The here presented study gives a rough impression of the PCDD/Fs and DL PCB air concentrations in the close vicinity of the Map Ta Phut Industrial Estate, Thailand. It is not possible to determine a clear spatial gradient as only 3 samples were taken. There are no legal standards defined for POP concentrations measured in air by PAS, thus a comparison of the found concentrations with PAS determined PCDD/Fs and DL PCBs levels elsewhere was conducted. The Map Ta Phut DL PCBs levels are similar to South Korean urban residential sites and PCDD/Fs levels are an order of magnitude lower than at various South Korean sites including rural and industrial. PCDD/Fs and DL PCBs concentrations found in Map Ta Phut are also similar to levels at African urban sites and do not indicate an extremely serious pollution level as in e.g. industrial areas of Cairo, Egypt. However, it is important to consider that the sampling in Map Ta Phut was conducted at sites with an accumulation of vulnerable parts of the general population (children at the Wat Map Chalut School and patients at the Map Ta Phut Hospital) or at a site of spiritual importance (Wat Nong Faeb Temple). Unfortunately, the sampling was not conducted in the respiration height (approximately 1.5 m above ground) but higher in order to allow for free airflow around the PAS.
Concentrations of PCDDs/Fs in Africa determined by PAS measurements are similar to concentrations reported for Europe based on active air sampling (Bogdal et al., 2013). However, PAS determined PCDD/Fs levels probably underestimate the real occurrence of these POPs in air, as PUF PAS do not sample PCDD/Fs with complete efficiency due to the incomplete sampling of the atmospheric particulate fraction (Markovic et al., 2015). Thus it is not possible to suggest that Map Ta Phut PCDD/Fs air concentrations are similar to European levels because they are similar to African urban levels. On the contrary, it is reasonable to anticipate real PCDD/Fs air concentrations in Map Ta Phut to be higher than reported in this study and thus higher than in Europe. This drawback does not apply for DL PCBs, as these occur predominantly in the gas-phase (Trinh et al., 2018) and differences between active and passive air sampling should be much less pronounced.