Around twenty years ago, large numbers of spawning coho salmon in the United States’ West Coast were mysteriously dying. Upon investigation, it was discovered that the most probable culprit is a toxic chemical from tires that is released in the environment through tire dust. Tire wear particles, or TWP, are emitted continually as vehicles travel. When it rains, TWP are washed into waterways.
The toxic chemical is called 6PPD-quinone or 6PPD-q. When 6PPD, a chemical added to tires to prevent their cracking and degradation, is exposed to ground-level ozone, it’s transformed into multiple other chemicals, including 6PPD-q. The compound is acutely toxic to four of 11 tested fish species, including coho salmon. Could 6PPD-q be one of the reasons too why there are fewer fish in our rivers today?
While this chemical is known to be toxic to fish, no study has been done so far on its effect on humans. It’s been detected in the urine of children, adults, and pregnant women in South China. It is possible that jeepney and tricycle drivers, and even commuters, are exposed to TWP and possibly to 6PPD-q. Same is true with houses and other establishments who are located along busy roads.
British firm Emissions Analytics, which has spent three years studying tire emissions, found that a car’s four tires collectively emit one trillion ultrafine particles per kilometer driven. These particles, a growing number of experts say, pose a unique health risk. They are so small they can pass through lung tissue into the bloodstream and cross the blood-brain barrier or be breathed in and travel directly to the brain, causing a range of problems.
According to a recent report issued by researchers at Imperial College London, “There is emerging evidence that TWP and other particulate matter may contribute to a range of negative health impacts including heart, lung, developmental, reproductive, and cancer outcomes.”
Tire rubber contains hundreds of chemicals and compounds, some of them carcinogenic. Tires are made from natural rubber and synthetic rubber plus hundreds of other ingredients, including steel, fillers, and heavy metals like copper, cadmium, lead, and zinc. The additives are to enhance performance, improve durability, and reduce the possibility of fires.
Unlike the smoke coming out of the tailpipes of vehicles, there is no law regulating TWP in the Philippines or in other countries. However, in Europe, a standard to be implemented in 2025, known as Euro 7, will regulate not only tailpipe emissions but also emissions from tires and brakes. The California Environmental Protection Agency has passed a rule requiring tire makers to declare an alternative to 6PPD-q by 2024.
Meanwhile, it may be a good practice to continue wearing facemasks when riding in an open vehicle. For houses along busy highways or roads, planting trees will help filter tire dust and other particulates. For vehicle owners and drivers, proper wheel alignment, correct tire pressure and good driving habits will help reduce tire wear and thus lessen tire dust.