doi:10.1038/nindia.2013.137 Published online 19 October 2013
Across South Asia, a disturbing and hitherto unaccounted amount of smoke is making its way stealthily into the air — the kind of smoke people chose to revere, inhale and quietly ignore. This is the smoke from tonnes of incense sticks in temples, mosques and graveyards as also from burning the dead in open funeral pyres. The smoke has been adding significantly to the region's 'brown carbon' and 'volatile organic compound' emissions but remains completely missing from national health indices or international climate models.
Scientists from Pandit Ravishankar Shukla University (PRSU) in Raipur, Chattisgarh along with colleagues from the Desert Research Institute (DRI) in Reno, Nevada, USA have now accounted for the first time how much these religious practices are actually contributing to national emissions in the region 1, 2.
It turns out that the funeral pyres alone could be contributing as much as 92 Gg/year (Giga grams per year) of light-absorbing carbon aerosols. This, they say, is equivalent to almost 23 percent of the total carbonaceous aerosol mass produced by human-burnt fossil fuels, and 10 percent of biofuels in the South Asian region.
Additionally, samples collected from marriage ceremonies, Muslim graveyards, Hindu and Buddhist temples in Chattisgarh state of India indicate emissions of massive quantities of carcinogenic volatile organic compounds (VOC). Extrapolated to a national scale, the figures turn out to be 0.001 Terra grams per year (Tg/yr), which the scientists term as 'very huge'. (Total VOC emission estimate from all ritual activities was found to be 7.388 Tg/year out of which crematoria alone contributed 7.387 Tg/year).
Says Rajan Chakrabarty from DRI," Our main motivation to investigate funeral pyres and widely-prevalent cultural practices in India stemmed from the lack of data about these emission sources in current regional emission inventories used by global climate models. Current inventories include pollutants primarily from technology-based (or energy production) sources such as fossil fuel and residential biofuel burning."
Hence, when Shamsh Pervez from the PRSU in Chattisgarh visited DRI as a Fulbright fellow in 2011, they laid out the blueprint for the study. Their investigations began when Pervez returned to India.
An interesting thing the team found in funeral pyres were the organic carbon particles (and not black carbon) as primary emitters. These absorb sunlight and caused heating. "Conventional organic carbon aerosols are treated in climate models as non-absorbing in the visible spectrum. This class of light-absorbing organic carbon is known as brown carbon aerosols", Chakrabarty says.
Their study on funeral pyre emissions in India and Nepal pointed out that over South Asia, one could expect not just black carbon (or soot) but brown carbon also playing a major warming effect and subsequently impacting the climate.
"We need to study this better to understand the effects of brown carbon and climate impacts over South Asia from previously non-inventoried and unstudied sources," he points out.
Carbon aerosols are known to be the second largest anthropogenic contributor to global warming after carbon dioxide. The dark particles settling on snow make snow covers absorb more sunlight and accelerate glacial melting. Chakrabarty's earlier work in the north-east Indian city of Guwahati revealed that alarmingly high pollution levels in the Brahmaputra river might be resulting in an outflow of pollutants into the Himalayas, melting glaciers faster and interfering with India's monsoon cycle3.
Between 2011 and 2012, Pervez and his colleagues hopped from marriage ceremonies to graveyards and temples to shrines in Raipur city measuring what they call the 'emission factors' of plumes from embers and flames. Alongside the regular incense, they found people burning barks of mango and sal (Shorea rodusta) trees, cow dung, cow urine, dry leaves, oil, vermillion powder, camphor, ghee (clarified butter), cotton and grains in these rituals. The scientists then measured fourteen deadly volatile organic compounds from these samples including formaldehyde, benzene, styrene and 1, 3 butadiene.
"There are three million religious places of worship in India alone and over 10 million marriages take place every year in this country according to the 2011 census. When these results were multiplied to fit these scales, the quantum of emissions was just baffling," Pervez told Nature India.
The scientists feel they have to tread cautiously in suggesting mitigation measures for religious practices-induced warming and health hazards since these are deeply-entrenched and culturally sensitive issues. "No wonder the cases of chronic bronchitis and lung cancer are much higher among people conducting these religious practices but that, of course, is a matter of another scientific study," Pervez says.
He says it is possible, however, to inculcate climate and health-friendly practices among people without hurting their religious sentiments. "For example, this month during the religious Hindu festival of Sharad Purnima, which involves cooking kheer (a sweetmeat) in the open and keeping it in the open overnight in the belief that it turns into nectar in the auspicious full moon light, we advocated that people cover it with transparent sheets. It would mean that moonlight does reach the kheer and at the same time it remains untouched by the heavy load of pollutants in the Chattisgarh air."
The advocacy bore fruit and people have taken to the practice well, Pervez says. Similarly, for religious burning practices he suggests making a start by shunning all synthetic burning materials and sticking to safer biomaterials such as wood. As of now, using the most recent Hindu and Sikh population death-rate data, they estimate that more than four tera grams of burning material is used annually in India and Nepal, with the highest amount being used in the Indo-Gangetic plains and western Indian states.