Polycyclic Aromatic Hydrocarbons (PAH)

What are false solutions? The International Rights of Nature Tribunal defines them as “solutions which pretend to address the key issues while in reality only perpetuating this unsustainable status quo.” They include CCS, which allows for heavy industry to continue to be dependent on combusting fossil fuels rather than switching to renewable energy and feedstocks. It also includes marine scrubbing, which allows for the shipping industry to continue to burn fossil fuels to power their ships. One of the unsustainable aspects of the status quo of shipping is the release of pollutants into the air and water, including PAH.  

Polycyclic aromatic hydrocarbons (PAH) are a class of over 100 chemicals present naturally in fossil fuels, and are also produced when fossil fuels, wood, or tobacco are burned. PAH are also formed when grilling or smoking meats. Many PAHs are carcinogens (cancer-causing), mutagens (DNA damaging), or teratogens (cause birth defects). Although PAH are not emitted in large quantities by industrial sources in St. James Parish, LDEQ data shows about 1600 tons of PAH were emitted across Ascension, St. John, and St. Charles Parishes. 

Exposure to PAH can happen in several forms. Breathing air that is contaminated with PAH, such as cigarette smoke, car exhaust, or industrial pollution, can cause lung cancer. PAHs can be ingested through food- while grilled/smoked meat is the largest source of concern, plants do uptake PAH from contaminated soils. Eating food contaminated with PAH can increase the risk of prostate, colon, or breast cancers. Finally, 

Because PAH can bioaccumulate in the body, it is important to address existing pollution as well as prevent more emissions. When PAHs break down, they form derivative chemicals that can be many times more carcinogenic than the original PAH. PAH in our oceans are a serious pollution concern. A study of seabed sediment around ports found high levels of PAH levels, which have been deposited there through decades of burning PAH containing fossil fuels in ports. As discussed in the Chemical of the Month on NOx, recent trends towards electrification of ports will help prevent more PAH from being deposited as ships turn to “plugging in” to the grid rather than burning fossil fuels while at port.

However, even as port PAH emissions into the air are diminishing, marine scrubbing is perhaps causing even more damage than PAH emissions. Marine scrubbers spray seawater onto a ship’s exhaust to transform the gas exhaust into a liquid- a liquid which still contains all the pollutants present in the fossil fuel exhaust. While scrubbers do reduce emissions of pollutants like sulphur and PM2.5 into the atmosphere, these pollutants get transferred to the scrub water and are released into the ocean. About 85% of scrubbers in use are open loop, meaning that the water is directly discharged into the marine environment without being treated. Releasing scrubber water into the ocean not only adds pollutants like PAH to the water, but because it can be 100,000 times more acidic than seawater, releasing it decreases the ocean pH (makes the ocean more acidic). Ocean acidification is a serious problem that threatens the life of the ocean as we know it, with special harm to coral reefs and shellfish that cannot form reefs or shells in acidic water. 

Scrubbers only exist because of a loophole allowing ships to keep burning heavy fuel oil if they install scrubbers to “reduce” the pollution into the atmosphere (see the Chemical of the Month on nickel for more information about HFO). Unfortunately, what seemed like a good plan to reduce air pollution has seriously impacted the oceans. Exposure to PAH has caused cancer in whales. Plankton, the building block of life in the ocean, die if exposed to scrubber wastewater even in low concentrations. A better solution could be to make closed-loop scrubber systems mandatory, where the pollutants in the wastewater are collected and later disposed of in a landfill. In the meantime, ships with open loop scrubbers could also be prohibited from dumping their wastewater in protected areas or ports. It all comes back to fossil fuels- while there are many false solutions like marine scrubbing, CCS, and chemical recycling that seek to prolong the use of these fuels, the only way we have forward is to find real solutions that protect life on our planet.

HOW TO REDUCE YOUR EXPOSURE TO PAHS:

• While delicious, grilled and smoked meats are major sources of PAH, which contribute to the carcinogenic nature of foods like hot dogs and salami. Baking or stewing meat does not produce nearly as many PAHs. If you do grill, using a marinade can reduce PAH formation, as can cooking on an aluminum tray. 
• Cigarette smoke is the main form of PAH exposure for most people, including high levels in secondhand smoke. 
• When cooking at high heat, run an exhaust fan or open windows.   
• Some anti-dandruff shampoo contains coal tar; these shampoos can contain PAHs which are absorbed by the skin.