Environmental Chemistry

Chapter 4:The Environmental and Health

Consequences of Polluted Air – Outdoors and Indoors

Copyright © 2012 by DBS

Haze

• Particles with diameter ~ visible light (0.4-0.8 μm) scatter light

Acid Rain

• Natural rain water has dissolved CO2 which forms carbonic acid (weak acid)

CO2 + H2O ⇌ H2CO3 Ka = 10-1.5

H2CO3 ⇌ H+ + HCO3- Ka = 10-6.4

• Natural rain water pH of 5.6. Rain water with pH < 5 is acid rain

• Two predominant acids responsible for the acid rain are H2SO4 and HNO3

• This pollution is not limited by state or country boundaries!

Effects of Acid Rain

• Acidification of surface water (lakes, rivers, etc), and subsequent damage to aquatic ecosystems.

– kills aquatic plants, fish and microorganisms in lakes and streams by releasing ions of Al, Pb, Hg and Cd from soils and sediments.

• Damage to forests and vegetation

– Weakens or kills trees, especially conifers at high elevations;

– Makes trees more susceptible to diseases, insects, drought, and fungi and mosses that thrive under acidic conditions;

– Stunts growth of crops such as tomatoes, soybeans, spinach, carrots, broccoli and cotton

June 23 1980

Damage to Buildings and Statues

CaCO3(s) + H+ → Ca2+ + HCO3- (aq)

HCO3-(aq) + H+

(aq) → H2CO3 (aq) → CO2 (g) + H2O(aq)

1944 2004

The Ecological Effects of Acid Rain

Major problems in Europe and East Coast.

Ohio Valley pollution is responsible or the acid rain in Ontario

Global Pattern of acidity pattern

Neutralization of Soil by Acid Rain

In North America most ofthe acidity comes fromthe burning of high sulfurcontent coal in powerplants

The effect of acid rain onbiological life dependsupon the composition ofsoil and bedrock in theArea – Acid Neutralizing Capacity (ANC)

Regions of North America with low soil alkalinity

Neutralization of Acid Rain by soil

Acidity from the rain deteriorates soil by removing plant nutrients:

K+, Ca2+, Mg2+ attached to –ve sites on clay and organic matter

H+ trades places and is retained

‘Base cations’ K+, Ca2+, Mg2+ leached into subsoil or washed away

CaCO3(s) + H+ → Ca2+ + HCO3-(aq)

HCO3-(aq) + H+(aq) → H2CO3(aq) → CO2(g) + H2O(aq)

Neutralization of Acid Rain by soil

Wet sulfate deposition

Although SO2 emissions have decreased over the years, rain acidity remains high(lack of fly ash emission which used to neutralize acidity)

Thousands of lakes have become strongly acidified

The acid rain problem of Northeast now extends to southeast

Neutralization of Acid Rain by soilHubbard Brook

New Hampshire experimental station

Half of Ca2+ and Mg2+ leached by 1996, vegetative growth almost stopped

Release of Aluminum into Soil and Water Bodies by Acid Rain

Acidified lakes also possess elevated concentrationsof Al3+ ions - leached from rocks and soil (exchanged with H+)Decreases fish populations

Havas and Jaworski, 1986

Human Health Effects

Air Pollution

• Historic air pollution problem was high levels of smoke and SO2 arising from the combustion of sulfur-containing fossil fuels

• Major threat now posed by automobiles, principally CO, NOx, VOCs and particulates (PM10)

– Photochemical reactions of NO2 and VOCs from vehicles leads to the formation of O3, a secondary long range pollutant

– Acid rain is another long-range pollutant influenced by vehicle NOx emissions

SO2

CONOxPbHC’s/VOC’sPM

O3

SmogAcid RainToxic Organics

CO2???

Health Effects of Outdoor Pollutants

Read p116-120

Carbon monoxide: binds to hemoglobin in red blood cells & reduces ability of blood to carry oxygen

Sulfur dioxide: causes constriction of airways & can cause bronchitis

Nitrogen oxides: irritate lungs, cause conditions similar to bronchitis & emphysema

Ozone: causes coughing, chest pain, shortness of breath, & eye, nose & throat irriation

Volatile organics: cause mutations, reproductive problems, & cancer

AQI

Source: http://airnow.gov

• The Air Quality Index is a scale used to report actual levels of O3 and other common pollutants

• The higher the AQI value, the greater the health concern

• As shown in the table, the AQI scale is divided into categories that correspond to different levels of health concern

Action days are usually called when the AQI gets into the unhealthy ranges. Different air pollution control agencies call them at different levels. In some places, action days are called when the AQI is forecast to be Unhealthy for Sensitive Groups, or Code Orange

Health Effects of Outdoor Pollutants

• Inferred from epidemiology• Main target organ – lungs

…The Bad

• Damages forests and crops; destroys nylon, rubber, and other materials; and injures or destroys living tissue

• A threat to people who exercise outdoors or with respiratory problems

• High concentrations of O3 cause plants to close their stomata ( cells on the underside of the plant that allow CO2 and H2O to diffuse into the tissue. This slows down photosynthesis and plant growth. O3 may also enter the plants through the stomata and directly damage internal cells

Rubber, textile dyes, fibers, and certain paints may be weakened or damaged by exposure to ozone.Some elastic materials can become brittle and crack, while paints and fabric dyes may fade more quickly

Source: http://www.ucar.edu

Health Effects

Ozone can irritate your respiratory system

Ozone can reduce lung function and make it more difficult for you to breathe as deeply and vigorously as you normally would

Ozone can aggravate asthma. When ozone levels are high, more people with asthma have attacks that require a doctor's attention or the use of additional medication. Also, asthmatics are more severely affected by the reduced lung function and irritation that ozone causes in the respiratory system

Ozone can inflame and damage cells that line your lungs. Within a few days, the damaged cells are replaced and the old cells are shed-much in the way your skin peels after a sunburn

Ozone may aggravate chronic lung diseases such as emphysema and bronchitis and reduce the immune system's ability to fight off bacterial infections in the respiratory system

Ozone may cause permanent lung damage. Repeated shortterm ozone damage to children's developing lungs may lead to reduced lung function in adulthood

Ozone can inflame the lung's lining

Healthy Lung

Lung Lining Inflamed by O3

Source: http://airnow.gov

Health Effects of Particulates

• Increase the risk of cardiovascular diseases and mortality

– Ultrafine may be especially dangerous(current drive to reduce PM2.5 may be dangerous)

– Particles penetrate the lungs, blocking and irritating air passages

– Toxic substances present in the particles

Indoor Air Pollution

Indoor air quality is important since people spend more times indoors than outdoors

Source: burn coal & wood; carpet, tobacco smoke

Formaldehyde: H2C=O,– Stable intermediate of oxidation product of methane– Can reach up to 1000 ppb (1 ppm) ……as compared to 10 ppb outdoors

Nitrogen Dioxide: NO2

– Homes that burn of natural gas (stove, heater, furnace) or kerosene have higher level of NO2

Carbon Monoxide: CO– Colorless, odorless gas whose concentration indoors increases from

incomplete burning of carbon based fuels.Tobacco Smoke– Refers to a family of six naturally occurring silicate minerals that are

fibrous. ……causes lung cancerRead more about indoor pollutants in the textbook p127-135)

Absorbed: dissolvesAdsorbed: stick to the surface

QuestionCarbon monoxide binds to hemoglobin 320 times more effectively than oxygen does. Continuous exposure of more than 50 ppm CO is accompanied by some observable impairment, 250 ppm results in loss of consciousness and 750 ppm can result in death. A room having the dimension 4 m x 3 m x 8 m is kept at 20°C by a natural gas (CH4) space heater.

Write the two balanced chemical equations for the combustion of CH4 to produce (1) CO2 and water and (2) CO and water

The fuel-air mixture of the heater is running slightly rich (CH4:O2 ratio of 1.00:1.92) resulting in some incomplete combustion to CO2. Calculate what percent of the total carbon oxides produced is carbon monoxide

CH4 + 2O2 → CO2 + 2H2O (1)CH4 + 3/2 O2 → CO + 2H2O (2)

CH4:O2 is 1:1.92A combination of the two reactions above (Eq. (1) and (2)) occurs. Let x represent thecontribution of Equation (2) and 1-x the contribution of Equation (1)

1.92 = 2(1-x) + 1.5(x)x = 0.16

16% of the total carbon oxide gases are CO.

QuestionThe heater combusts 10.0 g of methane per hour. Assuming all the carbon monoxide from the heater is expelled into the room and there is no ventilation, how long will it take before there is a danger of losing consciousness?

At 1 atm. ppm (CO) = 2.50 x 10-5 atm x 106 ppm = 25 ppm / hr

1 atm

Time to reach 250 ppm = 250 ppm =10 hr

25 ppm/hr

In 10 hrs there is a danger of an occupant losing consciousness

Moles (CH4) = mass(CH4) = 10.0 g = 0.623 mol

M(CH4) 16.042 g/mol

Moles (CO) = (0.623 mol)(0.16) = 9.97 x 10-2 mol

P(CO) = nRT/V = 9.97 x 10-2 mol x 0.0821 atm K-1 mol-1 x 293K = 2.5 x 10-5 atm

9.6 x 104 L

Relationship Between PM 2.5 and Daily Deaths in 6 Cities

Fine particles that originated from auto emissions and sulfate from burning of coal are responsible for increased mortality rate

Cities with high PM2.5 (~20 mg m-3) had 1.4% higher death rate than cities with 10 mg m-3

A 10 mg m-3 drop results in 36000 fewer earlier deaths per year

The shaded area represents uncertainty in data points

NO THRESHOLD!!!

Schwartz et al., 2002

US Death Map

Mega Cities

Source: UNEP/WHO, 1992

Laws

• In 1955, after many state and local governments had passed legislation dealing with air pollution, the federal government decided that this problem needed to be dealt with on a national level. This was the year Congress passed the Air Pollution Control Act of 1955, the nation's first piece of federal legislation on this issue. The language of the bill identified air pollution as a national problem and announced that research and additional steps to improve the situation needed to be taken. It was an act to make the nation more aware of this environmental hazard.

Eight years later, Congress passed the nation's Clean Air Act of 1963. This act dealt with reducing air pollution by setting emissions standards for stationary sources such as power plants and steel mills

Clean air act was amended in 1970 and 1990

Source: http://www.ametsoc.org/sloan/cleanair/

1970: Clean Air ActPrincipal provisions :

1. Establishing National Ambient Air Quality Standards (NAAQS). The law requires that EPA identify and set standards for pollutants identified as harmful to human health and the environmentThe six "criteria" pollutants are:

Carbon monoxideNitrogen dioxideOzoneSulfur dioxideParticulate matter with aerodynamic size less than or equal to 10 μm (PM-

10)Lead.

2. Primary and Secondary Standards. The Clean Air Act establilshes two categories of air quality standards: Primary standards set limits to protect public health. Secondary standards set limits to protect against public welfare effects, such as damage to farm crops and vegetation

3. Leaded gasoline phasedown. The law requires leaded gas to be phased out by the mid-1980s — one of the single most important and successful environmental health initiatives of the last century