Bisphenol A (BPA) is a chemical widely used in the production of plastics and resins, found in everyday items such as water bottles and food packaging.
Despite its prevalence, the safety of BPA and its potential effects on human health are subjects of ongoing debate among scientists and regulatory bodies.
In this article, we’ll explore the study behind the 93% statistic, while delving into the nuances of this debate surrounding BPA.
The study behind the 93% statistic
The study behind the 93% is titled Exposure of the U.S. Population to Bisphenol A and 4-tertiary-Octylphenol: 2003-2004 and measured BPA concentration in urine.
The data used to conduct the study was gathered from the 2003 - 2004 National Health and Nutrition Examination Survey — a survey conducted by the Centers for Disease Control and Prevention’s National Center for Health Statistics that’s designed to measure the health and nutritional status of the civilian noninstitutionalized population in the US.
Survey participants:
- Participated in household interviews
- Provided their medical history
- Took part in standardized physical examinations
- Allowed for the collection of biologic specimens (i.e. blood / urine) “for clinical chemistry testing, nutritional indicators assessments, and assessment of exposure to environmental chemicals.”
The study methodology
Participants of the NHANES survey are selected by their age, sex, and racial/ethnic background using a statistical analysis process that utilizes the most recent US Census data that’s available.
One-third, or a 2517 person subset, of the people that participated in the NHANES survey were used in this study on BPA and tOP.
Their urine samples were analyzed for BPA concentration “using automated solid-phase extraction coupled to isotope dilution–high-performance liquid chromatography–tandem mass spectrometry.”
Urine samples were only collected on persons 6 years of age or older, so this study did not measure BPA levels in urine for people under 6 years of age.
Who conducted the study?
The study was conducted by Antonia M. Calafat, Xiaoyun Ye, Lee-Yang Wong, John A. Reidy, and Larry L. Needham.
The authors declared they “have no competing financial interests.”
Is it accurate?
The study found that 92.6% of persons in the sample group had detectable levels of BPA in their urine.
But the bigger takeaway was that this study also found statistically significant variances in BPA levels in urine by race/ethnicity, age, sex, and household income.
The charts below show these variances.
The measurement being utilized is the least square geometric mean (LSGM), a measure of central tendency that is less sensitive to extreme values compared to an arithmetic mean.
BPA concentration in urine by race/ethnicity
The study found that least square geometric mean (LSGM) concentrations of BPA in Mexican Americans were significantly lower than in both non-hispanic black and non-Hispanic white populations:
BPA concentration in urine by sex
The study found that LSGM concentrations of BPA in females were statistically higher than in males:
BPA concentration in urine by age
The study found:
- Children had higher LSGM concentrations of BPA than adolescents.
- Children had higher LSGM concentrations of BPA than adults.
- Adolescents had higher LSGM concentrations of BPA than adults.
BPA concentration in urine by income
The study found that LSGM concentrations of BPA in the high household income category were lowest:
The study is 2 decades old. What about now?
In 2008 and 2009, this study made headlines.
You’d expect these headlines to increase consumer awareness of BPA in the products being used and consumed, leading to a decrease in BPA urine concentration.
So, has BPA concentration in urine been on the decline?
Turns out, yes.
Bisphenol A in women ages 16 to 49 years: Median and 95th percentile concentrations in urine, 2003-2016 (Indicator B11)
Median BPA in women ages 16 to 49 has decreased from 3.1 micrograms per liter in the 2003-2004 survey to 1 microgram per liter in the 2015 to 2016 survey.
The 95th percentile in women ages 16 to 49 has decreased from 15.9 micrograms per liter in the 2003-2004 survey to 6.4 microgram per liter in the 2015 to 2016 survey.
Bisphenol A in children ages 6 to 17 years: Median and 95th percentile concentrations in urine, 2003-2016 (Indicator B12)
Median BPA in children ages 6 to 17 has decreased from 4 micrograms per liter in the 2003-2004 survey to 1.2 microgram per liter in the 2015 to 2016 survey.
The 95th percentile in children ages 6 to 17 has decreased from 16 micrograms per liter in the 2003-2004 survey to 7.1 microgram per liter in the 2015 to 2016 survey.
The real question: Is BPA toxic to humans?
We now know that according to this study, BPA exists in the urine of 92.6% of people, and that BPA concentrations in urine appear to be on the decline.
But this begs the questions — is BPA toxic to the human body? If it is, at what levels?
It turns out, it’s highly debated — on one side you’ve got FDA scientists who state there’s no danger in BPA, and on the other you’ve got academics who are certain there is.
The FDA’s CLARITY-BPA analysis
In 2018, the FDA released their findings from a multi-year, multi-million dollar analysis they had conducted on BPA as part of the CLARITY-BPA program.
The big question of the study — is BPA safe for humans and at what levels?
Here’s the FDA’s statement in response to that question:
“Yes. Based on FDA's ongoing safety review of scientific evidence, the available information continues to support the safety of BPA for the currently approved uses in food containers and packaging. People are exposed to low levels of BPA because, like many packaging components, very small amounts of BPA may migrate from the food packaging into foods or beverages. Studies pursued by FDA's National Center for Toxicological Research (NCTR) have shown no effects of BPA from low-dose exposure.” - www.fda.gov
Critiques of CLARITY
In an investigation conducted by Environmental Health News, a number of critiques were uncovered about CLARITY, mainly from other scientists.
Here’s a summary of those critiques:
1. Study design
Critiques surrounding study design include:
- BPA is considered by many scientists to be a hormone disruptor. However, a type of rat was used for the study that had been shown to not be sensitive to hormone disruptors, potentially dampening effects from BPA in the study.
- The administration of BPA to rats in the study used an invasive process called gavage, where a tube is inserted down the animal’s throat to administer the BPA in the rat’s stomach. Due to gavage being an obviously stressful procedure, there are critiques that this method of administration altered hormone levels.
2. Contamination
If 93% of humans have BPA in their system, we know the contamination is widespread.
There’s a possibility that if the rats in the main study were accidentally exposed to BPA before the study began (through their plastic cage, etc.), it would have reduced the difference between the test and control groups.
3. Statistical assumption
In statistics, there are the concepts of a false positive and a false negative.
A false negative is when something harmful is said to be safe. A false positive is when something safe is said to be harmful.
The FDA is said to prefer to avoid false positives, meaning they are very careful not to wrongly say something is harmful, which means they’re more susceptible to false negatives (i.e. saying something is safe when it’s not).
4. Downplaying health effects
There were health effects that did emerge from the data like mammary gland cancer in the rats, but these effects were said to be downplayed by the FDA.
The FDA essentially threw this data out because mammary gland cancer wasn’t observed at the highest doses.
5. Industry influence
There are critiques of industry influence on the FDA, like a reliance on industry-funded studies, or the very real potential that if the FDA did ban BPA without evidence that would hold up in court, they’d likely get sued by the BPA industry.
6. Outdated testing methods
There are critiques that the FDA used outdated methods to test BPA in the CLARITY study.
The techniques that were used were decades old and don’t always detect the subtle ways that chemicals like BPA interact with the human body.
7. Superiority complex
There are critiques that the FDA displays a superiority complex, implying their scientists are better than others, including those whose work is published in peer-reviewed journals.
This poses potential problems when it comes to changing their mind as new evidence surfaces.
8. The dose makes the poison
At the heart of the disagreement is an old principle — “the dose makes the poison.” This means that the danger of a chemical depends on its amount: more of it means more harm.
The FDA uses this idea to judge if chemicals in food are safe, expecting a clear pattern where more of the chemical always equals more toxicity.
However, they often test only at high doses and then guess a safe level from those results. In contrast, experts on hormones find that small and large doses of chemicals can have unexpected effects, like low doses causing more harm than higher ones.
Scientists have discovered that very small amounts of hormone-like chemicals can activate bodily responses, but increasing the dose might stop this effect, suggesting nature's way of preventing an excessive response to hormones.
Potential flawed measurement underestimates BPA exposure
On December 5th, 2019, a study published in The Lancet Diabetes and Endocrinology that utilized a new BPA testing method developed by researchers at Washington State University hinted at the possibility that measurement of BPA in urine might be wildly inaccurate.
Prior studies showed BPA in urine to be at around 1.2 nanograms per milliliter, but in this study, they found it to be 51.99 nanograms per milliliter — an astonishing 44 times larger.
Final Thoughts
The study "Exposure of the U.S. Population to Bisphenol A and 4-tertiary-Octylphenol: 2003-2004" highlights that 92.6% of Americans have detectable BPA levels in their urine, with significant demographic variations.
Over the years, BPA concentrations have generally decreased, but what level is toxic to humans is still widely debated.
The FDA maintains BPA's safety for currently approved uses despite criticisms on how they’re interpreting the data being used to support this stance.
Further complicating matters, new testing methods suggest BPA exposure may be significantly underreported, challenging existing safety assessments and regulatory stances.
Given the ongoing debate over BPA's safety, it's prudent for consumers to be aware of the risks and choose to err on the side of caution in light of scientific uncertainty.
