that perchlorate is nearly everywhere. It is not clear where it all is coming from, and this paper doesn’t answer that question,” says one thyroid scientist. The authors should have measured perchlorate in multiple foods and drinks, and they should have measured iodine in all the milk samples, the scientist adds.
“With Japan’s excellent iodine nutrition, it is unlikely to see the association between perchlorate exposure and perturbation of thyroid hormones observed in the U.S.,” Dasgupta says, noting that international health organizations consider Japan to have an excessive iodine intake. The U.S. Centers for Disease Control and Prevention recently reported an association between elevated levels of perchlorate in urine and perturbed thyroid hormones in U.S. women with low levels of iodine nutrition. It would appear that for perchlorate there are still more questions than answers.
