Because of these factors PBTs have been observed to have a high order of bioaccumulation and biomagnification, very long retention times in various media, and widespread distribution across the globe.
[1] PBTs may have a high environmental mobility[clarification needed] relative to other contaminants mainly due to their resistance to degradation (persistence).
The low degradation rates of PBTs allow these chemicals to be exposed to both biotic and abiotic factors while maintaining a relatively stable concentration.
[3] The bioaccumulative ability of PBTs follows suit with the persistence attribute by the high resistance to degradation by biotic factors, especially with in organisms.
[3] The toxicity of this class of compounds is high, with very low concentrations of a PBT required to enact an effect on an organism compared to most other contaminants.
This high toxicity along with the persistence allows for the PBT to have detrimental effects in remote areas around the globe where there is not a local source of PBTs.
Due to extensive concern from the public, legal, and scientific sectors indicating that PCBs are likely carcinogens and potential to adversely impact the environment, these compounds were banned in 1979 in the United States.
[4] The ban included the use of PCBs in uncontained sources, such as adhesives, fire retardant fabric treatments, and plasticizers in paints and cements.
[4] The inclusion of PCBs as a PBT may be attributed to their low water solubility, high stability, and semi-volatility facilitating their long range transport and accumulation in organisms.
[6] The toxicological interactions of PCBs are affected by the number and position of the chlorine atoms, without ortho substitution are referred as coplanar and all others as non-coplanar.
[2] Correlations have been found between elevated exposure to PCB mixtures and alterations in liver enzymes, hepatomegaly, and dermatological effects such as rashes have been reported.
[5] One PBT of concern is DDT (dichlorodiphenyltrichloroethane), an organochlorine that was widely used as an insecticide during World War II to protect soldiers from malaria carried by mosquitoes.
[16] Lastly, the most common transport route is the evaporation of DDT into the atmosphere followed by condensation and eventually precipitation where it is released into environments anywhere on earth.
[17] Due to the long-range transport of DDT, the presence of this harmful toxicant will continue as long as it is still used anywhere and until the current contamination eventually degrades.
[19] This inhibition of closing the sodium ion channel can lead to a variety of problems including a dysfunctional nervous system, decreased motor abilities/function/control, reproductive impairment (egg-shell thinning in birds), and development deficiencies.
Inorganic mercury has a wide spectrum of toxicological effects that include damage to the respiratory, nervous, immune and excretory systems in humans.
[25] The global distribution of organic mercury is the result of general mobility of the compound, activation via bacteria and transportation from animal consumption.
In 1965, it was recognized that extensive mercury pollution by the Chisso chemical factory in Minamata, Japan due to improper handling of industrial wastes resulted in significant effects to the humans and organisms exposed.
[21] Harbor seals (Phoca vitulina), a common marine species in the Puget Sound area, have been the focus of a few studies to monitor and examine the effects of DDT accumulation and magnification in aquatic wildlife.
[21] Both animal and human health risk to DDT will continue to be an issue in Puget Sound especially because of the cultural significance of fish in this region.