Testing in suburban California neighborhoods revealed methyl bromide in the air well beyond state mandated “buffer” zones at 12 out of 16 locations tested. The levels detected ranged from less than 1 part per billion to 294 parts per billion (ppb) on average over 12 to 24 hours. Single point measurements were as high as 1,900 ppb. The California Department of Pesticide Regulation (DPR) has estab- lished rules that allow individuals, including pregnant women and children, to be exposed to an average of 210 ppb of methyl bromide in the air over a 24 hour period as a result of agricultural application. Methyl bromide is known to cause birth defects (CCR 1994, OEHHA 1993) and is extremely toxic to the nervous sys- tem (CDPR 1995a, Pease 1996).
The California DPR standard for agricultural use of methyl bromide has been repeatedly criticized as too weak (Pease 1996, Wagner 1996). Indeed, some DPR scientists have recommended a much stronger 24 hour exposure standard as low as 1 ppb (CDPR 1995b). The one-day DPR standard of 210 ppb is well above the Minimum Risk Level recommended by the U.S. Public Health Service of 50 ppb exposure on average over 24 hours (ATSDR 1996). Methyl bromide levels in air exceeded the U.S. Public Health Service recommended 24 hour safety standard at three locations –– Ventura, Watsonville, and Castroville –– in tests conducted by independent technicians under contract to EWG. Those air samples were taken on residential property outside of buffer zones –– that is, in supposedly safe areas.
The 24 hour warning level for indoor methyl bromide exposure is even more stringent: 15.5 ppb, or thirteen and one half times more protective than the stan- dard for agricultural use (Sears 1997). The practical effect of this double standard is that Californians can be legally exposed to thirteen times more methyl bromide on their front porch than in their living room. This flagrant inconsistency breaches a fundamental tenet of toxicology: The dose (not the location) makes the poison.
Air monitoring by EWG has shown that Californians are exposed, perhaps rou- tinely, to levels of methyl bromide from agricultural applications that would be considered unsafe and require written safety warnings if the exposure resulted from indoor application of the compound. Three measured 24 hour average lev- els, plus four individual grab samples in a total of five different locations exceeded this 15.5 ppb standard.
