As millions of acres of farmland in the U.S. Midwest and South recover from Mississippi River flooding, scientists report that river flooding can increase levels of potentially harmful flame retardants in farm soils. But the higher levels apparently do not find their way into the milk produced by cows that graze on these lands, according to a study in the ACS journal Environmental Science & Technology.
Iain Lake and colleagues note that the flame retardants, called PBDEs, are found in a variety of household products including furniture upholstery, textiles, cars, plastics, and electrical equipment. PBDEs "are increasingly being associated with endocrine disruption, neurotoxicity, reproductive and developmental toxicity, and potential cancer in animals studies," they write. Fatty foods such as milk and meat accumulate PBDEs, making those foods a potentially significant source of PBDEs consumed by humans.
Working along the River Trent in the United Kingdom, the researchers examined whether PBDE levels in the soils, grass, and milk obtained from grazing cows would differ between flood-prone and non-flooded farms along the river. While flood-prone fields contained significantly higher levels of PBDE from river sediments, this increase did not translate into higher PBDE levels in the grass growing in the soils. Moreover, "this study provides no clear evidence that the grazing of dairy cattle on flood-prone pastures on an urban and industrial river system leads to elevated PBDE levels in milk," Lake and colleagues write.