Smog

Course Title: Environmental Chemistry Course Code: CHEM2111 Topic: Environmental Pollution Sub Topic: Smog prepared by: Dr. Rashida Bashir Introduction: Smog is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a contraction (portmanteau) of the words smoke and fog to refer to smoky fog; its opacity, and odor. The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in London from the 19th century to the mid-20th century. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulates. Air Quality Index:  An air quality index (AQI) is used by government agencies to communicate to the public.  Public health risks increase as the air quality index rises. PM2.5 readings are often included in air quality reports from environmental authorities and companies. So it is in turn important to know about PM 2.5. Computation of Air Quality Index: Computation of the AQI requires an air pollutant concentration over a specified averaging period, obtained from an air monitor or model. Taken together, concentration and time represent the dose of the air pollutant. Health effects corresponding to a given dose are established by epidemiological research. Air pollutants vary in potency, and the function used to convert from air pollutant concentration to AQI varies by pollutant.  Its air quality index values are typically grouped into ranges. Each range is assigned a descriptor, a color code, and a standardized public health advisor.  The AQI can increase due to an increase of air emissions or from a lack of dilution of air pollutants. Stagnant air, often caused by an anticyclone, temperature inversion, or low wind speeds lets air pollution remain in a local area, leading to high concentrations of pollutants, chemical reactions between air contaminants and hazy conditions. An individual score (Individual Air Quality Index, IAQI) is assigned to each pollutant and the final AQI is the highest of these six scores. The final AQI value can be calculated either per hour or per 24 hours. The concentrations of pollutants can be measured quite differently. If the AQI value is calculated hourly, then SO2, NO2, CO concentrations are measured as average per 24h, O3 concentration is measured as average per hour and the moving average per 8h, PM2.5 and PM10 concentrations are measured as average per hour and per 24h. If the AQI value is calculated per 24h, then SO2, NO2, CO, PM2.5 and PM10 concentrations are measured as average per 24h, while O3 concentration is measured as the maximum 1h average and the maximum 24h moving average. The IAQI of each pollutant is calculated according to a formula published by the MEP Air Quality Index (AQI) Real time monitoring data and forecasts of air quality that are color-coded in terms of the air quality index are available from EPA's AirNow web site. Other organizations provide monitoring for members of sensitive groups such as asthmatics, children and adults over the age of 65. Historical air monitoring data including AQI charts and maps are available at EPA's AirData website. Detailed map about current AQI level and its two-day forecast is available from Aerostate web site. What is Particulate Matter  PM2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometers, which is about 3% the diameter of a human hair.  It is commonly written as PM2.5, particles in this category are so small that they can only be detected with an electron microscope. They are even smaller than their counterparts PM10, which are particles that are 10 micrometers or less, and are also called fine particles. What is Particulate Matter The IARC and WHO designate airborne particulates a Group 1 carcinogens. Particulates are the most harmful form of air pollution due to their ability to penetrate deep into the lungs and blood streams unfiltered, causing heart attacks, respiratory disease, and premature death. In 2013, a study involving 312,944 people in nine European countries revealed that there was no safe level of particulates and that for every increase of 10 μg/m3 in PM10, the lung cancer rate rose 22%. The smaller PM 2.5 were particularly deadly, with a 36% increase in lung cancer per 10 μg/m3 as it can penetrate deeper into the lungs. Worldwide exposure to PM2.5 contributed to 4.1 million deaths from heart disease and stroke, lung cancer, chronic lung disease, and respiratory infections in 2016. Overall, ambient particulate matter ranks as the sixth leading risk factor for premature death globally Composition: The composition of aerosols and particles depends on their source. Wind-blown mineral dust tends to be made of mineral oxides and other material blown from the Earth's crust; this particulate is light-absorbing. Sea salt is considered the secondlargest contributor in the global aerosol budget, and consists mainly of sodium chloride originated from sea spray; other constituents of atmospheric sea salt reflect the composition of sea water, and thus include magnesium, sulfate, calcium, potassium, etc. In addition, sea spray aerosols may contain organic compounds, which influence their chemistry. The mist emissions from the wet cooling towers is also source of particulate matter as they are widely used in industry and other sectors for dissipating heat in cooling systems. Organic matter can be either primary or secondary, the latter part deriving from the oxidation of volatile organic compounds (VOCs); organic material in the atmosphere may either be biogenic or anthropogenic. Organic matter influences the atmospheric radiation field by both scattering and absorption. Another important aerosol type is elemental carbon, also known as black carbon, This aerosol type includes strongly light- absorbing material and is thought to yield large positive radioactive forces. Organic matter and elemental carbon together constitute the carbonaceous fraction of aerosols. Secondary organic aerosols (SOAs), tiny "tarballs" resulting from combustion products of internal combustion engines. in the absence of ammonia, secondary compounds take an acidic form as sulfuric acid and nitric acid, all of which may contribute to the health effects of particulates. Secondary sulfate and nitrate aerosols are strong light-scatterers. This is mainly because the presence of sulfate and nitrate causes the aerosols to increase to a size that scatters light effectively. What is Smog: Smog is a kind of air pollution, originally named for the mixture of smoke and fog in the air. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulates. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke, VOC, sulfur dioxide and oxides of nitrogen. The main sources of these precursors are pollutants released into the air by gasoline and diesel-run vehicles and industrial plants. Levels of unhealthy exposure: The U.S. EPA has developed an air quality index to help explain air pollution levels to the general public. 8 hour average ozone concentrations of 85 to 104 ppb are described as "Unhealthy for Sensitive Groups", 105 ppb to 124 ppb as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy". The "very unhealthy" range for some other pollutants are: 355 μg m−3 – 424 μg m−3 for PM10; 15.5 ppm – 30.4ppm for CO and 0.65 ppm – 1.24 ppm for NO2. Types of Smog: Two types of smog are recognized: 1- Sulfurous smog 2- Photochemical smog. Sulfurous smog, which is also called “London smog,” results from a high concentration of sulfur oxides in the air and is caused by the use of sulfur-bearing fossil fuels, particularly coal combustion emissions, vehicular emissions and industrial emissions. This type of smog is aggravated by dampness concentration and of a high suspended particulate matter in the air. Nineteenth and 20th century London was well-known for this type of air pollution. The “Great Smog of 1952” was identified as the cause of over 4,000 deaths in London. Photochemical Smog: Photochemical Smog is also known as “Los Angeles smog,” Photochemical smog occurs prominently in urban areas that have large numbers of automobiles. It tends to occur more often in summer, because we have the most intense sunlight. It is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) undergo photochemical reaction in the presence of sunlight in the lower atmosphere, creating a brown haze above cities. The highly toxic ozone gas arises from the reaction of nitrogen oxides with hydrocarbon vapours in the presence of sunlight and some nitrogen dioxide is produced by the photochemical reaction of nitrogen oxide. Surface-level ozone concentrations are considered unhealthy if they exceed 70 parts per billion for eight hours or longer. The resulting smog causes a light brownish coloration of the atmosphere, visibility, plant reduced damage, irritation of the eyes, and respiratory distress. Natural Causes: An erupting volcano can emit high levels of sulphur dioxide along with a large quantity of particulates matter; two key components to the creation of smog. However, the smog created as a result of a volcanic eruption is often known as vog to distinguish it as a natural occurrence. The chemical reactions that form smog following a volcanic eruption are different than the reactions that form photochemical smog. The term smog encompasses the effect when a large amount of gas phase molecules and particulate matter are emitted to the atmosphere, creating a visible haze. The event causing a large amount of emissions can vary but still result in the formation of smog. Plants are another natural source of hydrocarbons that could undergo reactions in the atmosphere and produce smog. Globally both plants and soil contribute a substantial amount to the production of hydrocarbons, mainly by producing isoprene and terpenes. Hydrocarbons released by plants can often be more reactive than man-made hydrocarbons. For example when plants release isoprene, the isoprene reacts very quickly in the atmosphere with hydroxyl radicals. These reactions produce hydroperoxides which increase ozone formation. Biological Consequences of Smog: 1- Coughing and irritation of the eyes, chest, nose and throat: High ozone levels can irritate the respiratory system leading to coughing. These effects generally last for only a few days after exposure, but the particles in the smog can continue to damage the lungs even after the irritations disappear. 2- Aggravation of asthma: An experiment was carried out using intense air pollution similar to that of the 1952 Great Smog of London. The results from this experiment concluded that there is a link between early-life pollution exposure that leads to the development of asthma, proposing the ongoing effect of the Great Smog. Modern studies continue to find links between mortality and the presence of smog. One study, published in Nature magazine, found that smog episodes in the city of Jinan, a large city in eastern China, during 2011–15, were associated with a 5.87% (95% CI 0.16–11.58%) increase in the rate of overall mortality. This study highlights the effect of exposure to air pollution on the rate of mortality in China. Asthma conditions are worsened by smog and can trigger asthma attacks. 3- Breathing difficulties and lung damage: Bronchitis, pneumonia and emphysema are some of the lung conditions linked to the effects of smog as it damages the lining of the lungs. 4- Premature Deaths: WHO report (2013) indicated that cumulative exposure to smog heightens the chances of premature death from cancers and respiratory diseases. Thousands of premature deaths in the United States, Europe, and Asian countries are linked to inhalation of smog particles. Such chemical particles include benzene, formaldehyde, and butadiene which are all comprised of cancer-causing carcinogens. 5-Birth defects and underweight babies: Smog is highly linked to birth defects and low birth weight. Spina bifida – a condition depicting malformations of the spinal column – underdevelopment or absence of a part of the brain, are birth defects associated with smog exposure. Furthermore, studies suggest that even as low as 5 μg exposure to smog particulate matter can result in risks of underweight babies at delivery. 6-The risk of developing rickets: Heavy smog that lasts for prolonged periods blocks UV rays from reaching the earth surface. This results in low production of Vitamin D leading to rickets due to impaired metabolism of calcium and phosphorus in the bone marrow. 7-Risk of Road and Air traffic: Smog interferes with natural visibility and irritates the eyes. On this basis, it may prevent the driver or flight controller from reading important signs or signals thereby increasing the probability of road accidents or even plane crash. 8-Effect on plants: Smog inhibits the growth of plants and can lead to extensive damage to crops, trees, and vegetation. When crops and vegetables such as wheat, soybeans, tomatoes, peanuts and cotton are exposed to smog, it interferes with their ability to fight infections thus increasing susceptibility to diseases. Remarkable Solutions for Smog 1-Renewable energy sources: Renewable energy source helps in the reduction of emissions from power generating plants that heavily depend on fossil fuel. In other words, the use of renewable energy not only reduces environmental impacts but also trims down the presence of smog causing pollutants in the air. Reducing and managing vehicular and industrial emissions Vehicles and industries constitute the largest contributors of smog forming pollutants. The best way to reduce smog is to follow maintaining and managing protocol for vehicles and industrial plants and the management of gaseous emissions from cars and industries. Use of environmentally friendly consumer products The use of household products that have high levels of volatile organic compounds should be completely avoided. These products not only release hazardous materials into the atmosphere but also emit particulate matter that reacts in the presence of sunlight to form ground-level ozone. The use of environmentally friendly consumer products such as ecofriendly paints, paper, sprays, solvents and plastics therefore provides a basis for addressing smog pollution. Increasing energy efficiency and conserving energy Increasing energy efficiency and at the same time conserving energy leads to reduced gaseous emissions into the atmosphere that often result in the formation of smog. A capable and productive energy management system can go a long way in reducing smog causing pollutants in the air such as nitrogen and sulfur oxides. Smog in Pakistan The Environmental Protection Department (EPD) of Punjab has a smog policy and Punjab Clear Action Plan in place. The EPD has installed air quality monitors in major cities of Punjab, including Lahore, Gujranwala, Multan and Faisalabad. They also monitor air quality and pollution from industrial units and brick kilns. Strict action is being taken against polluters; any polluting unit is sealed and fined until the necessary apparatus which can tackle air pollution is installed. The government is also introducing zigzag technology, which is more efficient and reduces fossil fuel consumption by up to 20%. Thank you