Time trends of persistent organic pollutants in the atmosphere over the Indian Ocean in the last 30 years

An expedition around the Indian Ocean by sailboat (Jocara Indian Ocean Quest) in 2004/5 provided a novel and unusual opportunity to collect air samples for the analysis of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs). The region of the Indian Ocean, and its bordering countries are considered to be a prime source of the global atmospheric POPs. Concentrations of the industrial compounds PCBs were in the range of 6.8 to 114.3 pg m(-3). Hexachlorocyclohexane (HCH) and dichlorodiphenyl-trichloroethane (DDT) were the dominant OCPs and concentrations ranged between 2.4 and 105.6 pg m(-3), and between 2.5 and 33.2 pg m(-3) respectively. Data were compared with those reported for the mid-1970's and beginning of the 1990's to identify temporal trends in atmospheric POP levels over Southeast Asia and the Indian Ocean. Data comparision shows that concentrations of OCPs have declined significantly, by a magnitude of two, since the mid 1970's, but were highest at the beginning of the 1990s. The trend of atmospheric PCBs is less apparent.