Is current generation of polychlorinated biphenyls exceeding peak production of the 1970s?

Polychlorinated biphenyls (PCBs) are man-made chemicals that were once widely produced as commercial mixtures for various industrial applications. PCBs were later recognized as environmental pollutants and health hazards, leading to their global phase-out and strict regulations on their production, use, and disposal. Most investigations on PCBs focus on measuring the specific PCBs present in commercial mixtures or marker compounds representing those mixtures. However, there are new sources of PCBs that are gaining more attention. These 'by-product PCBs' are inadvertently produced in certain chemical and product formulations. Our estimates show that U.S. legislation currently permits the generation of more by-product PCBs (~100 million lb. (~45,000 Tonnes) per year) than during peak commercial production of the 1970s (85 million lb. (~39,000 Tonnes) per year). These PCBs are currently going un-detected in most investigations. Therefore, they may be a posing a growing, unmonitored environmental and human health risk. Most people assume PCBs to be legacy pollutants from historically formulated commercial mixtures. However, our research suggests that due to the emergence of by-product PCBs they may need to be reconsidered as an emerging pollutant of concern.

Polychlorinated biphenyl (PCB) half-lives in humans: A systematic review.

This manuscript presents a systematic review of PCB half-lives reported in the scientific literature. The review was completed in accordance with PRISMA guidelines and included a review of almost 1000 peer-reviewed publications. In total, 26 articles were found to report half-lives in humans, with the majority of data coming from studies performed in North America on individuals suspected to have been exposed to PCBs. Terminology for reporting PCB half-lives was inconsistent, so we have attempted to consolidate this and recommend using either "apparent half-life" or "intrinsic half-life" in future studies. Within the literature, values for reported half-lives varied considerably for different PCBs. Less chlorinated PCBs generally have shorter half-lives than more chlorinated PCBs. It was interesting to note the large variability of half-lives reported for the same PCB. For example, the reported half-life for PCB 180 varied by nearly 3 orders of magnitude (0.34 years-300 years). Our review identified that the half-lives estimated were largely dependent on the studied cohort. We discuss the importance of PCB body burden, degree of chlorination and PCB structure, gender, age, breastfeeding, BMI, and smoking status on half-life estimations. We also identified significantly shorter half-lives for some PCBs in occupationally exposed individuals compared to results reported from the general population. PCB half-lives are not the same for every PCB or every individual. Therefore, careful consideration is needed when these values are used in human exposure studies.