You probably won't read about this in mainstream media outlets such as The New York Times, the Washington Post or The Los Angeles Times, but lookey here: on October 31, 2005 the prestigious National Academy of Sciences published on line a study concluding:
Perchlorate is a goitrogenic anion that competitively inhibits the sodium iodide transporter and has been detected in forages and in commercial milk throughout the U.S. The fate of perchlorate and its effect on animal health were studied in lactating cows, ruminally infused with perchlorate for 5 weeks. Milk perchlorate levels were highly correlated with perchlorate intake, but milk iodine was unaffected, and there were no demonstrable health effects. We provide evidence that up to 80% of dietary perchlorate was metabolized, most likely in the rumen, which would provide cattle with a degree of refractoriness to perchlorate. Data presented are important for assessing the environmental impact on perchlorate concentrations in milk and potential for relevance to human health.
A 60-kg pregnant woman could consume in excess of 3.7 liters of milk containing 11.3 ng of perchlorate per ml without exceeding the RfD, and this quantity of milk would be well in excess of average daily consumption.
Don't hold your breath waiting to hear our legislators and regulators cite this study as at least some evidence that caution is needed in allocating scarce resources to perhaps more pressing problems. In environmental politics, the keyword remains politics.