When an engine burns diesel, the exhaust it releases contains substances that can potentially cause cancer and various other diseases. It is a mixture of particulates and gaseous materials of which 30 to 40 pose severe hazards; these include benzene, arsenic, nitrogen dioxide and some particulate matter.
This is something that has been widely researched around the world but not yet in Delhi, or anywhere in India. An international study, in fact, has found India would account for 10 per cent of all years of life lost worldwide due to exposure to vehicle emissions.
“Polycyclic hydrocarbons like diesel have been identified as chemical carcinogens globally,” said Dr P K Jhulka, professor of oncology and dean of academics at AIIMS. “Unfortunately, we don’t have any Indian research to correlate diesel with incidence of cancer. In the US, Australia and European countries, there have been several studies correlating exposure to diesel fumes and cancer risk.”
According to a 2009-11 report (released 2013) of 25 population-based cancer registries with the Indian Council of Medical Research, lung cancer was the most common cancer in men (10-12 per cent) and the sixth most common cancer among Delhi’s women. Dr Jhulka, who heads ICMR’s state registry in Delhi, said lung cancer cases have been increasing 2 to 3 per cent each year.
“Lung cancer in India so far has only been associated with smoking, so usually that is what we blame for the staggering numbers. But inhalation of diesel fumes from vehicles and diesel generator sets causes cancer by breaking the DNA of various cells in the body,” Dr Jhulka said.
According to AIIMS data, out of around 13,000 new cancer cases each year, almost one-third are in non-smokers. “The problem with diesel is nobody is immune from its exposure; when you are on the road, exposure is inevitable. It can affect anybody,” said Dr Shubendu Mudgal, occupational and environmental health specialist.
Particulate from diesel, primarily less than 2.5 microns in diameter, enters the lungs and penetrates the lower respiratory tract and blood vessels around the heart. “The exhaust exacerbates existing allergies and conditions like asthma, irritating the nose and lung tissue and making attacks more severe,” said Dr S K Chhabra, professor of respiratory medicine at Vallabhbhai Patel Chest Institute. “It also causes sudden conditions like cough, irritation in the eyes, nausea and difficulty in breathing.”
Since the particles are finer, they penetrate deeper and have been linked to cardiovascular events, said Dr Randeep Guleria, head of respiratory medicine at AIIMS.
Nitrogen dioxide from the exhaust can damage lung tissues irreversibly, lower one’s immunity and cause brain damage.
In 2012, WHO moved diesel up from its position for 25 years in the risk category of “probable carcinogen” (Group 2A) to “known carcinogen” (Group 1) for lung cancers. The France-based International Agency for Research on Cancer under WHO based this decision on two epidemiological studies published by the National Cancer Institute in the US.
Dr Christopher Portier, chairman of the IARC working group, said in a statement in June 2012, “The scientific evidence was compelling and the working group’s conclusion was unanimous: diesel engine exhaust causes lung cancer in humans.”
Scientists who were part of the international deliberation, speaking to The Indian Express in a telephonic interview just after the notification, had said the risk upgrade was due to the lack of “stringent regulations”in developing countries, such as India.
“Measures (in the US and Europe) like reducing the sulphur content in fuel, changing engine design to burn diesel fuel more efficiently and reductions in emissions through exhaust control technology have helped,” Dr Robert Baan, senior peer scientist at IARC, told The Indian Express then. “But in countries like India, it will take decades for such measures to come into place, so we needed to issue a warning.”
WHO experts were convinced there was at least a 30-40 per cent higher chance of lung cancer with inhalation of diesel fumes than what was believed. “Also, where we believed heavily exposed occupational groups like mine workers and truck drivers were at risk earlier, now we have extended it to the general population —basically anybody who is within breathing range of the fumes,” Dr Baan said.
International research, most recently at Zuyd University in the Netherlands, has shown that inhalation of diesel fumes causes stress responses in the brain, which in turn causes cellular damage in the long term. Such oxidative stress in the long term has been associated with diseases such as Alzheimer’s and Parkinson’s.
Several studies have also indicated adverse effects on foetal development when pregnant women are exposed to diesel fumes. Scientists from the Danish National Research Centre for the Working Environment have shown in trials with mice that inhalation of the fumes can damage foetal DNA.
A 2013 study by the International Council on Clean Transportation, titled “Impact of standards on premature mortality and emissions: India in global context”, found approximately 10 per cent of all years of life lost from exposure to vehicle emissions around the world occur in India. Without new limits on vehicle emissions and fuel sulphur content, the number of early deaths caused by emission of fine particles in urban areas will nearly quadruple by 2030. But if new emission limits are set on vehicles in India, it could cut the number of early deaths by 84 per cent in 2030, adding 6.2 million years cumulatively through 2030.
Ray Minjares, ICCT, describes how policies against diesel emissions can help. “(Government policies in the US) have led in the city of Los Angeles, for example, to a 50% reduction in lung cancer risk due to diesel engine controls alone,” he said.
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