From here, I would like to talk about toxic assessment of dioxin-related compounds.

Most of toxicities of dioxin-related compounds is occurred through this pathway.

After dioxin-related compounds enter to cell, they bind on Aryl hydrocarbon receptor. And then, this complex enter to nucleus, regulate various DNA, and elicit the toxic effects.

Because all dioxin-related compounds elicit their toxic effects through this pathway, toxic values of these chemicals are conversed to toxic values of 2378-TCDD, which have the highest toxicity among dioxin-related compounds.

This toxic value is called TEQs (2378-TCDD toxic equivalents).

For conversion of toxic values, toxic equivalency factors (TEFs)of dioxin-related compounds are set using relative binding affinity on aryl hydrocarbon receptor to that of 2378-TCDD.

TEQ in soil is calculated using this formula.

 

This shows the TEQs found in soils from Malaysian dumping sites. X-axis indicates the location and sample no., and y-axis shows TEQs.

Relatively high TEQs were found in soils from dumping site in Selangor with levels at 3,100 pg/g and 510 pg/g on dry wt. These are exceeded the environmental and monitoring standard set by Japanese government.
This indicates mass formation of dioxin-related compounds during combustion of waste.
And these high value are requested that combustion of wastes should be stopped and soils in these dumping site are need to be cleaned.

TEQs in soils from Kedah dumping site are ranged from 7.8~48 pg/g on dry wt. These in Penang are 10~16pg/g.

Interestingly, TEQ in soils from controlled dumping site in KL was the lowest, and they were comparable or lower than background level.

These results suggest that in Malaysian dumping site, emission of dioxin-related compounds can be decreased with management of waste treatment. It means combustion of waste should be stopped.

 

I would like to explain why emission controls of PCBs, PCDDs and PCDFs are need not only in developed countries, but also in tropical and subtropical Asia.

This shows the estimated flux of PCDD/DFs to soil in dumping sites from Asian developing countries, in comparison with those in soils from developed nations.

In this case, Flux indicates how many PCDD/DFs are formed per same size of area and time. So, high value indicates the mass formation of PCDD/DFs.

General speaking, formation of PCDD/DFs may be apparently lesser in developing countries than in developed nations.

However, As you can see here, Flux to soils from Asian dumping sites were extraordinarily great, when compared to those from developed nations, indicating mass formation of PCDD/DFs in dumping sites from Asian developing countries.

Thus, this result clearly suggests that dumping sites in developing countries are played as one of the greatest sources of PCDD/DFs.

This problem is not only in developing countries, but also on global scale, because of specific climate in tropical and subtropical Asia.

 

This is model of migration process of POPs.

Due to high temperature and heavy rain, POPs, which entered into tropical and subtropical environment, are evaporated into air or flowed by water. And then, these contaminants are migrated on global scale. Finally, they are gone to open sea and polar region, where are played as final sink of these contaminants.

 

This is an example data indicating the contamination levels are relatively high in open ocean, although no contamination source is available here.

This shows the concentrations of PCDFs and mono-ortho coplanar PCBs in the birds from open oceans and Japan.
Terrestrial species shows the green bar, costal species blue bars and birds inhabiting open oceans shows red bars.

If POPs are not migrated and contaminated only surrounding fields of sources, the highest levels is found in terrestrial birds, followed by coastal species. And open ocean birds retained the lowest concentrations.

However, these two species, which inhabit in open oceans, retained comparable concentrations of PCDFs and mono-ortho coplanar PCBs to terrestrial birds.

Similar patterns have been reported on other POPs, such as PCBs and organochlorine pesticides. And this pattern are also reported in other biota and environmental media.

Thus, if emission controls of dioxin-related compounds, PCBs and other POPs, are done only in few countries, these action are not perfect for conserving environment on global scale. All the countries should be cooperated to reduce POPs levels.

I would like to conclude the present study.

First conclusion is that Dioxin-related compounds were detected from all the soil samples from dumping site in Malaysia.

Second is that The highest concentration was found in dumping site, where was found combustion of waste, indicating recent formation of PCDD/DFs.

Final conclusion is that Soils from controlled dumping site retained DXNs at comparable levels to control site (Lake Garden), suggesting that emission of these chemicals can be decreased with management of waste treatment.

Because PCBs and its related compounds, PCDDs and PCDFs, have persistent and bioaccumulative nature, several decades are need for degradation of these contaminants in environment and biota.

In addition, these chemicals are easily transportable from surrounding area of pollution sources to worldwide.

Considering these with high toxicity, further investigation and emission control of PCBs, PCDDs and PCDFs are urgent subjects for conserving future environment and for comfortable life of next generation.

My presentation is over. Thank you for your attention.