Misleading headlines on American exposure to BPA

Recent articles have been sounding the alarm with assertions that US citizens have two times more BPA in their urine than Canadians.  In an article that compared the national studies, the author cited a number of possible differences between Americans and Canadians that she believed could account for the difference.   One factor mentioned was thermal paper.  However, thermal paper is unlikely to play a role in the differences observed between Americans and Canadians.

Could thermal paper account for the difference?

First, there is no indication that the use of thermal paper is substantially different in the US and Canada.  BPA has been used in thermal paper since the 1960’s, though it came into more common use in the 1990s – so it is not a new phenomenon that has occurred exclusively in the US.

Second, health agencies in the US, Europe, Canada and the World Health Organization have determined that most of BPA exposure is from food sources; therefore BPA in thermal paper could not possibly result in doubling exposures.  In fact, absorption through the skin is thought to account for only 1 percent of total BPA exposure.

Additionally, studies have demonstrated that the small amount of BPA that is absorbed through the skin is rapidly metabolized, similar to its metabolism for oral doses.  So, dermal exposure poses no greater health concern nor results extended exposures.

What may account for the difference between Americans and Canadians

The Canadian Health Measures Survey (CHMS) and the US National Health and Nutrition Examination Survey (NHANES) have different methods for tracking and controlling for fasting, last urinary void, and the time of day of specimen collection.  Since exposure to BPA is almost exclusively from food and BPA is rapidly excreted in the urine, differences in the methodology to account for these factors is likely to skew the data and make the variation between US and Canada seem more extreme.

In addition, the timeframe of the studies was different.  US NHANES data was collected in 2003-2004.  The Canadian Health Measures Survey data was collected in 2007-2009.  The use of reusable polycarbonate water bottles declined over this period and could account for the lower levels of BPA in the later study.

What does this difference mean?

Even if you take the differences at face value, the difference is between 1.4 µg BPA/g creatinine (1.16µg/L urine) in Canadians to 2.6 µg/g creatinine (2.6µg/L urine) in Americans [a microgram (µg) is 0.000001g].  This different is incredibly small.

For comparison, the United States and Europe have adopted the standard that consumption of 50 µg/kg body weight/day is safe.  That’s 300ug/day for someone who weighs 132 pounds and regulators have built in margins of safety to this figure.

A good effort putting this data into perspective can be found at the Huffington Post.

New study confirms : No safety risk to workers from thermal paper

A new study by researchers at the Institut National de Recherche et de Se´curite´ in France (Marquet et al., Arch Toxicol2011) confirms that thermal paper receipts do not pose a safety risk to workers.

The paper supports the conclusion of previous research by Biedermann et al., which found that even “worst case” exposures to thermal paper receipts – exposures by cashiers to the material for 10 hours or more a day – are lower than international safety estimates (Total Dietary Intake, or TDI) for high exposures.

According to the new study, maximal exposure to BPA from one hour of exposure to the entire hands and forearms would be 4 µg/kg/day, or 12.5-fold lower than the daily safe exposure level (TDI) of 50 µg/kg/day.

Since exposure to thermal paper is unlikely to include so much surface area (hand and forearms)the conclusion indicates that normal handling of thermal paper is indeed quite safe for consumers and workers.

The paper further corrects a concern expressed in the Biedermannpaper that moisture or greasy conditions on the skin could increase the rate of BPA dermal penetration.  According to Marquet et al., their results indicated no significant differences in the presence or absence of occlusion, which would be expected to increase moisture on the skin.

For further information:

Marquet at al.:http://www.springerlink.com/content/t779340680t016t8/
Biederman et al.:http://www.springerlink.com/content/d5j507113141120h

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Thermal paper poses no health risk

There is no evidence that thermal paper containing BPA poses any health or safety risk to the public or to workers who handle it on a frequent basis, according to the most recent review of all relevant studies by the nonprofit Environmental Health Research Foundation.  Specifically, the Foundation “found no evidence to suggest adverse health effects from the small amounts of BPA that may migrate from thermal paper to human skin.”   It also found no evidence to support commercial advertising claims suggesting that the use of “BPA-free” thermal paper presents any health or safety benefit to cashiers or other workers handling such paper.   The fully documented report can be found here.

Evidence found lacking in chemosphere study

three ideas to help you create like a pro app development companiesA study recently published online by the journal

Chemosphere (Zalko et al, 2010) has attracted some media attention for its claims that BPA from thermal paper is efficiently absorbed through the skin, where it is converted to water-soluble metabolites (byproducts of BPA, once it is metabolized in the human body).  These byproducts are known to be completely lacking in estrogenic activity and are efficiently excreted from the body in urine.

The authors claim the inactive BPA metabolites are then re-converted into an estrogen-active substance, and that this process “contributes substantially” to BPA exposure due to breakdown of the metabolite and release of free BPA within the body.

This is a very troubling conclusion, as the authors provide no evidence that inactive BPA metabolites are reconverted into estrogenic BPA in the human body.  Therefore, this appears to be simply speculation on the part of the study’s authors.