Breast Milk and PFASs - Part 3

The Mogenson paper "Breastfeeding as an Exposure Pathway for Perfluorinated Alkylates" that initiated the "Breast milk may be tainted with toxic chemicals" news articles on Google make this statement as to why PFASs are a possible concern if they are found in breast milk:

Adverse effects of PFASs reported in children with similar serum-PFAS concentrations include immunotoxicity, as revealed by decreased antibody concentrations toward childhood vaccines and increased frequency of common infections.

Let's look at their statement that PFASs result in an "increased frequency of common infections."

This is based on a single paper they cited titled:

Pre-natal exposure to perfluoroalkyl substances may be associated with altered vaccine antibody levels and immune-related health outcomes in early childhood.

 Here is what the author's of that cited paper conclude:

In the present study, PFAS concentrations were associated with reduced antibody levels to the rubella vaccine and increased number of episodes of common cold and gastroenteritis, suggesting that pre-natal exposure to various PFAS may lead to immunosuppression in early childhood.

Now I am not at all good with them there statistics these science papers use. I am, however, good enough to look stuff up and get a feel for what is going on with the data they report.  They say there are lies, damn lies, and statistics, and I agree.  I have read enough journal peer-reviewed papers to come away scratching my head as to how they can conclude what they do and put it in a paper for all the world to read.

The reason I am once again going on and on about a single topic is to provide support for why I think it has committed a wrong.  In this case, it is not that the data is wrong - it may or may not be - it is the simple fact that what they elude to - that "breastfeeding being an important exposure pathway to some PFASs in infants" sends the wrong message to the public and specifically mothers who want to do what is best for their baby.

Assuming that breast milk does increase the amount of PFASs in the baby, does that increase contribute to a negative health outcome?  The two papers they cite state that these compounds "may undermine childhood immunization programs" as well as "increased frequency of common infections."

Let's look at the evidence to support the "increased frequency of common infections."

According to the cited paper "Pre-natal exposure to perfluoroalkyl substances may be associated with..." the mothers in the study were asked in a questionnaire:

Concerning infectious diseases, the mothers were asked how many episodes of the following diseases/complaints the child had experienced in the last 12 months: common colds and other upper respiratory tract infections (hereafter called common cold), otitis media, pneumonia, gastroenteritis with vomit or diarrhea, and urinary tract infection.

The authors report:

When analyzing common cold for the third year of life as a binary variable (yes/no), no statistically significant associations were found (Table 5).

This means that there was no difference between the exposed group and the non-exposed group (the control) when asked the yes/no question on colds.

They then state:

With regard to infectious diseases, the maternal concentrations of PFOA and PFNA were positively-associated with the number of episodes of common cold for both the children’s third year of life and all 3 years merged. PFHxS was positively-associated with the children’s number of episodes of common cold for all 3 years merged in the bivariate analysis only (Table 5).

No statistically significant associations between perfluoroalkyl substances and the common cold,  otitis media, pneumonia, gastroenteritis with vomit or diarrhea, and urinary tract infection.

They state that they found that "increased concentrations of PFOA and PFNA were associated with increased number of episodes of common cold."

The statistical data they present in Table 5 resulted from:

Poisson regression analyses were used for health outcomes consisting of count data (number of episodes of common cold and and gastroenteritis),

Like I said earlier, I am not well versed in all things statistics.  So I went looking to see what the "β-value" in Table 5 means:

I went a Googeln' and found this helpful information:

Assuming I am understanding this correctly a higher  β-value supports the claim that "increased concentrations of PFOA and PFNA were associated with increased number of episodes of common cold."

With regard to infectious diseases, the maternal concentrations of PFOA and PFNA were positively-associated with the number of episodes of common cold for both the children’s third year of life and all 3 years merged. PFHxS was positively-associated with the children’s number of episodes of common cold for all 3 years merged in the bivariate analysis only (Table 5).

The question I have, when looking at Table 5's data for he common cold, is what does positively-associated actually represent here?

What the authors of this paper report is an increase that is statistically significant when the β-value had a p-value ≤ 0.05.

The data that gave them this statistically significance β-value in Table 5 that supports their claim of "positively-associated with the children’s number of episodes of common cold" comes from a questionnaire given to the mother.

At the age of 1, 2, and 3 years, a questionnaire was sent to the participants. ...Concerning infectious diseases, the mothers were asked how many episodes of the [common cold] the child had experienced in the last 12 months.

Yeah, these mom's may recall with 100% accuracy the number of colds their child got last year, and when you put all the numbers into the statistics computer program it spits out a β-value and a p-value, but does a p-value below 0.05 support anything other than the β-value being statistically significant?

Yippie!  I saved one dollar on my purchase of a new car!  That's a positive increase in my bank account!

If you look at the β-values associated with those p-values, they are not big numbers.  If you look at all the data on incidence of common colds reported by the moms, 50% showed no statistical significance.

The authors are not incorrect when they state "positively-associated with the children’s number of episodes of common cold" its just that the "positive" they are speaking about looks to be an insignificant increase.

When you add this to the fact that a questionnaire that asks a mom to recall the number of colds in the past year is fraught with bias and error, and you look at the very small number of participants, the support for the statement in the Mogensen paper on Breastfeeding that "adverse effects of PFASs reported in children with similar serum-PFAS concentrations include...increased frequency of common infections" should never have been made.

Do I need to show you the results for gastroenteritis or will you take my word for it that it paints the same picture as the common cold data in Table 5 did?

Statistically significant results should actually mean something other than they were statistically significant.

Next post: Part 4