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Appendix: Study Details

September 4, 2008

Fire Retardants in Toddlers and Their Mothers: Appendix: Study Details

About Participants

Paired blood samples were collected on the same day from 20 mothers and their first born children. Our child participants were 1.5 to 4 years old (average age 3 years). All were were living in the same house as their mother during the study. 8 of 20 mothers were multiparous, and 3 more were pregnant at the time of blood testing. The majority of our study participants are Caucasian. 1 participant is African-American and another is Latina. Their ages range from 28 to 44 years old. All are college graduates. All children were breastfed as infants for at least 4 months, with 14 of 20 for longer than 1 year. This is a longer duration of breastfeeding than is typical for American children. The study participants reside in 16 cities in 11 U.S. states: Alaska, California (5), Colorado, Connecticut, the District of Columbia (3), Massachusetts, Minnesota, Montana (3), New Mexico, Oregon, and Washington (2). We collected substantial information from participants about their diet, household products, occupation and places of residence. We found no obvious relationship between PBDE concentrations and mother or child's age, mother's occupation, duration of nursing, participant's body mass, diet or other household factors. None of our participants reported unusual contact with foam furnishings or electronics in their home, daycare or workplace.

Study process

All adult participants gave informed consent prior to study enrollment with both custodial parents giving consent for children's participation. The study received Institutional Review Board approval (Independent Review Consulting, Inc., Corte Madera, CA, USA). The blood sampling was performed between September 2006 and January 2007, at 16 commercial laboratories. Laboratory technicians centrifuged the samples and pipetted the serum into vials, using chemically clean glassware provided by EWG. Phlebotomists were instructed to fill a 10 ml vaccutainer as completely as possible from the child, and then collect 2 similar-size samples from the mother. This sampling design sought to both maximize serum available from young children, and to minimize any chance that larger sample volume for mothers would result in systematic differences between mother and child measurements. Two equal volume samples were collected from mothers and both samples were analyzed for QA/QC purposes. The samples contained an average of 3.5 grams of serum for children and 3.4 grams for adults. The chemical analyses were performed by Dr. Åke Bergman and colleagues at Stockholm University's Department of Environmental Chemistry. This is a highly regarded laboratory with decades of publications on PBDE and PCB levels in biological and environmental samples. The laboratory used GC/MS, using authentic reference substances. Samples were analyzed for 20 PBDE congeners and 11 were detected, each in at least 25% of participants. Congeners detected include: PBDE-28, -47, -85, -99, -100, -138, -153, -154/BB-153, -183, -197, -209. The following congeners were not detected: PBDE-17, -66, -71, -196, -201, -203, -206, -207, -208. We collected 40 primary samples (20 maternal, 20 children), as well as double samples from 17 of 20 mothers. There was high concordance between measurements for the 2 maternal serum samples as well as the 10 split samples performed by Stockholm University. All results were background adjusted and reported as concentrations in lipid. When duplicate samples were analyzed we averaged the 2 reported values.