Cherry-Picked Science Leads To Irresponsible Conclusions

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On Feb. 20, a large headline from CNN crosses my screen: ‘’Chemicals in plastics damage babies’ brains and must be banned immediately, expert group says”. A shocking, scary headline based on cherry-picked data that misleads the public. What are these chemicals that must be banned immediately?

It is phthalates, a group of chemicals that are used to soften plastic. These chemicals are one of the most studied groups of chemicals in use today. Since they are very stable and bound tightly into vinyl’s structure, they do not readily migrate out of the product.

Phthalates are present in consumer products, medical devices, including IV storage bags, wire, cable, and outdoor products, such as garden hoses.  The FDA already has carried out risk assessments on the release of phthalates from medical devices and has provided guidance to industry on the acceptable levels of phthalates in these products. The EPA is currently carrying out multi-year risk assessments on several phthalates under the Toxic Substances Control Act (TSCA). 

Scientific Conclusions

These chemicals have been extensively reviewed by governmental and scientific agencies worldwide, with the following conclusions: 

  • No public health concern with the current uses of diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) in gloves, footwear, children’s school materials, shower curtains, and other everyday uses. The presence of these phthalates in food or dust did not present a health concern. European Chemicals Agency (2013)
  • No public health concern with DINP or DIDP, and they do not constitute a danger in Canada to human life or health. Environment and Climate Change Canada (2017)
  • DIDP can be used in sensitive applications like toys and childcare products without any restrictions, as it poses no harm to children or pregnant women at current exposure levels. U.S. Consumer Product Safety Commission (2017)
  • DINP does not show adverse effects on sexual function, fertility, or fetus development. European Chemicals Agency (2018)

CNN’s Conclusions

The CNN article is based on a paper reported in the American Journal of Public Health that should serve as a “wake-up call to understand that early-life exposure to this class of chemicals is affecting our children.”

What is in this paper to lead to such a wake-up call?

This paper summarizes epidemiological evidence on adverse neurodevelopmental effects following prenatal exposure to phthalates. The study concludes that all phthalates (there are hundreds of individual chemical compounds in this group) should be banned from all products based on the available scientific evidence. They conclude that no phthalate compound should be allowed to be substituted for another phthalate compound.

However, this paper does not use systematic review methodology but, instead, “cherry-pick” those reports most favorable to its conclusions. It uses a variety of techniques, including:

  • Introducing results that agree with your conclusions from a few papers, using “For example…” to begin the sentence.
  • Note studies that disagree with those prior studies but dismiss them in a paragraph starting with, “It is important to note that the literature is not entirely consistent.”  
  • Ignore recent articles or systematic reviews that come to conclusions that contradict your own. More specifically, a recent systematic review by EPA researchers that concluded

“Overall, this detailed systematic review suggests that there is limited evidence that phthalates adversely affect the examined neurodevelopmental domains.”

As a scientist, I believe that we need to redouble our efforts not to mislead the public. That is why comprehensive systematic reviews of environmental health issues rather than agenda-driven cherry-pick “reviews” are necessary. And it is also why balanced, scientifically literate reporting, not intended to garner attention through fear, is so important.