Sunday, October 12, 2014
Dubious support for a popular health scare
There is a substantial body of people who get their jollies out of finding "threats" to health in popular products. They obviously want to appear wiser than the rest of us poor sods. There seems to be no accepted name for them but I call them "food & heath freaks". They are probably best known for their unfounded demonization of salt, saturated fat and artificial sweeteners such as Aspartame. Sugar is their current big boogeyman.
A somewhat less well-known scare is about Bisphenol A, a component of many plastics. A few molecules of BPA have been shown to leach out of plastic bottles into the liquid contained in the bottle. For that reason plastic bably bottles have been more or less banned and glass baby bottles are mostly used instead. Glass is of course fragile and dangerous when broken but any decrease in safety from its use in baby bottles is ignored by food & health freaks.
The question is, however, how toxic is ingested BPA? Rats given enough of it certainly fall ill but as Paracelsus pointed out long ago, the toxicity is in the dose. And it seems unlikely that a few molecules received from a plastic bottle are harmful. And that is what most studies of the matter show. Like a terrier that won't let go of a bone, however, "research" to detect harm goes on among the food & heath freaks.
The latest stab at BPA has just come out in JAMA and I give the abstract below. I have however read the whole article and I would summarize the results rather differently. What they found was that the amount of BPA in the pregnant mother's blood correlated marginally significantly (p = .03) with the infant's lung function 4 years after birth but not 5 years after birth. That is a very shaky finding indeed and shows, if anything, that BPA is safe. They also looked at the correlation between mother-reported wheezing in the kid and BPA levels but that correlation failed to reach statistical significance (p = .11).
They do however rather desperately hang their hat on a correlation with wheeze drawn from the BPA concentration in the mother at 16 weeks. That correlation had vanished at 26 weeks gestation however so again the results actually show that BPA is safe -- no lasting ill-effects.
Not much there for the BPA freaks. I am not alone in that conclusion. The abstract follows:
Bisphenol A Exposure and the Development of Wheeze and Lung Function in Children Through Age 5 Years
Adam J. Spanier et al.
Bisphenol A (BPA), a prevalent endocrine-disrupting chemical, has been associated with wheezing in children, but few studies have examined its effect on lung function or wheeze in older children.
To test whether BPA exposure is associated with lung function, with wheeze, and with pattern of wheeze in children during their first 5 years.
Design, Setting, and Participants
A birth cohort study, enrolled during early pregnancy in the greater Cincinnati, Ohio, area among 398 mother-infant dyads.
We collected maternal urine samples during pregnancy (at 16 and 26 weeks) and child urine samples annually to assess gestational and child BPA exposure.
Main Outcomes and Measures
We assessed parent-reported wheeze every 6 months for 5 years and measured child forced expiratory volume in the first second of expiration (FEV1) at age 4 and 5 years. We evaluated associations of BPA exposure with respiratory outcomes, including FEV1, child wheeze, and wheeze phenotype.
Urinary BPA concentrations and FEV1 data were available for 208 children and urinary BPA concentrations and parent-reported wheeze data were available for 360 children. The mean maternal urinary BPA concentration ranged from 0.53 to 293.55 ‘g/g of creatinine. In multivariable analysis, every 10-fold increase in the mean maternal urinary BPA concentration was associated with a 14.2% (95% CI, -24.5% to -3.9%) decrease in the percentage predicted FEV1 at 4 years, but no association was found at 5 years. In multivariable analysis, every 10-fold increase in the mean maternal urinary BPA concentration was marginally associated with a 54.8% increase in the odds of wheezing (adjusted odds ratio, 1.55; 95% CI, 0.91-2.63). While the mean maternal urinary BPA concentration was not associated with wheeze phenotype, a 10-fold increase in the 16-week maternal urinary BPA concentration was associated with a 4.27-fold increase in the odds of persistent wheeze (adjusted odds ratio, 4.27; 95% CI, 1.37-13.30). Child urinary BPA concentrations were not associated with FEV1 or wheeze.
Conclusions and Relevance
These results provide evidence suggesting that prenatal but not postnatal exposure to BPA is associated with diminished lung function and the development of persistent wheeze in children.
Posted by John J. Ray (M.A.; Ph.D.).