Younger mothers’ breast milk has highest levels of flame retardants.
http://www.environmentalhealthnews.org/ehs/newscience/younger-womens-breast-milk-higher-levels-of-pbdes/

Daniels, JL, IJ Pan, R Jones, S Anderson, DG Patterson, LL Needham and A Sjödin. 2009. Individual characteristics associated with PBDE levels in U.S. human milk samples. Environmental Health Perspectives doi:10.1289/ehp.0900759.

Synopsis by Kim Harley, Ph.D.

Breast milk from young women – rather than from women older than 35 – has the highest measured levels of commonly used flame retardants known as PBDEs.

A study of breast milk samples from more than 300 women in North Carolina finds flame retardants contaminate the milk from almost three-quarters of the woman in the study. Women older than 35 had the lowest levels of PBDEs in their milk. The highest levels were measured in breast milk from women aged 25 to 29, followed by women younger than 25 years old.

The results suggest that younger mothers may have higher exposure to these flame retardant chemicals through their environment or lifestyles.

PBDEs are chemicals used in electronics, furniture, carpeting and textiles to reduce the risk of fire. In rats, early life exposures to PBDE has been associated with altered thyroid hormone function, hyperactivity and poorer learning and memory. Human health effects are not so well understood.

Most Americans have detectable levels of PBDEs in their blood. Dust and food may be the biggest sources for people. Breast fed babies are exposed through breast milk, however, experts agree that breastfeeding also provides important nutritional and immune benefits for the infant.

The study also found higher levels of these fat-soluble chemicals among obese women.

Interestingly, longer breastfeeding did not appear to lower PBDE levels in breast milk. Measured levels in breast feeding mothers a year after they gave birth were not significantly different from their levels when their infants were 3 months old. Having more previous pregnancies was also not associated with lower PBDE levels.

These findings are in contrast to other persistent pollutants, such as PCBs or DDT, which have been shown to decrease in the mother’s body and her breastmilk with longer breastfeeding. The author’s speculate that levels may not decrease either because mothers’ exposure to PBDEs is on-going or because maternal weight loss after pregnancy continues to mobilize PBDEs from fat stores.

The researchers measured and compared levels of individual and total PBDEs. Measured levels of total PBDEs in the samples were higher than those reported in other studies and ranged widely, from 1 to 2,010 nanograms per gram of fat.

PBDE compounds have been banned in Europe and several U.S. states, and legislation to further limit use in pending in many regions.