The International Agency for Research on Cancer (IARC) of the World Health Organization has declared that outdoor air pollution is group 1 carcinogen and that it is “carcinogenic to humans”. This is the first time that the scientists have evaluated the air people breathe for its cancer-causing potential. This is a sharp departure from assessing only specific pollutants for cancer potency.
IARC has also separately evaluated particulate matter as a component of outdoor air pollution and classified it as class 1 carcinogen. It has found clinching evidences to suggest that particulate matter increases risk of lung cancer. The tag of group 1 carcinogen is given when there is “sufficient evidence of carcinogenicity” in humans. In 2010, IARC said 223,000 lung cancer deaths occurred worldwide.
The leading scientists convened by the IARC have concluded that there is sufficient evidence that exposure to outdoor air pollution causes lung cancer and also leads to increased risk of bladder cancer. In its release, WHO-IARC has noted that this evaluation is based on the review of more than 1,000 scientific papers from studies on five continents, taking into account the carcinogenicity of various pollutants in outdoor air pollution, especially particulate matter and transport-related pollution. The findings are from large studies in Europe, North and South America and Asia. Outdoor air pollution is now in the same bracket as other deadly cancer-causing substances, including tobacco, asbestos and ultraviolet radiation.
“We have known about the respiratory outcomes of air pollution for decades, also about emerging burden of cardiovascular impacts that adds to the urgency. But now this certainty about the cancer effects puts the nail on the coffin,” says Kalpana Balakrishnan, the only Indian scientist who was part of this IARC evaluation in Leon. Balakrishnan, professor from the Department of Environmental Health Engineering at Sri Ramachandra University, Chennai, is also the director of the WHO Collaborating Center for Occupational and Environmental Health, and ICMR Center for Advanced Research on Environmental Health: Air Pollution.
This evaluation has followed a rigorous and elaborate process, looking at the extent and magnitude of population exposure to air pollution, air pollution mixture characterization, and evaluation of evidences from both epidemiological and toxicological studies. In fact, air quality data from Central Pollution Control Board and evidences from health studies carried out in Indian cities were also valuable inputs in this global evaluation. “There is no ambiguity in our conclusion anymore,” says Balakrishnan.
Ominous for India
This shocker comes at a time when in India close to half of total urban population breathes the air which exceeds the standard of PM10. One-third of urban population lives in cities with PM10 levels officially classified as critical—close to Japan’s population. At the same time, the levels of tinier PM2.5 are hitting unacceptable levels.
Cancer registry in India already shows how cancer is taking an epidemic form that demands immediate action to cut environmental risks. Indian Council of Medical Research has released in 2013 the Three Year Report of Population Based Cancer Registries, 2009 2011. This reports data collected from 25 population-based cancer registries in the country. Analysis of the data reported for selected cities shows that highest number of lung cancer occurs in Delhi, followed by Mumbai and Kolkata (see Cancer rises in the Northeast ). In Kolkata, out of the total number of cancer cases reported for 20 types of cancers in human body, the percentage share of lung cancer is highest at 12 per cent. This is a serious trend in view of the fact that air pollution, and particularly diesel pollution, is a very strong contributory factor. Given the fact that endpoint of all toxic risk is cancer, environmental risk factors should be minimized. This is particularly serious in India as the National Cancer Control Programme (NCCP) forecasts that by 2026, more than 1.4 million people will be falling in the grip of some form of cancer. NCCP has listed greater exposure to environmental carcinogens as one of the most important reasons. The mitigation strategy must reduce environmental risk from all factors. It is now beyond doubt that air pollution is an important factor.
The mounting local evidences from Indian cities paint a scary picture. Manas Ranjan Ray, a noted scientist from the National Cancer Research Institute, Kolkata, who has done extensive clinical studies across cities of India says, “We are now beginning to see more cancer incidence among the younger population.” Their studies on 10,000 adults in Delhi and Kolkata show that the tell tale signs, including chromosomal changes, functional and morphological changes in lungs are two to three times higher in these cities compared to the sample population from cleaner environment of Sundarbans in West Bengal and Himachal Pradesh.
Vinod Raina, former Head, Medical Oncology, Dr B R Ambedkar Institute-Rotary Cancer Hospital, All India Institute of Medical Sciences, Delhi, had earlier informed Down To Earth that “we’re on tip of cancer iceberg”. He said the Delhi Cancer Registry at AIIMS “reports 13,000 new cases of cancer in the capital city every year. About 10 per cent of them suffer from lung cancer. We have seen that 90 per cent of the lung cancer patients have a history of smoking. But recently, after analysing the data of 600 patients, I found that 30 per cent of them did not have any history of smoking.” The extent of lung cancer varies from place to place. The incubation period for such diseases is very long, 15 to 30 years.
Thursday’s announcement from WHO-IARC comes close on heels of the June 2012 release that had reclassified diesel emissions as a class I carcinogen for its strong link with lung cancer.Both the announcements put the spotlight on vehicular pollution that is a source of high exposure in cities. There are special concerns over vehicles as they release emissions within the breathing zone of people. As the assessment from the Health Effect Institute shows in Delhi, more than 55 per cent of its 17 million people live within the 500 metre of major roads and are directly affected by traffic emissions.
Scientists have cautioned that the latency period of cancer risk is long. It takes 15 to 20 years for this toxic effect to surface. This demands urgent and immediate policy intervention to prevent exposure early in life to reduce risk. Social and economic cost of cancer is humongous.
While India has substantially expanded air quality monitoring capacity to generate data for particulate matter, its capacity to monitor a range of air toxic is still very weak. The revised ambient air quality standards of 2009 include six air toxins and heavy metals. Air toxic reduction programme is important at a time when both industrialization and motorization is expected to spew enormous amount of air toxics. These are lethal at even very small dosage. These are strong carcinogens and need near elimination.
Currently, there are no separate mitigation strategies for air toxins in India except some efforts to control toxic components of fuels like benzene, polycyclic aromatic hydrocarbons (PAH) and aromatics. But explosive number of vehicles is negating all effects. In mega and big metro cities, including Delhi, Kolkata and Bengaluru, air quality data indicate unacceptable levels of benzene, PAH and heavy metals. Even the road dust and natural dust are no longer benign as the toxic fume from tailpipes and combustion sources settle on them and they become toxic carrier to lungs.
This is a wake up call to India. Air pollution is a ticking time bomb. The government cannot be complacent any more. Cities need action plan to meet clean air targets on an urgent scale and time. India needs leapfrog agenda to avert the public health crisis.
Air pollution and cancer
Outdoor air pollution a leading environmental cause of cancer deaths: IARC, WHO
Lung cancer incidence and long-term exposure to air pollution from traffic