2,2',3,3',4,4',5,5',6-Nonabromobiphenyl

EYES: irrigate opened eyes for several minutes under running water. INGESTION: do not induce vomiting. Rinse mouth with water (never give anything by mouth to an unconscious person). Seek immediate medical advice. SKIN: should be treated immediately by rinsing the affected parts in cold running water for at least 15 minutes, followed by thorough washing with soap and water. If necessary, the person should shower and change contaminated clothing and shoes, and then must seek medical attention. INHALATION: supply fresh air. If required provide artificial respiration.

The exact mechanism of toxicty of PBBs varies depending on the specific congener. The predominant interaction is believed to involve the aryl hydrocarbon receptor (AhR). PBBs bind to and activate the AhR, which in turn initiates the transcriptional upregulation of a number of genes, affecting biochemical and endocrine pathways, cell cycle regulation, morphogenesis, oxidative stress response, and various other processes. This results in the numerous toxic responses characteristic of PBBs. Some of the known induced genes include the cytochrome P-450-dependent monooxygenases CYP1A1 and CYP1A2. (L628)

PBBs can be absorbed via oral, inhalation, and dermal routes. Due to their lipophilic nature, PBBs, especially the highly brominated congeners, tend to accumulate in lipid-rich tissues such as the liver, adipose, skin, and breast milk. Certain PBB compounds are metabolized by the microsomal monooxygenase system catalyzed by cytochrome P-450 of the type induced by phenobarbital. The rate of metabolism may depends on the bromine substitution pattern. PBB congeners of low bromine content are transformed into hydroxylated derivatives that are predominately eliminated in the urine. Highly brominated congeners are either retained or excreted unchanged in the feces. (L628)

PBBs can be used as flame retardants and may be added to the plastics used to make products like computer monitors, televisions, textiles, and plastic foams to make them difficult to burn. However, the use of PBBs is banned or restricted in most areas due to their toxicity and persistence in the environment. (L628, L629)