Breast Milk and PFASs - Part 5

Let's look at the author's statement in their paper "Breastfeeding as an Exposure Pathway for Perfluorinated Alkylates":

a major concern [because] PFAS exposure may undermine childhood immunization programs.

Is it?  They cite two papers that make this claim:

1. Pre-natal exposure to perfluoroalkyl substances may be associated with altered vaccine antibody levels and immune-related health outcomes in early childhood
2. Serum Vaccine Antibody Concentrations in Children Exposed to Perfluorinated Compounds

Let's look at the first one.

Most clearly, a 2-fold increase in PFOS exposure was associated with a difference in [antidiphtheria] antibody concentration of -39% (95% CI, -55% to -17%) at age 5 years before the booster.

Thus, a 2-fold increase in PFOA exposure was associated with differences of -36% (95% CI, -52% to -14%) and -25% (95% CI, -43% to -2%) for tetanus and diphtheria, respectively.  

Okay...assuming that to be true, now we are looking at something that may be significant, not just statistically significant.

Why would this drop in antibody concentration be of a concern?

PFC exposures at commonly prevalent serum concentrations are associated with lower antibody responses to childhood immunizations and an increased risk of antibody concentrations below the level needed to provide long-term protection.

Okay...again, assuming their data does actually show a decrease, this is a concern.

What did the second paper show?

Based on the β -values, the strength of the association between rubella antibody-levels and PFAS concentrations were PFNA >PFOA >PFHxS >PFOS. No significant associations were found between the concentrations of PFAS and vaccine antibody levels to the other vaccines.

Though not in complete agreement, there is a case to be made that PFAS concentrations in serum blood impact antibody levels.

The first paper supports its findings stating:

Our findings are supported by several. though not all, experimental studies in rodents, in which adverse effects of PFOS on humoral immune function were observed at serum concentrations similar to those reported in the present study and at levels prevalent in the United States.

Why this lowered antibody levels might be considered a "major concern" is based on this:

An antibody concentration greater than 0.1 IU/mL is considered an important indicator of protection in accordance with the public health rationale for routine vaccinations. Prenatal and postnatal PFOS exposures, as well as postnatal PFOA exposure, were associated with increased odds of antibody concentrations below the protective level.

 Let's look at the data for the 1st paper cited.

Most clearly, a 2-fold increase in PFOS exposure was associated with a difference in [antidiphtheria] antibody concentration of -39% (95% CI, -55% to -17%) at age 5 years before the booster.

That's a result based on a model they generated:

Structural equation models were generated to determine the joint associations of PFCs with the overall antibody concentrations.

And those models were designed from the statistical data they calculated:

Multiple regression analyses with covariate adjustment showed that prenatal exposures to both PFOS and PFOA, as indicated by the maternal serum concentrations, were negatively associated with antidiphtheria antibody concentrations (TABLE 3)

 Let's look at Table 3:

See those 95% Confidence Intervals (CIa)? Here is what they show:

Confidence intervals provide an ‘estimate interval’, that is, a range of values around the point estimate within which the true value can be expected to fall.

In statistics, this statement is true:

The wider the confidence interval is, the more variability in the sample, and the less precise the point estimate.

The authors in the cited paper claim that "both PFOS and PFOA, as indicated by the maternal serum concentrations, were negatively associated with antidiphtheria antibody concentrations."

The CIs for these percent difference result range from a negative percentage to a positive percentage.

This means that although they report a negative number (a decrease in the percentage of antibodies when compared to a population that was not exposed), the true value falls between that range.  It could be any number between -31.9 and +18.7.

This range - from negative to positive - is seen in the majority of results in Table 3.  It appears that the authors ignored that. and focused on the mean value - a negative number - that the statistics program spat out.

This range, at least to me, makes the statement of a negative difference in antibody concentrations found, questionable.  Its too variable to say the mean is representative of the population at large.

Let's ignore that.  Let's assume that their negative numbers shown in Table 3 actually show that exposure results in a decrease of antibody concentration.  Let's forget about the values the model calculated with a 2-fold exposure, and just look at what they found.

Next Post" Part 6

Note: This was written earlier than post date.  My next post will explain why.