This week our team wanted to do something slightly difference for our bi-weekly blog post: we’re going to take a step away from PCBs and discuss issues regarding other toxins we’ve mentioned in previous posts, including – are you ready for this word? – Dichlorodiphenyltrichloroethane (DDTs), as well as Polycyclic Aromatic Hydrocarbons (PAHs), dioxins, and other Persistent Organic Pollutants (POPs).
To answer your first question, no we will likely never use that full word ever again. “DDTs” works just fine, however there is a saying in the chemistry world: “the more syllables it has, the worse it is.”
To answer the question of, “what are these and how are they related to PCBs and what you guys do at ecoSPEARS?” Well, readers, we’re very glad you asked. There’s a bit of ground to cover, so stick with us.
While PCB molecules have many different formations (hence the prefix “poly” in their name), all of them share two characteristics: all are made up of one or two six-sided biphenyl molecules to which are attached anywhere from 4-10 chlorine atoms. The following picture shows several different examples of possible PCB molecular structures.
PCBs are able to assume many chemical forms due to their versatility and stability.
Now let’s look at an outline of the standard DDT molecule.
The DDT molecule, color coordinated to help explain its chemical structure. Notice the abundance of Chlorine atoms.
Notice any distinct similarities between DDTs and PCBs? The phenyl molecules are a giveaway. DDTs also have chlorine atoms spawning from their phenyl rings, as well as the hydrogenated bond connecting the phenyls together.
DDT was once a commonly used pesticide popular for its effectiveness to eliminate agricultural and household pests. Its properties as a pesticide also made it a popular chemical to use in the prevention of diseases such as malaria and even bubonic plague in countries around the world. DDT was manufactured and used for nearly thirty years in the United States before it was banned in 1972 due to public outcry for the potential risks it posed to humans and the environment. DDT, much like PCBs, are known carcinogens, chlorine-based, and highly hydrophobic allowing them to persist naturally in the environment for years with no natural way to mitigate or remove it.
Much of the outcry on DDT came after the publishing of Silent Spring in 1962 by Rachel Carson, which led to the founding of the US Environmental Protection Agency and the national ban of DDT. It is also credited for kickstarting the modern environmental activism movement.
The inspiration for Carson’s book came from a letter sent to her by her friend Olga Owens Huckins, who also sent the letter to The Boston Herald. In the letter, Huckins described the deaths of various birds around her property which she believed to be attributed to the spraying of DDT.
Huckins’s hunch wouldn’t be far off at all. In the decades to come, environmental scientists studied the affects of DDT on various bird species, including the Peregrine Falcon, California Condor, and Bald Eagle whose populations were by then already dwindling. What they found was indeed a correlation between the spraying of DDT and a thinning of egg shell walls in these bird species. The thin walls of the egg prevent the embryo of the chick from fully developing which led to a great number of these unborn birds perishing prematurely, drastically lowering their numbers in the wild.
Decades later we are finally seeing a resurgence in some of the bird species once affected by DDT poisoning.
The US is far from the only country to have long-lasting problems with DDT. A 1998 paper published in the International Journal of Epidemiology showed the results of various studies in concentrations of DDT in the breast milk of women around the world and spanning nearly 50 years, from 1950 until 1996.
The results are shocking primarily for two separate reasons: 1) the concentration levels spike as high as 76,800 micrograms of DDT per kilogram in the breast milk fat of rural Guatemalan women in 1971, and 2) because the decrease in DDT concentrations over time in the breast milk of American and Western European women show a trend in the data that lead scientists to believe DDT – like PCBs – tend to bioaccumulate and pass from mother to child.
Today, the production and use of DDT is banned worldwide due to the knowledge we now possess of its effects to human health and our ecosystem.
Next, let’s move onto PAHs. Similar to PCBs, PAHs are organic chemical compounds which are able to take on different structures while retaining the same basic properties. The simplest aromatic hydrocarbon molecule is commonly known as benzene.
A benzene molecule, often referred to by chemists as an “honorary” PAH.
Although not technically a PAH due to its singular ring, scientists often consider benzene an “honorary PAH” as it also allows chemists to generalize the chemical structure of PAHs with two or more hexagonal rings consisting entirely of carbon atoms.
The molecule’s entire makeup consists solely of carbon and hydrogen, hence the term “hydrocarbon.” Benzene’s aromatic nature comes from its carbon-carbon skeleton, which interestingly enough makes it much more physically stable comparatively to other hydrocarbon molecules. Benzene is commonly studied by astrochemists and astrophysicists because its structural integrity allows it to survive the harsh void of space. This is because PAHs, “are very easily formed in high temperature (+/- 2,000 K) carbon and hydrogen rich gases.”
Gases abundant in carbon and hydrogen are commonly found in emissions and discharge from burning fossil fuels such as coal, wood, and oil.
Various PAH molecules. Similar to PCBs, the structural integrity of these chemicals allows them to persist in nature.
All of these various forms of PAHs change into another when one or more hydrogen atoms are lost as these molecules fly around within the released high-temperature gas and collide. Hydrocarbon molecules become more reactive the more hydrogen atoms they lose, making them more likely to pick up extra carbon molecules and form a different PAH.
While the chemistry of PAHs is fascinating, the chemical’s persistence and effect on human health and ecology is less so. The Agency for Toxic Substances & Disease Registry (ATSDR) explains that PAHs pose health risks to our skin tissue, liver, and immune system. PAHs have also been proven to cause tumor growth and cancer in humans exposed to them for long periods of time.
Similar to PCBs and DDT, PAHs are not water-soluble and can persist in lake or river beds, marine sediment, and groundwater. Because PAHs are not chlorinated compounds such as DDT or PCB, this allows microorganisms to be able to break down the organic structure of PAHs over time, although many PAHs produced and released into the environment years – if not decades – ago remain.
The chemical nature of PAHs allows them to latch onto solid particles in the air and travel along wind currents, making PAHs a much more prominent POP threat to communities and ecosystems downwind of large manufacturing and power plants which release heavy amounts of PAHs via exhaust.
Now, onto the last POP chemical we’re covering in our blog post today: Tetrachlorodibenzodioxin. Otherwise known much more simply as “dioxin.”
A dioxin molecule. Many dioxins and PCBs share striking chemical similarities.
This picture shows the typical dioxin molecule. With our brief lesson in chemistry from the beginning of this post, you can notice the four chlorine atoms (“tetra-chloro”) at the ends of the molecule immediately make it a contender for POP just as nasty as DDT and PCB. As with PAHs, dioxins’ chemical structure makes them extremely stable and difficult to break down. WHO estimates the half-life for dioxin in the body to be between 7-11 years, but “in the environment, dioxins tend to accumulate in the food chain. The higher an animal is in the food chain, the higher the concentration of dioxins.”
The same, as we’ve said before in our posts, is true for PCBs.
In fact, because of similarities in the chemical makeup of PCBs and dioxin, there are several PCBs which are known to be “dioxin-like,” rendering them potential candidates for us to remediate using the SPEARS technology. While a silver lining, it should be noted that this is due to the highly toxic and persistent nature of dioxins to accumulate and exist in the natural world. Contamination from dioxins, as with PCBs, more often than not hits harder in communities that played no part in their production or spread. Some, thankfully, are able to stop the spread of contamination before it has a chance to affect their communities.
Ireland recalled tons upon tons of pork meat in 2008 when some meat samples were found to contain amounts of dioxins hundreds of times higher than what it said to be the “safe” limit. Nearly a decade prior, high dioxin levels were found in poultry meat and eggs from Belgium. In both cases, the dioxins were traced back to contaminated animal feed and was stopped before it had a chance to be ingested by the human population.
Others, however, are not always so lucky, especially in decades prior when public knowledge and safety measures were not as widespread or ensured as they are today. A chemical cloud containing TCDD, a known dioxin, contaminated roughly 15 square kilometers of land after being released from an accident at a factory in Seveso, Italy in 1976. The contamination is estimated to have affected some 37,000 people. Many of those affected underwent lifelong testing in order to determine long-term affects of dioxin exposure to humans.
If the acronym TCDD rings a bell to you, that’s because it should. TCDD was also a contaminant present in some batches of the chemical otherwise known as Agent Orange used during the Vietnam War. Half a century later, scientists are still studying and determining the long-term effects to human health, including diabetes and various types of cancer, which come as a result of exposure to this chemical.
A famous picture from the Vietnam War – a lone child stands among charred mangrove husks defoliated by Agent Orange.
If you aren’t sitting here right now and asking yourself, “wait…why are we allowing toxic chemicals from Agent Orange to seep into our food, water, and wildlife?” You should be.
The key takeaway from all these toxic POPs is, despite being banned decades ago, their presence lingers. Not in one or two hotspots, but globally. Each one of the chemicals we’ve outlined in this post poses adverse effects to human health and wildlife. All of them have been studied and shown to possess enough toxic features that, if unchecked, they could potential cause shift to an entire ecosystem.
One of the very reasons the Bald Eagle – the US national bird – was endangered for so long was due to poisoning from DDT preventing embryos from maturing and hatching. Since the outlawing of DDT in America, Bald Eagle numbers have soared once again from a sobering 500 back towards 70,000.
The Peregrine Falcon – the fastest recorded animal in the world with top speeds of 240 mph – has also seen a resurgence in US numbers over the last 40 years. In 1964, there wasn’t a single Peregrine recorded to be living east of the Mississippi River. As of 2015, the US Fish and Wildlife Service places their population closer to nearly 4,000 nesting pairs.
It could be said (perhaps more poetically by someone else) that the climbing numbers of these birds’ populations is a symbol – a metaphor of sorts – for the values that ecoSPEARS represents. Our team and our organization exist to give our waterways a second chance on life. We seek to aim high, but just as trees grow from the ground up, we cannot forget our roots or the thousands upon thousands of communities across the United States and the rest of the world we seek to help. Nor do we allow the trivial things to block our path along the way. There is always a solution, especially when more people seek to become a part of it.
It can be done. Despite the fact that it will likely take many, many years to accomplish.
Just as it took many, many years for the Peregrine Falcon population to boom once more.
But today, the largest gathering of Peregrine Falcons in the United States is found in New York City. Soaring high above the Hudson River.
A Peregrine Falcon flying over the Verrazano Bridge in The Bronx, NYC. (source: MTA, State of New York)
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For more information on how you can help America’s bird populations grow, please see the following links:
Want to learn more about ecoSPEARS? Our technology can help your community clean PCBs, PAHs, dioxins, and other contaminants from water and soil.
Email our team to let us know where we can help!
Read our study done with NASA and Golder Associates.
Read about the first ever field study done with SPEARS technology.
Interested in meeting our team? ecoSPEARS will be attending the following conferences and trade shows:
March 6-7, 2018: Emerging Contaminants Summit The Westin Westminster 10600 Westminster Blvd., Westminster, CO, 80020
April 8-12: Conference on Remediation of Chlorinated and Recalcitrant Compounds Palm Springs Convention Center 277 North Avenida Caballeros Palm Springs, CA, 92262
August 22-24, 2018: Georgia Environmental Conference Jekyll Island, GA