Researchers at UC San Francisco performed a meta analysis which found a clear connection between a flame retardant commonly found in furniture and household products and lower IQ in children. The study was published in Environmental Health Perspectives August 3, 2017.
Read more here.
Developmental PBDE Exposure and IQ/ADHD in Childhood: A Systematic Review and Meta-analysis
https://doi.org/10.1289/EHP1632