Persistent organic pollutants (POPs) are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Under typical windspeeds, a chemical can travel 150-800 km in two days and result in contamination in remote locations (Scheringer, 2009). Estimated atmospheric gas-phase reaction half-lives of POPs (Table 5.1) range from less than one day to greater than a year.
Groundwater is one of the easiest ways to tell how the environment is reacting to different types of pollutants. While organic pollution occurs naturally, inorganic pollution is a result of some human interaction or doing (such as fluoride in the water supply which is used to help teeth health).
They include pesticides such as DDT and lindane, industrial chemicals such as polychlorinated biphenyls (PCBs), and substances such as dioxins, which are the unwanted by-products of manufacturing and combustion processes.
Most POPs (persistent organic pollutants) (these will soon be considered as persistent toxic substances or PTS) are organochlorine pesticides, namely, aldrin, endrin, clordane, DDT, heptachlor, mirex, toxaphene and hexachlorobenzene.
Domestic wastes (garbage), urine, faecal matter, sewage, agriculture residues, paper, wood, cloth, cattle dung, animal bones, leather, wool, vegetable stuff or plants are biodegradable pollutants.
Under the Clean Air Act, the National Ambient Air Quality Standards (NAAQS) are developed by the Environmental Protection Agency (EPA) for six common air pollutants, also called "criteria pollutants": particulates; smog and ground-level ozone; carbon monoxide; sulfur oxides; nitrogen oxides; and lead.
Metals, such as lead, mercury, and arsenic, are always persistent, since they are basic elements and cannot be further broken down and destroyed in the environment. Although this discussion will focus on synthetic organic chemicals the potential health effects of exposure to metals should not be overlooked.
The “dirty dozen” are the pesticides aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex and toxaphene; the industrial chemicals PCBs and hexachlorobenzene; and combustion by-products dioxins and furans.
So, although it is not persistent in the same way that some other organic pollutants are, the frequent and con- tinuous applications of glyphosate in rural and urban settings make its presence ubiquitous (Mesnage et al. 2015).
Releases to soil can evaporate into the atmosphere or run off into water bodies. There are not thought to be any natural sources of DDT to the environment. It is also highly persistent in the environment - and is therefore classed as a persistent organic pollutant (POP).
What should consumers do to reduce their risk of exposure? Trimming fat from meat and consuming low fat dairy products may decrease the exposure to dioxin compounds. Also, a balanced diet (including adequate amounts of fruits, vegetables and cereals) will help to avoid excessive exposure from a single source.
DDT was last imported into the United States in 1972, when imports amounted to 200 tons. Although the use of DDT was banned in the United States after 1972, it was still manufactured for export. Presently, there are no producers of DDT in the United States, and therefore, there are no exports of DDT.
Environmental persistence is an important property that can enhance the potential of a chemical substance to exert adverse effects and be transported to remote environments. Assessing the persistence of chemical substances in the environment is not straightforward.
Nonpersistent pesticideDefinition A pesticide whose harmful effects are of relatively short duration and, therefore, do not normally contaminate the environment for long periods after application.
The group of chemicals known as polychlorinated biphenyls (PCBs) is one of the original twelve POPs covered by the Stockholm Convention. However, existing equipment that contains or is contaminated with PCBs may continue to be used until 2025.
Aromatic hydrocarbons including benzene, toluene, ethyl benzene, xylene (BTEX) and polyaromatic hydrocarbons (PAHs) are persistent organic pollutants (POPs), released into the environment mainly by exploration activities of petroleum industry.
StrawberriesFor four years running, strawberries have topped the EWG's Dirty Dozen list. According to USDA data collected from 2015 to 2016, conventionally-grown strawberries contained far more pesticide residues than other fresh produce, even after rinsing.
DDT (dichloro-diphenyl-trichloroethane) was developed as the first of the modern synthetic insecticides in the 1940s. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations.
The "dirty dozen" chemicals banned in an international treaty are formally known as persistent organic pollutants, or POPs. The United Nations Environment Program provided this background on what they are and what they can do to humans and wildlife.
Polychlorinated biphenyls
Persistent organic pollutants (POPs) are well known environmental pollutants, of which the most well-known are dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs).
Growing concern about adverse environmental effects, especially on wild birds, led to severe restrictions and bans in many developed countries in the early 1970s. The largest agricultural use of DDT has been on cotton which accounted for more than 80% of USA use before its ban there in 1972.
Production, use, and managementDDT is currently being produced in three countries: India, China, and the Democratic People's Republic of Korea (DPRK; North Korea) (Table 1). By far the largest amounts are produced in India for the purpose of disease vector control.
Substances
- Fossil Fuels.
- Organic Chemicals.
- Particulate Matter.
- Polycyclic Aromatic Hydrocarbons.
- Vehicle Emissions.
DDT (dichloro diphenyl trichloroethane) is a non- biodegradable pesticide. It is persistent, fat soluble and shows biomagnification.
In many parts of India, DDT is ineffective. Agricultural uses were banned in 1989 and its anti-malarial use has been declining. DDT can still be effective against resistant mosquitoes and the avoidance of DDT-sprayed walls by mosquitoes is an additional benefit of the chemical.
Dioxins and polychlorinated biphenyls (PCBs) are toxic chemicals that persist in the environment and accumulate in the food chain. Dioxins have no technological or other use, but are generated in a number of thermal and industrial processes as unwanted and often unavoidable by-products.
