Editors Note: Urgent News Important Corrections Regarding Milk Press Coverage

The recent “report” on perchlorate and milk contains serious mistakes that unfortunately have been repeated in subsequent press coverage.

Example 1: The report states that “The average perchlorate level in milk tested by the state, 5.8 ppb, is essentially the same as the maximum safe level of the just-adopted (California) public health goal.”

This is a fundamental mistake. You cannot equate a concentration of perchlorate (or any other chemical) in milk to the Public Health Goal (PHG), which is based on drinking 2 liters of water per day. People do not drink this much milk. Both must be converted to a dose. When you do, the dose of perchlorate a person would get is a fraction of the PHG.

Example 2: The report states, “…7 percent of women of childbearing age would get a daily dose of rocket fuel larger than the level currently considered safe by the EPA. But children are by far more at risk: Half of all children 1 to 5 would exceed EPA’s provisional daily safe dose just by drinking milk, and more than a third would get twice that dose. One-third of children 6 to 11 would get a larger dose than EPA says is safe, with one-fifth consuming twice as much.”

However, EPA acknowledges that much higher levels are ‘safe’: “The RfD is defined as an estimate, with uncertainty spanning perhaps an order of magnitude, of a daily exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of adverse effects over a lifetime.”


EPA also states: “This definition does not mean that exposure levels above the RfD are unsafe. Rather, the RfD value is in the center of a range of uncertainty that surrounds the best estimate of a ‘safe’ level. The scientific uncertainty spans from one-third of the RfD to three times the RfD. In the case of a range, the uncertainty spans from one-third of the lower bound to three times higher than the upper bound. In the case of perchlorate, where the reference range is 4-18 ppb, the uncertainty spans from 1.3 ppb to 54 ppb.”

EPA also acknowledges that the scientific community has not reached a consensus about the accuracy of their proposed RfD, and in fact numerous scientific individuals and groups have concluded that much, much higher levels of perchlorate exposure are perfectly safe. EPA states, “the draft RfD for perchlorate is still undergoing science review and deliberations both by the external scientific community and within the Agency.


California public health officials have already considered milk as a possible source of perchlorate exposure and there is no danger to anyone.

1. California’s Office of Environmental Health Hazard Assessment (OEHHA) already considered perchlorate in milk in developing the perchlorate Public Health Goal (PHG). OEHHA’s assumptions about the relative contribution of perchlorate as a source are appropriate, even based on the milk data presented in yesterday’s report:

“.scientific evidence suggests that the estimated exposure to perchlorate in water is greater than from other sources. For this reason, the RSC [relative source contribution] for this PHG is set at a level of 60 percent (instead of 20-50 percent) because OEHHA believes that the daily exposure to perchlorate would be predominantly from contaminated drinking water, not from other sources, e.g., food. .DHS has indicated that based on a review of current research data, there is no imminent health threat from perchlorate in food that would require a change in diet.” (Source: CA OEHHA 2004. PUBLIC HEALTH GOALS FOR CHEMICALS IN DRINKING WATER PERCHLORATE, page 2.)

2. The relative source contribution accounts for perchlorate in cow’s milk and this is found in the calculation of the California PHG

“The following equation was used to estimate health-protective water concentrations (C, in mg/L) for pregnant women:”

    C = BMDL × RSC × (BW/WC)UF

    = 0.0037 mg/kg-day × 0.6 × (25.2 kg-day/L)10

    = 0.0056 mg/L (rounded to 0.006 ppm, or 6 ppb)

    RSC = relative source contribution; a value of 60 percent is used for pregnant women to account for exposure to perchlorate in food such as farm produce and cow’s milk.” (Source: CA OEHHA 2004. PUBLIC HEALTH GOALS FOR CHEMICALS IN DRINKING WATER PERCHLORATE, page 84.)

Other problems with the milk report.

  • This work is not peer reviewed by scientists or medical experts.
  • Their work does not present the methods, materials, and raw data to check the assumptions and calculations; this is a fundamental violation of the scientific method.
  • This work is not released via the customary method of scientific work, by a peer-reviewed journal that assures adherence to appropriate scientific standards.

There are no health effects from minute traces of perchlorate in milk or water.

1. Perchlorate in milk acts the same way as perchlorate in drinking water and credible science has shown no evidence that low levels of perchlorate in drinking water are capable of having any effect on the health of adults, children or fetuses. A summary of these studies includes:

  • Tellez, et al. (2004). This study examined pregnant women and babies from three cities in Chile, where perchlorate levels range from non-detect to 110 parts per billion (ppb) in water. Preliminary analysis of the findings has found no impacts on the women or on fetal development.
  • Greer, et al. (2002). This study found no impact of perchlorate at levels below 180 – 220 ppb.
  • University of California, Irvine Urban Water Research Center report “Perchlorate and Drinking Water: A Science and Policy Review (2004).” While this report stopped short of saying what levels of perchlorate should be allowable in water, it did state “health benefits for reductions of exposure in concentrations in drinking water below 100 µg/L are difficult to demonstrate.” (100 µg/L is equal to 100 ppb)

2. The first measurable effects of perchlorate on the human body (which Greer shows don’t begin until about 200 ppb) are themselves harmless. The body reacts to these levels of perchlorate the same way it reacts to a serving of broccoli or Brussels sprouts, which produce the same effect on the body as perchlorate. According to the research, only at very high levels of perchlorate (at least 17,000 ppb) – consumed daily – could there be even a risk of any adverse effect.

3. The health effects of perchlorate are currently under review by a panel of the National Academy of Sciences, which is expected to issue its report later this year. California, like Massachusetts and the U.S. Environmental Protection Agency, has stated it will consider the findings of the panel before deciding whether to move forward in setting a standard for perchlorate in drinking water.