Chapter 1 - The Air We Breathe

Expression of concentration Algebraic handling makes it possible to make inter-conversion between % and ppm concentrations. For example:

▪ 1 % = 1/100 = 1x10000/1000000 = 10000/1000000 = 10000 ppm ▪ 0.1 % = 0.1/100 = 0.1x10000/1000000 = 1000/1000000 = 1000 ppm ▪ 0.01 % = 0.01/100 = 0.01x10000/1000000 = 100/1000000 = 100 ppm ***************************** ▪ so how do we convert 1% to ppm - 1% means parts per hundred - now we are going to multiply top & bottom by 10,000 so we can make 100 become 1,000,000 - so now we have 10,000 on the top and 1,000,000 on the bottom ▪ to convert 1ppm to a percent, you would instead divide the top and bottom by 10,000

Aerosols (3) Catalytic Converter (5)

▪ Aerosols consist of particles, both liquid and solid, that remain suspended in the air rather than settling out. - Smoke is a familiar aerosol. ▪ SO2 emissions in the US are declining thanks to the stringent regulations by the Clean Air Act. ▪ Catalytic converters are the devices installed in the exhaust systems of automobiles to reduce emissions. ▪ Catalytic converters change CO to CO2 , NO2 to N2 and O2 , reducing the emissions of CO and NO2 to the air. ▪ Fast acceleration and high speed driving lead to incomplete combustion of gasoline (hydrocarbons) ▪ this results in the increased emissions of CO and unburned hydrocarbons which are referred to as VOCs, or volatile organic compounds. ▪ Catalytic converters lower the VOCs emissions by burning them with oxygen which is in exhaust stream unused in the engine cylinders.

Exhaled Air (4)

▪ Again nitrogen is the most abundant but here it is instead taking up about 76% ▪ Second most abundant is again oxygen at 16% ▪ Argon remains the same at 0.9% - CO2 increases all the way to 4% and water up to 4% as well

CO (4)

▪ CO has a nickname as "the silent killer." - people don't always recognize when they are breathing in carbon monoxide ▪ It is odorless and can be detected around auto exhaust or furnace emissions in a confined space. ▪ Once in the lungs, it enters the bloodstream and disrupts the delivery of oxygen throughout the body. ************************************* ▪ of those 6 major air pollutants, here we see two major air pollutants, carbon monoxide & ozone ▪ CO is called the "silent killer" because it doesn't have smell - people quite often get intoxicated when they are sitting inside an automobile with car engine running and the windows closed - the carbon monoxide gas can creep in and people get killed - OR if the furnaces in the basement in the house can release carbon monoxide ▪ if the house does not have good ventilation system then carbon monoxide can creep in and people can get intoxicated , sometimes leading to death

Two criteria to determine the indoor air quality level (2)

(1) Loci of pollutant generation: outdoor versus indoor (2) Reactivity of pollutant

The fate of NO (9)

(1) NO + O2 → NO2 ▪ This is not a favorable path, because it requires high concentration of NO to proceed quickly. - The concentration of NO even in polluted air is not high enough to follow this path. (2) VOC + •OH → A A + O2 → A' A' + NO → A" + NO2 ▪ Through these complex paths NO converts to NO2 and this is a favorable route. ▪ In short, if the air contains sufficient concentrations of NO, O2, VOCs, and •OH, you have the right ingredients to form NO2. ▪ NO2 is toxic and a player in the formation of ozone in the troposphere and one of the major contributors to acid rain as discussed in chapter 6.

The composition of dry air (6)

*Nitrogen and oxygen combined take up 99 % of dry air. - Other gases take up the remaining 1% of which argon takes the most.

What is air?

It's a mixture - a physical combination of two or more substances present in variable amounts.

PM (7)

▪ CO, NO2, O3, and SO2 are gases. PM and Pb are minuscule suspended particles. ▪ PM includes dust, soot, dirt and even microscopic droplets of liquid, bacteria, or viruses. ▪ PM10 has an average diameter of 10 μm or less, which is on the order of 0.0004 inches. ▪ PM2.5 has an average diameter less than 2.5 μm and thus is also called fine particles. ▪ These six pollutants are labeled by EPA as criteria air pollutants, or simply, criteria pollutants. ▪ EPA data on air quality show that there have been the dramatic decreases in criteria pollutants since the 1980s. ▪ EPA stands for environmental protection agency.

Sources of the Major Air Pollutants (5)

▪ Carbon Monoxide comes from hydrocarbons like gasoline or natural gas - So when we burn natural gas or ignite the gasoline engine it can create CO ▪ Nitrogen Dioxide is the major pollutant that automobiles generate and it exhumes __?___ part of our automobiles ▪ Sulfur Dioxide (SO2) - prime source is from coal burning power plants - Coal contains lots of sulfur

The Bad Gases (4)

▪ Carbon monoxide ▪ Ozone ▪ Sulfur oxides and nitrogen oxides (SOx & NOx) ▪ Particulate matter, PM - We'll take a closer look at each of these each in turn...

Direct Source of Sulfur Trioxide (2)

▪ Coal + O2 --> SO2 ▪ Good News: Since 1985 we have seen a 25% reduction in SO2 emissions in the U.S.

Fate of SO2: (8)

▪ Emission of SO2 from burning coal → reaction of SO2 with O2 to form sulfur trioxide, SO3 → dissolution of SO3 in water droplets in the air to produce sulfuric acid, H2SO4. ▪ This sulfuric acid formed in the atmosphere exists in aerosol droplets, which are small enough to become trapped in the lung tissue, upon inhalation, and cause severe damage. ▪ This sulfuric acid is also one of the main contributors to acid rain as discussed in chapter 6. *Recap:* ▪Burning coal → SO2 ▪SO2 + O2 → SO3 ▪SO3 + H2O → H2SO4

EPA's Air Quality Index (6)

▪ Environmental protection agency has come up with a visual way of representing the air quality ▪ They have come up with a formula called Air Quality Index ▪ 0-50 (Green) indicates that the air quality value is good - As the AQI values become higher and higher, the color gets darker, that means air quality becomes worse and worse ▪ The highest AQI values 301-500 have a very dark maroon color which means the air quality is very hazardous ▪ We may see these colors sometimes when we are watching the weather forecast

Lead (Pb) (6)

▪ Lead (Pb) exists many chemical forms and is very toxic, causing neurological problems, especially in children. ▪ A lead-containing compound, tetraethyl lead (TEL), was added to gasoline to make it burn more smoothly and eliminate "knocking." ▪ TEL also destroys the effectiveness of catalytic converters. ▪ Leaded gasoline was completely banned in the US in 1997 but has yet to be banned globally. ▪ There has been great success in the US in curbing the emissions of SO2 and Pb but less success with nitrogen oxides because nitrogen and oxygen are anywhere in the air. - so whenever air is subjected to high temperatures (as in car engines or in coal-fired power plants) N2 and O2 combine to form NO which is very reactive, unlike N2.

Inhaled air composition? (6)

▪ Nitrogen is much less reactive than oxygen and is exhaled from our lungs unchanged. ▪ Oxygen in inhaled air is used when it reacts with foods to yield CO2 and H2O. ▪ But even exhaled air still contains 16 %, indicating only a fraction of inhaled oxygen (about 25%) is used in the breakdown of foods which is called metabolism. - This makes mouth-to-mouth resuscitation possible. ▪ Dramatic increase in the CO2 in exhaled air compared to that in the inhaled air is the result of CO2 release from metabolic reactions. ▪ Most of the water in exhaled air is simply the result of evaporation from the moist surfaces within the lungs.

The composition of our air - Inhaled vs. Exhaled (9)

▪ Nitrogen is the most abundant between both inhaled and exhaled air bc nitrogen gas is *inactive* meaning it's NOT involved in any chemical reaction in our body - Bc it's inactive this means that it's composition stays pretty much the same ▪ If you look at oxygen gas, the amount of oxygen in the air is reduced during exhaled air ▪ The reason for this is because it is consumed and there is a reaction inside our body - Oxygen is used up when we digest our food ▪ Argon stays the same because (Argon , the word itself means lazy in Greek) ... argon is again inactive - It is what they call a "Noble Gas?" ... meaning it is not involved in any chemical reaction ▪ When you look at the Carbon Dioxide, there is a 100x increase from inhaled to exhaled air - The reason for this is because when we digest all of the food we take in , it breaks down eventually to carbon dioxide and water, which is why you see a rapid increase in carbon dioxide and water in exhaled air

Water Vapor (5)

▪ Notice that carbon dioxide takes up very minor portion of the air, and yet it plays critical role in global warming. We will learn about the reason for this seemingly contradicting fact in chapter 3. ▪ The concentration of water vapor in air varies by location: close to zero in desert air or as much as 5 % in a tropical rain forest. ▪ Water has a very wide range of compositions due to these variances between locations, which is why in the table on the last slide we just put down 0.0 as the composition of water in inhaled air ▪ Water vapor is a gas that we cannot see just like we cannot see oxygen gas. ▪ Although we can see steam and clouds, these are not water vapor as such. Rather, they are condensed water vapor or tiny droplets of liquid water.

Perception of risk (6)

▪ One more important factor in dealing with risks would be people's perception of a particular risk. ▪ Table 1.2 (NAAQS, national ambient air quality standards) lists the maximum concentrations considered to be safe for the general population. ▪ For example, the maximum carbon monoxide concentration in the air in which you can be exposed safe for 8 hours is 9 ppm; for 1 hour is 35 ppm. ▪ Those values in Table 1.2 also give us a basis on which to evaluate the relative amounts that are hazardous. ▪ For example, for 8 hour exposure, ozone (0.08 ppm) is about 100 times more hazardous to breathe than carbon monoxide (9 ppm). ▪ Nonetheless, carbon monoxide is still exceedingly dangerous, because you cannot sense carbon monoxide and thus you cannot move to less polluted air whereas you can sense ozone and thus move to less polluted air.

Expression of concentration - ppm concentration

▪ ppm concentration is parts per million. For example if there are 600 females per million human beings, we say female concentration is 600 ppm. More examples: - 600 ppm means 600/1000000 which is 600 parts per million. - 60 ppm means 60/1000000 which is 60 parts per million. - 6 ppm means 6/1000000 which is 6 parts per million. ***************************** - instead of parts per hundred, PPM is Parts Per Million

Indirect sources of air pollutant (ozone, a secondary pollutant) (8)

▪ Ozone (O3) does not come out of automobile exhaust or of coal-burning power plants, i.e., ozone is not directly emitted in the atmosphere. - It is produced from chemical reactions among pollutants, VOC and NO2. ▪ Pathways leading to the formation of ozone: - sunlight - NO2 → NO + O - O + O2 → O3 ▪ Ozone formation requires O, which in turn is produced when sunlight splits NO2.This is the reason why ozone is linked to sunlight. ▪ High levels of ozone are very likely to occur on long sunny summer days, especially in an urban area where stagnant air increases the air pollutants emitting from vehicles such as NO, VOCs, and NO2. ******************************** ▪ secondary pollutants are the ones that do not have a direct source but instead are formed through indirect processes - a typical example of this is ozone ▪ the pathways that lead to the formation of ozone are above in RED - people driving cars, especially on a hot summer day releases NO2 - under the sunlight, that NO2 decomposes to NO and O - That O all by itself reacts with O2 gas in the air , and then it becomes O3, which is ozone ▪ As you can see, ozone is not DIRECTLY produced, but it is formed through stepwise procedures, which is why ozone is called a secondary pollutant

Ozone (6)

▪ Ozone has a sharp odor. ▪ It can be detected around copiers, electric motors, transformers, or welding apparatus. ▪ It is toxic and even at very low concentration it can reduce lung function in healthy people. ▪ Symptoms of ozone inhalation include chest pain, coughing, sneezing, and pulmonary congestion. --> It is a bad pollutant at the earth's surface, the troposphere. But its presence in the stratosphere plays an important role in protecting our life on earth as you will see in chapter 2: ▪ It is bad in the troposphere and good in the stratosphere. ************************************** ▪ Ozone (O3) in contrast, has a very sharp odor ▪ that odor can be detected if you are sitting around a copy machine, electric motors, etx. - this can cause pulmonary disease ▪ Ozone is bad at the earth's surface because it can cause pulmonary disease, However , higher up in the stratosphere, is actually GOOD - Ozone protects our earth from the infrared rays from the sun - low = bad, higher up = good

Expression of concentration - percent concentration

▪ Percent concentration is parts per hundred. For example if there are 60 females per hundred human beings, we say female concentration is 60 %. More examples: - 6% means 6/100 which is 6 parts per hundred. - 0.6% means 0.6/100 which is 0.6 parts per hundred. - 0.06% means 0.06/100 which is 0.06 parts per hundred. **************************** - Percent is parts per hundred

Inhaled Air (5)

▪ Remember nitrogen takes up 78% and oxygen takes up 21% (together 99%) ▪ The third most abundant gas is argon , taking up .9%... so if you add those three you already have 99.9% of the composition of the air - We're left with .1% after we take these three into account ▪ Out of that .1% Carbon Dioxide (CO2) takes up .04% ... the rest of the minor gasses take up the other .06% ▪ On this chart water is put as 0.0 , but it is not actually 0.0...

Taking & assessing risks (3) - Toxicity (3) - Exposure (2)

▪ Risk assessment is an evaluation of scientific data followed by predictions about the probabilities of an occurrence. ▪ For air pollutants, the assessment of risk involves two main factors: - toxicity and exposure. ▪ Toxicity is the intrinsic health hazard of a substance. - Toxicity is difficult to assess because it is unethical to experiment on humans with pollutants. - Even if data were available to calculate the risks from a given pollutant, we still would have to ask what level of risk was acceptable and for what groups of people. ▪ Exposure is the amount of the substance encountered. - Exposure is the easier factor to evaluate because it simply depends on the concentration of the substance in the air, the length of time a person is exposed, and the amount of air inhaled into the lungs in a given period. (continued in the next slide)

The regions of the lower atmosphere

▪ The atmosphere of the earth is classified into three regions at least - there are other regions as we go up even higher BUT up to three for the earth ▪ the lowest region, up to about 7-10 miles up is called the troposphere over which most human activities are taking places ▪ the next region up 7.8- 10 to about 31 miles up is called stratosphere ▪ the next region above the 31 mile altitude is called the mesosphere ▪ in the middle of the diagram you can see the ozone layer - that layer is important for us because it protects us from ultraviolet rays of the sun ▪ when we say ozone is a pollutant , that means the ozone in the troposphere, the lowest portion of the atmosphere - make sure you understand those two different roles that ozone plays depending on the location where you find it

Converters (3)

▪ The converters also reduce the amount of Volatile Organic Compounds (VOCs) from tailpipe exhaust. ▪ One reason for removing tetraethyl lead from gasoline is that the lead can get gunked up or poison the catalysts in the converters. ▪ The other reason was to reduce the amount of lead in the air.

The regions of the atmosphere (7)

▪ Troposphere: The region (0 - 15 km or 0 - 9 miles) right above the surface of the earth. - Most air pollution occurs here. ▪ Stratosphere: The region (15 - 30 km or 9 - 19 miles) above the troposphere. - It includes the ozone layer. ▪ Mesosphere: The region above an altitude of 50 km (30 miles) ▪ The boundaries of these regions are not sharp. The separation of these regions is based on the pattern of temperature changes. ▪ The air gets thinner with altitude. Somewhere above 100 km, the atmosphere fades into the almost perfect vacuum of outer space.

Direct sources of air pollutants (SO2, NO2, PM & VOC) (6) Primary & Secondary Pollutants (4)

▪ Two major sources: - Coal-fired electric power plants & motor vehicles ▪ The major source of SO2 emissions: - Burning coals. ▪ The major source of CO, NO2, PM and VOC emissions: - Tailpipes of motor vehicles. ******************************* ▪ sometimes we classify pollutants into two categories; primary and secondary ▪ primary pollutants are the ones that have a distinct direct source - SO2, NO2, PM & VOC ▪ VOC stands for Volatile Organic Carbon

Six major air pollutants (9)

▪ carbon monoxide (CO) ▪ nitrogen dioxide (NO2) ▪ ozone (O3) ▪ sulfur dioxide (SO2) ▪ particulate matter (PM: PM10 & PM2.5) - If the size is a bigger particulate then we call is *PM 10* - If the size is a smaller particulate (diameter of 2.5) then we call it *PM2.5* ▪ lead (Pb) - Lead is very volatile which means it is very likely to be vaporized, which is why it can exist in the air *************************************** ▪ There are 6 major air pollutants ▪ Carbon Monoxide (only ONE oxide) is toxic ▪ There are two different types of particulate matter (PM) ▪