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US Government study casts significant doubts over bisphenol A threat

By Rory Harrington , 14-Sep-2011
Last updated on 14-Sep-2011 at 16:23 GMT2011-09-14T16:23:33Z

Humans are so efficient at ridding the body of bisphenol A (BPA) that bioactive levels of the chemical left in the blood for absorption are undetectable, according to research from a host of US Government agencies.

The study, funded by the US Environmental Protection Agency (EPA), found that the blood serum of 86 per cent of subjects who were exposed to elevated dietary levels of BPA by eating canned foods over a 24 hour period contained undetectable amounts of the chemical.

The project– 24-Hour Human Urine and Serum Profiles of Bisphenol A During High Dietary Exposure by Justin Teeguarden et al – was carried out by scientists from the Pacific Northwest National laboratory, The US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) – which double-checked and verified the initial findings.

The team also questioned findings from other studies where high levels of the chemical had been detected in urine or blood.

“The evidence presented here and elsewhere for low-level contamination, even in the face of extraordinary attention to this problem, suggest that these infrequent positive determinations near the detection limit should be suspect,” concluded the scientists in the study published in Toxicological Sciences.

Several orders of magnitude less

In the clinical exposure study, 20 adult volunteers ate canned food only at three meals. Blood and urine samples were taken hourly over a 24-hour period to monitor levels of BPA.

The volunteers’ consumption of BPA- calculated from the average urinary excretion - was said to be 21 per cent higher than that of 95 per cent of the US population.

BPA in blood serum is significant as this represents the amount of the chemical that is free to be absorbed into body tissues. Levels in urine represent amounts that the body has processed and will excrete.

Maximum levels for the 86 per cent of blood samples were estimated to be 0.01nM, with the highest level recorded in the total of 320 samples taken reaching 5.7nM.

The study concluded that even the highest levels of BPA detectected in blood were one to three orders of magnitude lower than those believed to cause adverse health effects – even on “sensitive experimental” rats, the animals most used in studies on BPA exposure.

Raises serious questions

The North American Metal Packaging Association said: “The findings raise serious questions of the human relevance of many, if not all, studies that have purported to show adverse effects from BPA and/or studies that utilize methods of exposure that bypass the normal metabolic pathway from oral exposure in humans.”

“In a nutshell we can now say for the adult human population exposed to even very high dietary levels, blood concentrations of the bioactive form of BPA throughout the day are below our ability to detect them, and orders of magnitude lower than those causing effects in rodent exposed to BPA,”, lead author Teeguarden told Forbes.

BPA is a monomer used in the manufacture of polycarbonate plastics and the epoxy linings of food and drink cans. Its continued use in food packaging has triggered a heated debate with many citing studies that link human exposure to cancer, birth defects and many other illnesses. However, all major food safety authorities across the globe have said it poses no risk at current exposure levels.

Twenty-Four Hour Human Urine and Serum Profiles of Bisphenol A during High-Dietary Exposure - By Teeguarden JG, Calafat AM, Ye X, Doerge DR, Churchwell MI, Gunawan R, Graham MK

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