The toxicity associated with PCBs and other chlorinated hydrocarbons, including polychlorinated naphthalenes was recognized very early due to a variety of industrial incidents.[9] A conference about the hazards was organized at Harvard School of Public Health in 1937, and a number of publications referring to the toxicity of various chlorinated hydrocarbons were published before 1940.[10] Robert Brown reminded chemists in 1947 that Arochlors were "objectionably toxic. Thus the maximum permissible concentration for an 8-hr. day is 1 mg/m3 of air. They also produce a serious and disfiguring dermatitis".[11] However, PCB manufacture and use continued with few restraints until the 1970s.
PCBs are persistent organic pollutants and have entered the environment through both use and disposal. The environmental transport of PCBs is complex and nearly global in scale. The public, legal, and scientific concerns about PCBs arose from research indicating they were likely carcinogens having the potential to adversely impact the environment and therefore undesirable as commercial products. Despite active research spanning five decades, extensive regulatory actions, and an effective ban on their production since the 1970s, PCBs still persist in the environment and remain a focus of attention.[2]
Zoologist and author Desmond Morris dies aged 98
Trump, like many great Presidents, has provided words to inspire
