Friday, October 24, 2014

You can’t sense it…

This is the pollution that you can't feel by using any of the five senses. If you are overexposed to it, it might work as a timed bomb in your body and you might not know when the detonation is occurring. 
Yes, it is radioactivity. 

What is radioactive material and radioactive decay?

All materials are made of atoms. Radioactive atoms are unstable (have too much energy). Radioactive decay is the release of extra energy by radioactive atoms. The energy is called ionizing radiation may take the form of alpha particles (a), beta particles (b), or gamma rays (g). (Fentiman, Leet, & Meredith)

Electromagnetic Spectrum Illustration. See text below.
Figure 1 Types of Radiation in the Electromagnetic Spectrum
Source: (Ionizing & Non-Ionizing Radiation, 2013)

Non-ionizing radiations:
  • electromagnetic waves of longer wavelength
  • energies enough to excite the atoms and molecules of the medium through which they are moving, causing them to vibrate faster

Ionizing radiations:
  • electromagnetic radiations of short wavelength (high energy)
  • energetic rays like (a, b and g etc.) produced in radiocative decay can cause ionization of atoms and molecules of the medium through which they pass and convert them into charged ions

After releasing all the excess energy, the atoms become stable and are no longer radioactive. (Fentiman, Leet, & Meredith)

Radioactive Pollution

Living organisms are continuously exposed to a variety of radiations called background radiations.If the level of the radioactive radiations increases above a certain limit it causes harmful effects to living beings. This harmful level of radiations emitted by radioactive elements is called radioactive pollution. (RADIOACTIVE POLLUTION)

Anthropogenic Sources of Radiation
  • Diagnostic medical applications: e.g. X-rays are used in general radiology and CT scan
  • Nuclear Tests: nuclear explosion detonated for either military or peaceful purposes (carried out for non-military purpose, such as the construction of harbours and canals) (WORLD OVERVIEW)
  • Nuclear Reactors: Radiations may leak from nuclear reactors and other nuclear facilities even when they are operating normally. It is often feared that even withthe best design, proper handling and techniques; some radioactivity is routinely released into the air and water. (RADIOACTIVE POLLUTION)

Route of exposure to radiation

Figure 2 Environmental fate and human exposure of radiation
Source: (International Advisory Committee, 1991)

The environmental fate of radioactive material is quite similar to POPs as mentioned in the previous blog post, except that radioactive material emits energy. Radioactive material is suspended in air at a height of 6 to 7 km above the earth’s surface and is dispersed over long distances by winds from the test site. These radionuclides often settle down by rain and get mixed with soil and water. From there they can easily enter the food chain and finally get deposited in the human body where they cause serious health hazards. (RADIOACTIVE POLLUTION)

What happens to radiation produced?

Nuclear waste is categorized into different level:

Types of nuclear waste

Low level waste (LLW)
  • Contain small amounts of mostly short-lived radioactivity
  • Sources: hospitals, industry, nuclear fuel cycle
  • Examples: contaminated  clothing such as protective shoe covers, paper and plastics

Intermediate level waste (ILW)
  • contains higher amounts of radioactivity
  • reactor water  treatment residues and filters used for purifying a reactor’s cooling water

High level waste (HLW)
  • highly radioactive and hot
  • two distinct kinds of HLW:
spent fuel from reactors
o   Separated waste from reprocessing the used fuel

Table 1 Different types of nuclear waste
Source: (Getting to the Core of Radioactive Waste)(Radioactive Waste Management, 2014)

Different countries might have different practices and regulations for the storage and disposal of different levels of nuclear waste. 

Generally, low level radioactive gases and liquids are release into the environment under controlled, monitored conditions to ensure that they pose no danger to the public or the environment. This is due to the fact that these releases dissipate into the atmosphere or a large water source and, therefore, are diluted to the point where it becomes difficult to measure any radioactivity. By contrast, most of an operating nuclear power plant's direct radiation is blocked by the plant's steel and concrete structures. The remainder dissipates in an area of controlled, uninhabited space around the plant, ensuring that it does not affect any member of the public. (Frequently Asked Questions (FAQ) About Radiation Protection, 2012)

Practices to handle LLW/ ILW:
  • stored on-site by licensees, either until it has decayed away and can be disposed of as ordinary trash, or until amounts are large enough for shipment to a low-level waste disposal site (Backgrounder on Radioactive Waste, 2014)
  • transported to a central treatment facility
  • burnable waste is incinerated at a central site (Management of Low and Intermediate-level Radioactive Waste (The), 1989)
  • disposed of closer to the surface, in many established repositories.  Low-level waste disposal sites are purpose built, but are not much different from normal municipal waste sites (What are nuclear wastes and how are they managed?)
Low and Intermediate waste store

Figure 3 Low-level and Intermediary-level waste (LLW/ILW) repository
Source: (What are nuclear wastes and how are they managed?)

Practices to handle HLW:
  • Used fuel will still contain some of the original U-235 as well as various plutonium isotopes. Countries such as Europe and Russia separate uranium and plutonium from the wastes so that they can be recycled for re-use in a nuclear reactor.
  • Storage ponds at reactors which are often designed to hold all the used fuel for the life of the reactor
  • Future possibility: 'multiple barrier' geological disposal is planned to ensure that no significant environmental releases occur over tens of thousands of years (disposal). Waste will be immobilized waste in an insoluble matrix, seal it inside a corrosion-resistant container and locate it deep underground in a stable rock structure. (Radioactive Waste Management, 2014)
THORP Fuel Storage

Figure 4 Storage pond for used fuel
Source: (Radioactive Waste Management, 2014)

Controversies of discharging radioactive material into the environment

In the late 1940s, the nuclear industry had chosen the open ocean as a convenient place to dispose of its inconvenient wastes. In 1972, a global treatry called the London Dumping Convention had banned the dumping of high-level radioactive wastes. However, it was not effective due to the classification of radioactive wastes as high, medium, or low-level  by International Atomic Energy Agency (IAEA) was for handling purposes (for the protection of workers) and had little to do with the radio-toxicity and the isotopic composition of radioactive wastes. Low-level radioactive wastes, could also be found extremely radio-toxic and persistent isotopes.

In 1980s, nuclear industry recognized that radioactive waste dumping on the seabed was banned, so they claimed that dumping under the seabed was not banned. Nuclear industry from various countries equipped with drilling gear and/or suppository-shaped free-fall penetrators (containers which would penetrate the seabed like armour piercing bullets) ships from these countries would shoot the high-level wastes under the seabed. This was more serious than dumping on the seabed because it was impossible to monitor. In the event of leakage, the radioactive wastes would be irretrievable.

In November of 1993, the Contracting Parties to the London Convention (later of London Dumping Convention) adopted amendments banning the dumping of radioactive wastes based on the fact of “the diffusibility of the waste radionuclides in sea water which could result in transboundary transfer of these radioactive materials” as well as the “comparative difficulty of monitoring radioactive waste packages dumped at sea”. (Parmentier, 1999)

In 1996, the 1996 Protocol eventually replace the London Convention entered into forced in 2006), represented a major change of approach to question how to use the sea as a depository of waste material. It restricts all dumping except some permitted substances. (Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other )

The permitted substances containing levels of radioactivity greater than de minimis (exempt) concentrations as defined by the International Atomic Energy Agency (IAEA) and adopted by Contracting Parties, shall not be considered eligible for dumping. (1996 PROTOCOL TO THE CONVENTION ON THE PREVENTION OF MARINE POLLUTION BY DUMPING OF WASTES AND OTHER MATTER, 1972 , 2006)

This means that LLW or ILW might be eligible to dump into the sea provided that it is lower than the concentration defined by IAEA. This is the reason for many countries to discharge their LLW intot the ocean.

However, it seems that there might be some loopholes in the 1996 Protocol. For example, thousands of tons of radioactively contaminated water from the damaged Fukushima Daiichi nuclear power plant were pouring directly into the ocean. On April 4, 2011, some three weeks after the initial disaster, the Tokyo Electric Power Co. (TEPCO), with the Japanese government’s consent, decided to release 10,000 tons of “low-level radioactive water” to make room in its storage facilities for the huge volume of more highly contaminated water that had been used for emergency cooling of the damaged Dai-ichi reactors. (Pacchioli, 2013)

Japan utilizes the loophole that 1996 Protocol prohibits ocean dumping of radioactive material, limits these restrictions to vessels at sea. One of the definition of “dumping” in 1996 Protocol is “any deliberate disposal into the sea of wastes or other matter from vessels, aircraft, platforms or other man-made structures at sea”. (1996 PROTOCOL TO THE CONVENTION ON THE PREVENTION OF MARINE POLLUTION BY DUMPING OF WASTES AND OTHER MATTER, 1972 , 2006)
Hence, release of materials from land is not considered dumping.

Recently, even UN nuclear watchdog had advised the Fukushima Daiichi nuclear power plant to consider dumping toxic water (controlled discharge) into the ocean after lowering the level of radioactive materials to below the legal limit. (IAEA suggests Fukushima consider ‘controlled discharge’ of toxic water into ocean, 2013)
Beside this legal issue, the contamination might affect marine life and human. Although the ocean has the capacity to dilute nuclear contamination, signs of spreading radioactive material are being found off Japan, including the discovery of elevated concentrations of radioactive cesium and iodine in small fish several dozen miles south of Fukushima, and high levels of radioactivity in seawater 25 miles offshore.

Two events in the early 1990s — a die-off of seals in the Barents Sea and White Sea from blood cancer, and the deaths of millions of starfish, shellfish, seals and porpoises in the White Sea — have been variously attributed by Russian scientists to pollution or nuclear contamination. These suggested that these marine lives had been expose to radioactive or other toxic substances. Hence, the dilution capacity might not be totally safe. (Grossman, 2011)

Currently, the effect on marine ecosystem is unclear since no records are yet available on the exact composition of the radioactive refuse and no one knows for sure if containment vessels are intact or leaking. (TED Case Studies Arctic Sea Dumping)

Works Cited

1996 PROTOCOL TO THE CONVENTION ON THE PREVENTION OF MARINE POLLUTION BY DUMPING OF WASTES AND OTHER MATTER, 1972 . (2006). Retrieved October 24, 2014, from International Maritime Organization:
Backgrounder on Radioactive Waste. (2014, June 27). Retrieved October 24, 2014, from US Nuclear Regulatory Commission:
Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other . (n.d.). Retrieved October 24, 2014, from International Maritime Organization:
Fentiman, A. W., Leet, T. A., & Meredith, J. E. (n.d.). What Is Radioactive Material and How Does It Decay? Retrieved October 24, 2014, from Ohio State University:
Frequently Asked Questions (FAQ) About Radiation Protection. (2012, December 11). Retrieved October 24, 2014, from US Nuclear Regulatory Commission:
Getting to the Core of Radioactive Waste. (n.d.). Retrieved October 24, 2014, from International Atomic Energy Agency:
Grossman, E. (2011, April 7). Radioactivity in the Ocean: Diluted, But Far from Harmless. Retrieved October 24, 2014, from Yale Environment 360:
IAEA suggests Fukushima consider ‘controlled discharge’ of toxic water into ocean. (2013, December 4). Retrieved October 24, 2014, from RT NEWS:
International Advisory Committee. (1991). THE INTERNATIONAL CHERNOBYL PROJECT TECHNICAL REPORT. Retrieved October 24, 2014, from International Atomic Energy Agency:
Ionizing & Non-Ionizing Radiation. (2013, May 17). Retrieved October 24, 2014, from US Environmental Protection Agency:
Management of Low and Intermediate-level Radioactive Waste (The). (1989, August). Retrieved October 24, 2014, from Nuclear Energy Agency:
Pacchioli, D. (2013, May 6). Seafood Safety and Policy. Retrieved October 24, 2014, from Woods Hole Oceanographic Institution:
RADIOACTIVE POLLUTION. (n.d.). Retrieved October 24, 2014, from National Institute of Open Schooling:
Radioactive Waste Management. (2014, September). Retrieved October 24, 2014, from World Nuclear Association:
TED Case Studies Arctic Sea Dumping. (n.d.). Retrieved October 24, 2014, from American University:
What are nuclear wastes and how are they managed? (n.d.). Retrieved October 24, 2014, from World Nuclear Association:
WORLD OVERVIEW. (n.d.). Retrieved October 24, 2014, from Comprehensive Nuclear-Test-Ban Treaty Organization:

Friday, October 17, 2014

SOS, it's POPs!

Remember we have talked about DDT in the previous post? We are going to shift our focus to the “big family” of DDT which is the Persistent Organic Pollutants (POPs).

POPs are resistant to chemical degradation, giving them long half-lives in the environment. This long-lived organic contaminants biomagnify in food chains and may ultimately cause toxic effects. Biomagnification refers to chemical concentrations is higher in higher trophic level organisms and exceed those concentrations in the organism’s prey.

This is a review on a study investigated the extent to which various organic chemicals biomagnify in lichen, caribou, wolf food chains of Canada’s Arctic tundra region. (KELLY & GOBAS, 2001)

Figure 1 Illustration on the studied food chain

Chemical input to the tundra ecosystem is from atmospheric sources, resulting in gaseous partitioning between air and lichens, particulate (dry) deposition, and wet deposition (e.g., snow). Chemical uptake by lichens can occur from air-lichen equilibrium partitioning when directly exposed to the air, or from water-lichen exchange during exposure to melting snow. Following chemical uptake in lichens, the transport of contaminants in the food chain is controlled by biomagnification processes in caribou and wolves.

The reason to choose these species is because the food web structure in the studied region is approximately linear (lichens à caribou à wolves). Lichens and willow are the dominant food source to caribou and caribou is the dominant food for wolves. Hence, it is more representative to investigate the ability of contaminants to biomagnify in terrestrial food chains.

Concentrations of several hydrophobic organic contaminants in lichens, caribou, and wolves were collected and. Concentrations were then expressed in terms of fugacities and compared by applying the statistical methods. Fugacity is most often regarded as the "escaping tendency" of a chemical from a particular phase. (Appendix P Earthworm Fugacity Estimation )In this study, fugacity is used to express the concentration of chemical.

Figure 2 Sampling Locations

During the spring of 1997 (i.e., May-June), Cl.rangiferina and Ct. nivalis samples were collected east and west of Bathurst Inlet along the Huikitak and Hood Rivers, respectively. During the summer of 1998 (i.e., July), additional samples of Cl. rangiferina and Ct. nivalis east and west of Bathurst Inlet were obtained near the communities of Omingmaktok (east) and Brown Sound (west), while at Cambridge Bay only Ct. nivalis samples were collected.

Figure 3 Fugacities of lichens and willows
Data are presented on log scales. Error bars represent the standard deviation. ND indicates nondetectable concentrations during chemical analysis. An asterisk (*) indicates statistical significance difference (p < 0.05) between mean chemical fugacities in lichens collected in spring (Huikitak and Hood River samples) as compared to lichens collected nearby in summer (Omingmaktok, Brown Sound, and mid-Bathurst samples). Two asterisks (**) indicate a statistically significant difference (p < 0.05) between vegetation species at a given sampling location.

Bioaccumulation in Lichens
The result showed that fugacities of organochlorines such as α-HCH, γ-HCH, and HCB were greater than fugacities of PCBs (congener 153) in vegetation samples at all sampling locations. At some locations, samples of Ct. nivalis, Cl. rangiferina, and S. glauca exhibited statistically different fugacities of α-HCH,  γ-HCH, HCB, and PCBs (e.g., Inuvik, Brown Sound, and Cambridge Bay). There were no statistically significant differences in fugacities of α-HCH, γ-HCH, HCB, and PCBs in lichens and willow leaves collected during the summer. This indicates that the spatial distribution of these contaminants is fairly homogeneous, possibly reflecting atmospheric concentrations. The available data indicate that differences in chemical concentrations among the various food items in the caribou diet are small during summer months.

PCB congeners demonstrated comparable fugacity increases in spring-collected lichens relative to lichens collected during summer. This might be due to accumulation of these substances in spring meltwater and subsequent uptake in lichens. Collection of lichen samples in the spring of 1997 occurred during the spring snowmelt period. Snowpacks contain contaminants scavenged during the previous winter’s snowfall events. Snow sublimation tends to “concentrate” these contaminants in the snowpack; especially for low volatile PCBs evaporate very slowly while the more volatile HCHs and HCB evaporate more rapidly, reducing their degree of snowpack accumulation. During snowmelt events, when snow turns into meltwater, a significant drop in the fugacity capacity may further elevate the fugacity in meltwater over that in the snowpack. 

Figure 4 Fugacities (nPa) of individual compounds from various classes of POPs in food chains
Data are presented on log scales, where bars represent the chemical fugacities in lichens Cl. Rangiferina and Ct. nivalis in summer, caribou during fall (males and females), and wolves during fall (males and females). The left-hand scale is for HCHs and chlorobenzenes (CBz). The right-hand scale is for DDTs, PCBs, and chlordanes. Error bars represent the standard deviation. ND indicates nondetectable concentrations during chemical analysis. An asterisk (*) refers to statistically significant biomagnifications for the lichen-caribou trophic transfer (i.e., fCARIBOU > fLICHEN), while two asterisks (**) represent statistically significant biomagnifications for the caribou-wolf transfer (i.e., fWOLF > fCARIBOU).

Bioaccumulation in Barren-Ground Caribou:
Predominant compounds detected in caribou tissue samples were α-HCH, β-HCH, 1,2,4,5-TCB, HCB, oxychlordane, p,p’-DDE, and PCB congeners 118, 138, 153, and 180. The fugacities of chlorobenzenes (1,2,4,5-TCB and HCB) and HCHs (α and β isomers) were greater than those of PCB congeners and organochlorine pesticides. Fat concentration data were used to represent the fugacities in caribou for the biomagnification analysis because higher chemical concentrations in fat tissue was tested, which imply smaller analytical error than liver and muscle tissues.

The fugacities of HCHs, DDTs, chlordanes, chlorobenzenes, and PCBs in the tissues of male caribou from Bathurst Inlet were significantly greater in the summer than in the fall. The observed drop in chemical fugacities between the summer and the fall can be explained by increased lipid production and growth. In the Arctic, caribou gain substantial deposits of fat and protein over the short summer period to utilize energy during the winter, resulting in greater body weights in the fall as compared to early summer. This tends to “dilute” the chemical concentration in the fat.

Bioaccumulation in Wolves
α-HCH, β-HCH, 1,2,4,5-TCB, HCB, oxychlordane, and PCB congeners 153, 138, and 180 were the predominant compounds observed in wolf tissues.

Biomagnification of POPs in Lichen-Caribou-Wolf Food Chains:
Hexachlorocyclohexanes (HCHs)
  • β-HCH appears to biomagnify in the food chain as indicated by an increase in fugacity with each trophic level. The fugacities of β-HCH in wolves were significantly greater than those in caribou at all three locations.
  • No substantial biomagnifcation or trophic dilution of α-HCH was observed. α-HCH fugacities were not statistically different between lichens, caribou, and wolves.
  • The fugacity of γ-HCH is shown to decrease with increasing trophic level, indicating trophic dilution, probably due to metabolic transformation.
  • Both caribou and wolves can efficiently eliminate γ-HCHand to a smaller extent β-HCH but not α-HCH.

  • No biomagnification of HCB was observed in Cambridge Bay male wolves.
  • 1,2,4,5-TCB biomagnified in wolves from Bathurst Inlet and Inuvik but not in wolves from Cambridge Bay
  • Food chain bioaccumulation of 1,2,4,5-TCB was only observed at Bathurst Inlet due to nondetectable levels of this compound in either lichens or caribou samples from Cambridge Bay and Inuvik.
  • fugacities of PCB 153 and 180 increase significantly with increasing trophic level
  • fugacities of PCB 52 were not statistically different between trophic levels, suggesting that relative to PCB 153 and 180, PCB 52 is eliminated and/or metabolized efficiently in both caribou and wolves

  • Technical grade chlordane, a pesticide mixture consists mainly of chlordane (cis and trans), heptachlor, and nonachlor (cis and trans) compounds.
  • Oxychlordane is the predominant metabolite of chlordane and nonachlor compounds. Hence, extensive biomagnification of oxychlordane in relation to chlordane and nonachlor components indicates metabolic transformation of technical chlordane.
  • Oxychlordane biomagnified in the caribou wolf trophic transfer at all three locations while transnonachlor only biomagnified in Bathurst wolves.

  • the fugacity p,p’-DDT (DDT related compound) in caribou was significantly lower than that in lichens, indicating the ability of caribou to metabolize p,p’-DDT
  • the fugacity of p,p’-DDE (DDT related compound) is shown to increase from lichen to caribou at Bathurst Inlet
  • data suggest that caribou may have the ability to metabolize or eliminate p,p’-DDT but not the persistent metabolite p,p’-DDE
  • Neither p,p’-DDT nor p,p’-DDE biomagnify in wolves, indicating these animals can metabolize both p,p’-DDT and p,p’-DDE

The two important parameters affecting POPs biomagnifications are gastrointestinal absorption efficiencies and lipid-to-air elimination rates in the animals, which are strongly dependent on the chemical’s KOW and KOA.
  • Octanol-Water Partition Coefficient (KOW) - A coefficient representing the ratio of the solubility of a compound in octanol (a non-polar solvent) to its solubility in water (a polar solvent). The higher to KOW, the more non-polar the compound. (Octanol-Water Partition Coefficient (KOW), 2014)
  • Octanol-air partition coefficient (KOA) - The "octanol-air" partition coefficient (KOA) characterizes POP partitioning between air and organic films. (Erdman, Gusev, & Pavlova, 1999)

Hydrophobic organic chemicals with high KOW can relatively easily pass through biological membranes via passive diffusion. When absorbed, organic chemicals are quickly distributed within the organisms and partition predominantly in the lipids. (CHAPTER 4 TOXICITY ASSESSMENT)

The significance of a high KOA for terrestrial biomagnification is that lipid-to-air elimination (through exhalation) is low, causing, in absence of metabolic transformation, a very low depuration rate to counteract uptake from the gastrointestinal tract, hence resulting in high tissue concentrations.

Different animal classes (e.g., herbivores and carnivores) are expected to exhibit differences in these two parameters due to their distinct taxonomic and physiological characteristics.

BMFs for individual animals can differ substantially with differences in gender, age, season, and dietary preference. Biomagnification factors (BMFs) is calculated as fB/fD, where fB is the fugacity in the higher level organism (e.g. wolves) and fD is the fugacity in the diet of the organism (e.g. caribou).

Note: All the information and figures in this post is extracted the journal "Bioaccumulation of Persistent Organic Pollutants in Lichen-Caribou-Wolf Food Chains of Canada’s Central and Western Arctic", unless they are cited with other resources.

Works Cited

Appendix P Earthworm Fugacity Estimation . (n.d.). Retrieved October 17, 2014, from US Environmental Proection Agency:
CHAPTER 4 TOXICITY ASSESSMENT. (n.d.). Retrieved October 17, 2014, from US Environmental Protection Agency:
Erdman, L., Gusev, A., & Pavlova, N. (1999, April). ATMOSPHERIC INPUT OF PERSISTENT ORGANIC COMPOUNDS TO THE MEDITERRANEAN SEA. Retrieved October 17, 2014, from Meteorological Synthesizing Centre - East:
KELLY, B. C., & GOBAS, F. A. (2001). Bioaccumulation of Persistent Organic Pollutants in Lichen-Caribou-Wolf Food Chains of Canada’s Central and Western Arctic. ENVIRONMENTAL SCIENCE & TECHNOLOGY , 325-334.
Octanol-Water Partition Coefficient (KOW). (2014, June 2). Retrieved October 17, 2014, from U.S. Geological Survey:

Friday, October 10, 2014

From Nobel Prize to Banned Chemical

Starting in the 1940's, the chlorinated hydrocarbon named DDT (dichloro-diphenyl-trichloroethane) was used in vast quantities all over the world for killing insects. It was cheaper and much more effective than other insecticides and kills nearly all insects. (Bryant, 2002)

DDT spray on beach
Figure 1 Spraying of DDT
Source: (The DDT Story)

DDT was then brought to the notice of British and American medical entomologists at a time, during World War II, when supplies of pyrethrum were rapidly falling short of demand. (Nobel Media AB, 2014) Pyrethrum affects the central nervous systems of all types of flying and crawling insects, disrupting normal function, so that nervous impulses fail. (Pyrethrum the natural insecticide, 2010)

Figure 2 Phyrethrum
Source: (Peirce, 2008)

Then, DDT was widely used during the Second World War to protect the troops and civilians from the spread of malaria, typhus and other vector borne diseases. After the war, DDT was continued to be used on a variety of agricultural crops and for the control of disease vectors as well. (6. SUBSTANCE PROFILES FOR THE PERSISTENT ORGANIC POLLUTANTS) 

DDT saved millions of lives by killing the mosquitoes that spread malaria and saved millions from starvation by killing crop pests. (Bryant, 2002) Paul Hermann Müller won The Nobel Prize in Physiology or Medicine 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods.". (Nobel Media AB, Paul Müller - Facts, 2014)

The heavy use of this highly persistent chemical, however, led to widespread environmental contamination and the accumulation of DDT in humans and wildlife - a phenomenon brought to public attention by Rachel Carson in her 1962 book, Silent Spring. (Persistent Organic Pollutants: A Global Issue, A Global Response, 2014)

Figure 3 Silent Spring by Rachel Carson

Silent Spring described how DDT entered the food chain and accumulated in the fatty tissues of animals, including human beings, and caused cancer and genetic damage. A single application on a crop, she wrote, killed insects for weeks and months, and not only the targeted insects but countless more and remained toxic in the environment even after it was diluted by rainwater. Carson concluded that DDT and other pesticides had irrevocably harmed birds and animals and had contaminated the entire world food supply. (The Story of Silent Spring, 2013)

Stockholm Convention on Persistent Organic Pollutants- a legally binding international agreement finalized in 2001. (Persistent Organic Pollutants: A Global Issue, A Global Response, 2014) Over 150 countries signed the Convention and it entered into force, on 17 May 2004. (The Stockholm Convention) The Convention aims to protect human health and the environment from the effects of persistent organic pollutants (POPs). The Convention has a range of control measures to reduce and, where feasible, eliminate the release of POPs, including emissions of unintentionally produced POPs such as dioxins. (Stockholm Convention on Persistent Organic Pollutants (POPs))

The Stockholm Convention established an initial list of 12 key POPs chemicals (the so-called dirty dozen) and DDT is one of them. (The Stockholm Convention) POPs are toxic chemicals that adversely affect human health and the environment around the world. They can be transported by wind and water, so they can affect people and wildlife far from where they are used and released. They persist for long periods of time in the environment and can accumulate and pass from one species to the next through the food chain. (Persistent Organic Pollutants: A Global Issue, A Global Response, 2014)

Properties of DDT:
  • highly insoluble in water and is soluble in most organic solvents.
  • semi-volatile and can be expected to partition into the atmosphere
  • lipophilic and partitions readily into the fat of all living organisms
DDT has been demonstrated to bioconcentrate and biomagnify. Due to its potential to spread widely and persistency, DDT is ubiquitous in the environment and residues have even been detected in the arctic. (6. SUBSTANCE PROFILES FOR THE PERSISTENT ORGANIC POLLUTANTS)

Bioaccumulation and Biomagnification of DDT in living organism:
  • DDT is not metabolized, and does not break down in the body.
  • It is much more soluble in fat than in water. So it accumulates in body fat and is not excreted.
  • The transfer of energy from lower trophic levels to higher ones is inefficient -so herbivores eat large quantities of plant material, and carnivores eat many times their body weight of prey during their lifetime. Since DDT is not excreted, the carnivore accumulates most of the DDT that was present in all of the prey organisms (Bryant, 2002)

Figure 4 Illustration on Bioaccumulation and Biomagnification
Source: (Hoop, 2013)

Large amounts of DDT were released into the air and on soil or water when it was sprayed on crops and forests to control insects. It may also enter the air when they evaporate from contaminated water and soil, then deposited on land or surface water again. This cycle of evaporation and deposition may be repeated many times and can be carried long distances in the atmosphere. (Public Health Statement for DDT, DDE, and DDD, 2011) Human still potentially expose to DDT by consuming contaminated fish and crops grown in the contaminated soil even though it was banned.  (DDT, 2011)

What are the harmful effects of DDT on human?
  • Probable human carcinogen
  • Damages the liver
  • Temporarily damages the nervous system
  • Reduces reproductive success
  • Can cause liver cancer
  • Damages reproductive system

The debate on DDT:
  • As the discussion of harmful effect brought by DDT, it seems that it is a wise decision to ban DDT. However, there are some “bring back DDT” claims.
  • “DDT is cheaper than other pesticides, more effective, and not harmful to human beings or animals.”
  • “Even where mosquito populations have developed resistance to DDT, it is more effective (and less problematic) than alternative chemicals. This is because replacement pesticides have to be applied more frequently and are more toxic”
  • “POPs Convention Is Genocide”
  • “Rachel Carson played on people’s emotions, and to do so, she selected and falsified data from scientific studies, as entomologist Dr. J. Gordon Edwards has documented in his analysis of the original scientific studies that Carson cited.”
  • “Mozambique stopped the use of DDT, because 80 percent of the country’s health budget came from donor funds, and donors refused to allow the use of DDT.”
(Hecht, 2002)

There are some people argued for the renewed use of DDT inside houses to fight the spread of malaria. They have pointed out; the standard environmental concerns -- such as eggshell-thinning in raptor birds -- have nothing to do with spraying indoors. Tiny amounts of DDT are used compared with the millions of pounds that were once sprayed on agricultural fields in the 1950s and 60s. The environmental consequences, as a result, would be negligible. (Avery & Avery, 2000)

Figure 5 Some people urged to bring back DDT
Source: (Hecht, 2002)

So, what is your stand? Should DDT be banned?

Lastly, here is an interesting and ironic statement about DDT:
“And its persistency, which is precisely what Müller was looking for, became one of the key problems.” As for Paul Müller, he died in 1965 – three years after the publication of Silent Spring. “He never complained that his compound which was a world saver was no longer in public favour.” (Landon, 2003)

Works Cited

6. SUBSTANCE PROFILES FOR THE PERSISTENT ORGANIC POLLUTANTS. (n.d.). Retrieved October 4, 2014, from United Nations Environment Programme (UNEP):
Avery, A., & Avery, D. (2000, July 28). Bring Back DDT, and Save Lives. Retrieved October 4, 2014, from THE WALL STREET JOURNAL:
Bryant, P. J. (2002). Chapter 14: HABITAT POLLUTION. Retrieved October 4, 2014, from School of Biological Sciences, University of California:
Hecht, M. M. (2002). Bring Back DDT, and Science With It! Retrieved October 4, 2012, from 21st Century Science and Technology Magazine:
Hoop, J. v. (2013, January 17). Bioamplification, Bioaccumulation and Bioconcentration. Retrieved October 4, 2014, from Mercury Science and Policy at MIT:
HOW SILENT SPRING BECAME NOISY SUMMER**. (2014, February 7). Retrieved October 4, 2014, from Project One Percent:
Landon, V. (2003, May 6). DDT: From miracle chemical to banned pollutant. Retrieved October 4, 2014, from swissinfo:
Nobel Media AB. (2014). Paul Müller - Biographical. Retrieved October 4, 2014, from Nobel
Nobel Media AB. (2014). Paul Müller - Facts. Retrieved October 4, 2014, from
Peirce, P. (2008, May 21). Pyrethrum-Based Insecticides from Chrysanthemums. Retrieved October 4, 2014, from Vegetable gardener:
Persistent Organic Pollutants: A Global Issue, A Global Response. (2014, June 12). Retrieved October 4, 2014, from United States Environmental Protection Agency:
Public Health Statement for DDT, DDE, and DDD. (2011, March 3). Retrieved October 4, 2014, from Agency for Toxic Substances and Disease Registry:
Pyrethrum the natural insecticide. (2010). Retrieved October 4, 2014, from Botanical Resources Australia Pty Ltd:
Stockholm Convention on Persistent Organic Pollutants (POPs). (n.d.). Retrieved October 4, 2014, from Department of the Environment, Australian Government:
The DDT Story. (n.d.). Retrieved October 4, 2014, from Pesticide Action Network North America:
The Stockholm Convention. (n.d.). Retrieved October 4, 2014, from UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION:
The Story of Silent Spring. (2013, May 12). Retrieved October 4, 2014, from Natural Resources Defense Council:
U.S. ENVIRONMENTAL PROTECTION AGENCY. (2011, April 18). DDT. Retrieved October 4, 2014, from Persistent Bioaccumulative and Toxic (PBT) Chemical Program: