What are the results of the MDHHS’ Michigan Long-Term PBB study?
The Michigan Long-Term PBB Study has been very valuable to understanding the effects of PBBs on health. Researchers have been fortunate to have the partnership of the community affected by this chemical mix-up as work continues in the effort to assess the health effects that they and their children have experienced in the 30 years since their initial exposure. Much of what scientists know about the health effects related to PBB exposure in people has been learned from this Michigan study. The ATSDR has summarized many of the past scientific research papers using data from the Michigan Long-Term PBB Study in their 2004 Toxicological Profile for PBBs. Its major conclusions are described below. Between 2004 and 2009, while the Department was still managing the Long-Term PBB Study, additional research was done, and those published findings are also summarized below.
There is some evidence linking high amounts of PBB exposure in the Michigan Long-Term Study to an increased risk of cancers of the breast and the digestive system, as well as lymphoma. The number of cases is too few to make strong conclusions (ATSDR 2004, Terrell et al. 2016), though. These study participants had increased rates of health effects on the nervous system, immune system, skin, and musculoskeletal system. These effects did not show a consistent relationship with PBB amounts in the blood (ATSDR 2004). Some people who worked at the St. Louis chemical factory who breathed in and had skin contact with PBBs developed acne (ATSDR 2004).
Research identified no link between Michigan Long-Term Study participants with PBB exposure and benign breast disease and length of breast milk production (ATSDR 2004), infertility (Small et al. 2011), abnormal Pap tests (Jamieson et al. 2011), low birth weight of children (Givens et al. 2007), endometriosis (Hoffman et al. 2007), diabetes (Vasiliu et al. 2006), or thyroid problems (Yard et al. 2011). Women enrolled in the Michigan PBB Long-Term Study with high initial PBB amounts in the blood along with a recent weight loss (suggesting the possible release of stored PBBs in the body) seemed to have a shorter menstrual cycle but menstruated for a longer time during their period (Davis et al. 2005). There was some evidence that women in the study gave birth to slightly more boys than average (Terrell et al. 2009). Some of these boys had higher rates than expected of hernias and hydroceles (fluid collection in the scrotum) (Small et al. 2009).
The study showed that PBBs can be passed from an exposed mother to her children via breast milk (ATSDR 2004, Joseph et al. 2009). The study also showed that the female children breastfed by mothers who had been highly exposed to PBBs started menstruation at a slightly younger age than expected (Blanck et al. 2000). There is some evidence that spontaneous abortion (miscarriage) rates were increased, but only among second-generation women in the Long-Term Study who were born after the Michigan PBB incident (Small et al. 2011).
The Michigan Long-Term PBB Study was the basis of many years of scientific research. The study formally closed in 2004. MDHHS discontinued any further activity in 2009 to update study records or start new research with the study cohort. Since that time, the department has directed people interested in PBB research to Emory University’s PBB study. MDHHS is helping Emory University form their PBB study. However, Emory’s study includes a wider range of people than just those who were part of the MDHHS’ Michigan Long-Term PBB Study.