Know it, to control it

Vehicular exhausts and lung cancer

Pollution from motor vehicles is an environmental health problem of modern times around the world. As population increases globally, the number of vehicles being bought are also increasing. Exposure to motor vehicle emissions is so widespread in urban environments that it is difficult to measure differing degrees of lifetime exposure to such emissions.

In India, chest specialists are seeing a dramatic increase in lung cancer and chest diseases and cite exposure to vehicular exhausts as one of the main causes. Multiple reports carried out on animals and humans have confirmed a direct link between exposure to diesel engine emissions and lung cancer.

The association with diesel exhaust was strongest for squamous cell tumors, a pattern similar to that for cigarette smoking.

The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), classifies diesel engine exhaust as “carcinogenic to humans,” based on sufficient evidence of the link to an increased risk of lung cancer.

The National Toxicology Program (NTP) in the USA was formed from parts of several different government agencies, including the National Institutes of Health (NIH), the Centre for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA).

The NTP has classified exposure to diesel exhaust particulates as “reasonably anticipated to be a human carcinogen,” based on evidence from studies in humans mainly linking it to lung cancer. Furthermore, the National Institute for Occupational Safety and Health (NIOSH), a part of the CDC that studies exposures in the workplace has determined that diesel exhaust is a “potential occupational carcinogen.”

There has been a shift from gasoline- to diesel-powered engines in many industries over the past 5-6 decades. Diesel is a type of fuel now used in most large engines, including trucks, buses, trains, construction and farm equipment, generators, ships, and in some cars. Diesel exhaust is made up of gases and soot (particles). Gases include carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, sulfoxides, and hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), known carcinogen. The soot (particulate) contain carbon, organic materials (including PAHs), and traces of metallic compounds. Exhaust from diesel engines is present on the roads, cities, farms, and many other places where people can be exposed to diesel exhaust.

Several studies of workers exposed continuously to diesel exhaust have shown significant increases in the risk of lung cancer. Truck drivers, toll booth workers, miners, and other heavy machinery operators have a high exposure because of their occupation. However, equally high exposure has been reported in buildings along major highways and in cities. At least 140 million people in India live in heavily polluted areas and are breathing air 10 times the WHO safe limit of10 micrograms of particulate matter 2.5 per cubic meter.

The children in close proximity to vehicle polluted areas are at a much higher risk of chest diseases including asthma and chronic lung disease as the particulate pollutant settle down and children being of shorter height inhale these pollutants.

Taking all the evidence together, the India government is in the process to provide for strict fuel and emission norms for vehicles by 2020.