Polybrominated Biphenyl - Health Hazards

Health Hazards

Exposure to the coplanar stereoisomer 3,3',4,4',5,5'-hexabromobiphenyl (but not the non-coplanar stereoisomer) in genetically susceptible mice is known to cause immunotoxicity and disorders related to the central nervous system, and even at doses as low as 2.5 mg/kg, excess neonatal fatalities are observed (LD₅₀ is from 5–10 mg/kg). The mechanism of toxicity is cellular oxidative stress by aryl hydrocarbon receptor activation.

There is evidence that pre- and post-natal exposure to PBB in girls leads to menarche at an earlier age.

Early studies on the effects of PBBs on human beings concerned the people in Michigan, USA who consumed PBB-contaminated animal products (see history of PBBs below). A study of 327 girls aged 5–24 years in Michigan found those who were exposed in utero to PBBs at or above a level of 7 ppb found had an earlier age at menarche compared to a case-control group. Michigan dairy farmers exposed to PBBs had significant immune system abnormalities including reduced numbers of circulating blood lymphocytes, increases in lymphocytes with no detectable surface markers, and reduced functional response to specific test antigens. Some residents complained of nausea, abdominal pain, loss of appetite, joint pain and lethargy, though it could not be clearly established that PBBs were the cause of these health problems. Workers who were exposed to PBB during PBB production suffered hypothyroidism, although no deterioration in memory performance was found in PBB-exposed workers in tests conducted several years after final PBB exposure, and there was also no correlation of performance with PBB concentration.

There is stronger evidence that PBBs may have caused skin problems, such as acne, in consumers of the contaminated food. Some workers exposed to PBBs by breathing and skin contact for days to months also developed acne.

Studies in animals exposed to large amounts of PBBs for a short period or to smaller amounts over a longer period show that PBBs can cause weight loss, skin disorders, nervous and immune systems effects, as well as effects on the liver, kidneys, and thyroid gland.