Exposure to pollutants causing serious health hazards

Lahore: Air pollution’s damaging impact on human health is well established. Exposure to pollutants is causing serious health hazards such as skin, lungs and heart diseases, especially during the winter season.

Besides putting humans at risk of getting diseases, the pollutants are also damaging the yield and nutritional value of food crops. As such, the high-level of air pollution is a serious threat to food security. Similarly, smog is dangerous not only for humans but also for plants and food crops.

Smog is made up of many chemicals, including nitrogen oxides (NOx), sulphur dioxide (SOx), carbon monoxide (CO), volatile organic compounds (VOCs), particulate matter (PM) and ground-level ozone (O3).

Muhammad Asim, CropLife Biotechnology and Seed Committee Lead said that yes, air pollution is a serious threat.

“Usually, we are concerned about pollution due to harmful effects on human health. But it is equally or even more harmful for the plants and food crops, which are all the time under the open sky.”

Though many studies have identified the harmful impact of pollution on food crops, he suggested carrying out a Pakistan specific study and taking measures accordingly to ensure food security.

The increasing productivity depends on using quality inputs such as seeds, fertilisers and pesticides and timely watering of food crops.

A Stanford University-led study reveals how nitrogen oxides found in car exhaust and industrial emissions affect crop productivity.

As per a study of the University of California, pollution from soot and ozone has caused a major decrease in crop yields in India, despite improvements in agricultural technology.

The study showed that the overall air pollution has caused a third of loss in wheat yield and one-fifth of loss in the rice yield. This new study suggests that air pollution from ozone and soot caused far more loss of crop yield than climate change.

An increase in the temperature and a change in precipitation, as a result of anthropogenic climate change, has caused a 3.5 per cent decrease in wheat yield on a country level. However, air pollution has caused more than 32 per cent decrease in wheat yield during the same period.

Soot or black carbon is emitted mainly from burning plants and fossil fuels. It directly absorbs sunlight, reducing the amount of light for photosynthesis.

Ozone is formed due to chemical reactions of precursors, including NOx and VOCs in the presence of the sunlight. NOx are mainly generated from fossil fuel combustion, while VOCs are emitted from both natural resources and human activities.

Ozone enters leaves during normal gas exchange. As a strong oxidant, ozone causes symptoms such as yellowing, cell injury, tiny light-tan irregular spots, bronzing and reddening. This directly affects the growth of crops and reduces their yield.

Wheat is very sensitive to ozone exposure. This pollutant has an even bigger impact on the yields of soyabean, peanuts and cotton.

Since the emission of soot and ozone precursors is significantly larger in China, the impact on Chinese agriculture is expected to be even larger.

A research by the UK’s Centre for Ecology and Hydrology estimates that O3 reduces the yield of wheat, rice, maize and soyabean by up to 227 million tonnes/annum globally, including in North and South America, India, China, the US, Bangladesh and Indonesia.

The highest production losses caused by O3 for soyabean are in North and South America, for wheat, in India and China, for rice, in parts of India, Bangladesh, China and Indonesia and for maize, in China and the US.

The most affected areas are also often at risk of high losses from pests, diseases and heat stress.

Ozone concentrations are increasing in the developing regions such as East Asia and Southeast Asia and are predicted to continue to increase over the coming decades. As such, ozone is a global problem requiring investments from the industry and the governments from around the world. However, this is a long-term goal, which will take time for its achievement.

The researchers are also looking at short-term solutions, including breeding new varieties of crops that are more resilient to ozone; better timing of irrigation and the development of non-toxic agrichemicals. They say most crop breeding programmes have been targeted at increasing or maintaining the yield rather than increasing stability of yield under stress.

“Yes, the use of quality inputs, modern equipment and best farming practices are necessary to increase crop yields. This is the way forward to achieve the much-needed food security and improve the livelihood of rural communities. But excessive air pollution due to a number of factors has emerged as a big issue.

According to Asim, “There is a need to take short- and long-term measures to save crops from the hazards of particulate matter and toxic pollutants in the atmosphere.”

He suggested carrying out a comprehensive study to identify the intensity of threats and taking measures accordingly to save food crops.

“One can clearly see deposition of particulate matter on leaves close to pathways. Such depositions and invisible pollutants hinder the photosynthesis process, affecting the crops health. The scenario not only reduces the crop yields but also affects their nutritional value and quality. This is not a good omen for the food security”, Asim said, adding that the importance of exposure of crops to sunlight for a longer duration could be gauged by the difference of maize yields during the two different seasons. “A major factor behind 30 per cent more yield of maize crop sown in January-February is prolonged exposure to sunlight,” he said.

Asim suggested taking all possible measures to control the atmospheric pollution and to save the health of humans and food crops.

“The government should stick to the plan of closure of brick kilns at peak winter season, besides taking measures to reduce emissions from stationary and moving sources. The farmers are resorting to burning of crop residue as a cost effective solution. This practice is not only damaging the environment but also destroying friendly microbes. The government should enable the farmers to use modern machinery to remove crop leftovers, which will help save the environment and beneficial microbes,” he remarked.

Aamer Hayat Bhandara, a progressive farmer from Pakpattan and co-founder of Agriculture Republic and Digital Dera, said that there is a need to take atmospheric pollution seriously.

“The first step is to recognise the fact that air pollution affects crop yields, nutritional value and quality. Pollutants negatively affect photosynthetic CO2 fixation and energy metabolism, produce reactive oxygen species (ROS), which adversely affect biochemical processes of plants and reduce their tolerance capacity to other stresses also.”

“Not only concentration but also the combination of pollutants and duration of exposure affect crop health. There is a need for a global action, as the scenario poses a threat to world food security,” he said, while accepting the contribution of the agriculture sector in the atmospheric pollution through crop residue burning.

Sectoral emission inventory of Punjab shows that the major portion of total air pollutant emissions come from transport, which holds 43 per cent share; followed by 25 per cent from industries, 20 per cent from agriculture and 12 per cent from others.

“Yes, the agriculture sector is contributing to atmospheric pollution. But its share is far less than transport and industry sectors. Besides, agriculture is worst affected by the air pollution. There is a need to reduce emissions from major sectors. For minimising emissions from the agriculture sector, the government should help the farmers adopt modern technology for the disposal of crop residue,” he added.