UK press coverage of claims that ingested traces of plasticizing chemicals of a sort commonly found in shower curtains, vinyl flooring, toys and some cosmetics could feminize little boys' brains prenatally, earned a prompt riposte from the National Health Service website, this week.

"Parents should not be concerned about 'gender-bending' phthalates,” the UK Health Service responded, pointing to acknowledged limitations in a University of Rochester study reported online in the International Journal of Andrology at the weekend.

“Although the BBC, Daily Telegraph and Daily Mail have accurately reported the sample size and main findings of the study, none of them mentions the most important limitation: that extremely few of the initial sample participated in the follow-up research sessions. When considered in isolation, the evidence gathered from this small number is unlikely to be representative of the whole sample.”

The NHS Choices commentary used the exchange between research and the media as the basis for an unusually thorough explanation of the strengths and weaknesses of numerically small cohort studies.

Since 1998, Shanna Swan has been leading the federally funded, multi-center Study for Future Families, which is collecting data to help scientists investigate environmental toxins.

They concluded their paper with a cautious public health warning about the accumulating evidence against phthalates and a call for more extensive research.

“Our results need to be confirmed, but are intriguing on several fronts," she announced. "Not only are they consistent with our prior findings that link phthalates to altered male genital development, but they also are compatible with current knowledge about how hormones mold sex differences in the brain, and thus behavior. We have more work to do, but the implications are potentially profound."

“Only 74 boys and 71 girls were assessed, which represents 45% of those who were invited to participate,” the NHS said in its rejoinder to the resulting UK news coverage, which focused on the attempts to identify the sexual influence of prenatal phthalate exposure in play behavior. “Numerous possible confounding factors were not taken into account.”

“The study design had strengths in that it used a validated scale for assessing child gender-type behavior and also took into account how parental attitudes may have influenced this.

“However, little is known about the effects of phthalates in humans, and as children’s play behavior is likely to be complex and affected by many factors, there are probably numerous other confounding factors that were not accounted for. Also, measuring phthalates in the urine at a single point during pregnancy is not a reliable indication of exposure levels over time." 

Choices wound up its argument with a string of bullet-points to support the argument that the evidence was too weak to form any definite conclusions”.

Coverage in the US medical press was less scornful. Medical News Today reported that the concern about phthalates was well founded and the work of Swan and her medical school colleagues in Iowa, Minnesota, Missouri and Cambridge UK entirely reputable

It reminded its readers that a federal law passed last year banned six phthalates from being used to make items such as teethers, soft books, bath toys, dolls and plastic figures.

Swan and her team had previously shown that phthalate exposure during pregnancy might affect the development of genitals of both male rodents and baby boys, and they called this cluster of genital alterations the "phthalate syndrome".

But the line between alert and alarm is a hard one to toe. What the NHS was presumably seeking to head off was anything on the lines of Children's Health Magazine’s analysis of acronym-infested, domestic chemical dangers represented in its story Your Big Fat House

That declared “Obesity-causing chemicals have invaded our homes. It's up to you to kick them out” and then rampaged from room to room.

“Bedroom – carpet (PBDEs), vinyl flooring (PVC), mattress (PBDEs), toys, (BPA), waterproof clothing (Phthalates, PFOA)
One study found that children who live in homes with vinyl flooring in the bedrooms are twice as likely to have autism. To further avoid EDCs in your bedroom: 1) Make sure the mattresses and mattress covers you buy aren't treated with brominated flame retardants. 2) Avoid clothing that's been coated with a water-, stain-, or dirt-repellent. 3) Throw out plastic toys that aren't designated "BPA free" (old plastic leaches more toxins).

“Foyer – raincoats (phthalates), rain boots (phthalates), faux leather coats, shoes, purses, and briefcases (phthalates)
PVC might be an obvious component of rain slickers and Wellies, but the phthalate-laden material is almost always found in soft fake-leather accessories as well. To avoid exposure: 1) Buy real leather accessories. 2) Try waxed canvas rain gear instead.

“Laundry room – PVC pipes, detergents, and dryer sheets (phthalates)
Most cleaning products contain phthalates, and their containers have BPA. But SC Johnson, the maker of Windex, Shout, Pledge, and Scrubbing Bubbles cleaning products, has started to list ingredients on its products…" Enough!

See: Swan S H, Liu F, Hines M, Kruse R L, Wang C, Redmon J B, Sparks A and Weiss B, “Prenatal phthalate exposure and reduced masculine play in boys” pre-published online by the International Journal of Andrology.