Contamination is due to the spillage of the defoliant ‘Agent Orange’. The Vietnamese Ministry of National Defence found an average dioxin level of about 35,000 ppt TEQ at former US airbases Da Nang, Bien Hoa, and Phu Cat.
Source categories of waste contamination by POPs:
Polychlorinated dibenzo-p-dioxins
and dibenzofurans (dioxins)