You’ve probably smelled it, the overpowering, nostril-burning stench when new coal-tar pavement or sealant is being laid on a driveway, street, parking lot or playground. And you may have idly wondered how toxic the shiny black liquid spray might be, but moved on to other things because, after all, what can you do about it?
As it turns out, it is toxic. The substances contain polycyclic aromatic hydrocarbons (PAHs).
One recently released study by the Geological Survey identified coal-tar sealants as the primary source of PAHs and called them ‘a major source of contamination in urban and suburban areas and a potential concern for human health and aquatic life.’
The problem finally made headlines when toxic coal-tar sealants were found to be responsible for up to 94 percent of the PAHs found in 40 samples of stream bed sediment, aka muck collected from 19 creeks and rivers, along with dust from six parking lots.
According to lead study author and GS scientist Austin Baldwin, “All 78 percent of the samples contained enough PAHs to be considered toxic and capable of causing adverse effects in aquatic animals.”
How it happens is fairly straightforward. Over time, PAHs and other contaminants from sealed and blacktopped surfaces wash into storm water storage basins and storm sewers from rain and melting snow. From there, the toxins are washed straight into the closest waterways, essentially poisoning them.
Coal-tar sealants used for paving in commercial, residential and industrial areas are preferred by many due to aesthetic reasons. However, they contain up to 1,000 times more PAHs than asphalt emulsions, which do a comparable job but cost more.
Besides the toxic materials used to build roadways and other surfaces, similar issues are emerging. Another new study says storm water runoff is so poisonous, it can kill an adult coho salmon in just 2.5 hours.
The study also reveals a costly consequence of regulations requiring developers to excavate storm water storage basins next to massive parking lots. PAHs cling to dirt, sand and other particles in the storm water that settles to the bottom of the basins.
Coal tar, a byproduct of converting coal to coke is a solid-carbon fuel and carbon source for the steel-making industry, and it’s a known human carcinogen. As coal is heated to produce coke, coal tar vapors are released.
A study in 2013 found that PAHs in area streams were worse for aquatic life than other chemicals.
The study showed that PAHs pose a very real threat to aquatic organisms at the base of the food chain. Among the adverse effects are fin erosion, liver abnormalities, cataracts and immune system damage. Exposure to the chemicals also can cause high rates of tumors in fish.
In fact, research on salmon killed by runoff began more than a decade ago. Projects to restore the salmon’s habitations had brought a slow but steady stream of coho back to urban streams, but many died before they could spawn, notably right after rainstorms, including 90 percent of the females.
A story is told, of a 27-year-old man who was admitted in a Hospital for the Insane in April of 1887. Less than two weeks later, another man showed up in similar condition.
Then a third showed up. It turned out they all worked at the same rubber factory. Knowing it couldn’t be a coincidence, an investigation ensued.
The culprit causing the men’s bizarre, incoherent and erratic behavior, according to the chief of the Nervous Department of Physicians and Surgeons, was carbon disulfide, a colorless liquid that evaporates rapidly at room temperature and was linked to some acute insanity cases.
Connecting the dots, one study shows carbon disulfide to be a solvent in manipulating PAH materials.
Carbon disulfide was invented as a means to render rubber pliable enough to make tires using a process called vulcanization. To forego the necessary heating process in huge factories, this solvent treated rubber in a cold vulcanization process for superior wear and probably hundreds of uses.
It’s impossible to say how many people today have benefited from this discovery, billions of users of rubber products, from shoe soles to hoses to tires while a lower but not insignificant number suffer because of it.
A doctor, Paul Blanc, who chairs the department of occupational and environmental medicine at the University of California, described carbon disulfide as a “very unique toxin; in its manifestations, truly protean,” meaning unpredictable in its effects to the nervous system as well as birth defects and interference with menstruation.
Some of them are quite startling, especially its capacity to cause insanity, but also atherosclerosis in the heart and the brain, as well as Parkinsonism. His investigation found mention of the toxin as early as 1849, along with warnings to workers in regard to its vapors.
Century-and-a-half-old evidence seemed ample warning to producers that this substance wasn’t something to mess with. One researcher in 1856 noted everything from weird dreams to memory gaps; premature aging to ‘abolished’ sexual desire. Ironically, many victims worked in condom factories.
One man in particular, a ‘sober, tranquil’ individual, worked in the rubber industry for 17 years. When he began cleaning vulcanization vats containing carbon disulfide, he had a bad reaction, diagnosed with ‘toxic hysteria’ from carbon disulfide poisoning. He first experienced an acute burning sensation in his scrotum and then collapsed on the job, fully anesthetized. He was unconscious for half an hour and bedridden for two days, which were filled with nightmares and hallucinations of ‘terrible animals’. He did not recover fully, but remained weak and given to twitching.
While carbon disulfide isn’t in tires anymore, it’s still a problem. A study in 2014 cited an ‘unnamed’ plastic and rubber manufacturing plant where workers exposed to carbon disulfide between 1946 and 2006 had more than double the rate of fatal heart disease compared to other workers. However, it’s used in other industries, sometimes referred to as fake silk or viscose.
Farmers have also used it liberally to fumigate grains and kill gophers and other plants for ‘skinless’ sausage casings and sponges. The manufacturing process is potentially harmful to workers exposed to it via air pollution, as the carbon disulfide levels in the air are 50 percent higher in urban than rural areas.
While scientists say it might be dangerous, many countries still spread roads with brine from oil and gas operations, believing it’s a safe way to recycle it. But the wastewater is tainted, not just with chloride+, but radium and barium, which are radioactive. While they’re not from fracking, the toxins are similar.
The usage of road salt has been found to damage food sources for insects. In higher concentrations, it can kill amphibians as well as plants.
Experts believe that salt spread onto roads would be washed into storm drains and dissipate without causing much of a problem. They didn’t realize it could build up in soil alongside roads, creating a salt bank and cause worse trouble and for a longer time than first thought.
Over time, chronic salt concentrations can damage algae that are food sources for the insects eaten by local fish, but in high concentrations, the salt can kill amphibians and plants and leach into wells where people get their drinking water. As it is, more than 20 million tons of salt are thrown onto roads every year in most developing countries in Africa.
What Can Be Done and What’s Being Done
In the Pacific Northwest, scientists had a bad feeling about the potential of toxins from run-off for a long time, but the salmon study opened a door that would allow them to not just study the problem but help fix it. They created a simple, soil-based filtration system.
In 2013, scientists concerned about road toxicities got creative to alleviate the problem and came up with a few innovative solutions: free cheese brine, sugarcane molasses, and beet juice, mixed in with road salt to act as alternate de-icing agents.
Julann Spromberg, Ph.D., a toxicologist for the Oceanic and Atmospheric Administration and co-author of the coho salmon study, said that in many cases, all that can be done for many of these problems is to basically let the Earth do what it does so well, what it has done for eons: clean things up.