Chapter 25: Indoor Air Pollution

Sources of Indoor Air Pollution

• Secondhand smoke– Most hazardous common indoor air pollutant

• Legionella pneumophila– Bacterium that causes a type of pneumonia

called Legionnaires’ disease when inhaled.

• Some molds (fungal growths) in buildings release toxic spores.– Cause chronic inflammation and scarring of

lungs

Sources of Indoor Air Pollution

• Radon gas – seeps up naturally from soils and rocks below

buildings – Thought to be the second most common cause

of lung cancer.

• Pesticides – Deliberately or inadvertently applied in

buildings to control pest– Are toxic to people as well

Sources of Indoor Air Pollution

• Some varieties of asbestos– Known to cause a particular type of lung cancer

• Formaldehyde – A VOC, used in many materials found in homes and

offices.

– Emit formaldehyde as a gas into buildings.

• Dust mites and pollen – irritate the respiratory system, nose, eyes, and skin of

people who are sensitive to them.

Dust mite

Pollen grains

Sources of Indoor Air Pollution

• Common indoor air pollutants are often highly concentrated compared with outdoor levels.

• Why?– There are so many potential indoor sources of

pollutants. (Furniture, beds, carpet, plastics)– The effectiveness of the steps we have taken to

conserve energy in buildings (ie, weather stripping) has led to the trapping of pollutants inside.

Heating, Ventilation, and Air-Conditioning Systems

• Systems are designed to provide a comfortable indoor environment for people.

• Design depends on a number of variables– Including the activity of people in the building, air

temperature and humidity, and air quality.

• Done correctly it will– Provide thermal comfort for people inhabiting the

building. – Provide the necessary ventilation (utilizing outdoor air)– Remove common air pollutants via exhaust fans and

filters

Pathways, Processes, and Driving Forces

• Many air pollutants originate within buildings and may be concentrated there because of lack of proper ventilation.

• Other air pollutants may enter by infiltration,– Through cracks and other openings in the

foundations and walls (Radon, VOC’s)– Or by way of ventilation systems. (proximity to

roads)

Pathways, Processes, and Driving Forces

• A chimney effect (or stack effect) – Occurs when there is a temperature differential

between the indoor and outdoor environments.– Warmer air rises in the building to the upper

levels, it is replaced in the lower portion of the building by outdoor air.

– Secondhand smoke, may also be drawn into a building by the chimney effect.

Building Occupants

• People living or working in particular indoor environments react to pollutants in different ways:– Some groups of people are particularly

susceptible to indoor air pollution problems.– The symptoms reported by people in a

particular environment vary.– In some cases, the symptoms reported result

from factors other than air pollution.

Particularly Susceptible People

• A person’s susceptibility to a particular air pollutant also depends on genetic factors, lifestyle, and age.– Sometimes a matter of concentration rather than

susceptibility.– Older people and children are generally more sensitive.– People suffering from chronic lung or respiratory

diseases are more susceptible.– Individuals who have suppressed immune systems.– Some people, when exposed to chemicals, develop

multiple chemical sensitivity (MCS).

Symptoms of Indoor Air Pollution

• A great variety of symptoms can result from exposure to indoor air pollutants. – Nosebleeds, chronic sinus infections, headaches, and

irritation of the skin or eyes, nose, and throat. – More serious problems include loss of balance and

memory, chronic fatigue, difficulty in speaking, and allergic reactions, including asthma.

– Other pollutants cause dizziness or nausea. – Radon, asbestos, and chemicals such as benzene, may

have long-term chronic health effects (cancer).

Sick Buildings

• There are two types of sick buildings:– Buildings w/ identifiable problems

• Occurrences of toxic molds or bacteria known to cause disease.

• Diseases are known as building-related illnesses (BRI).

– Buildings w/ sick building syndrome (SBS)• Symptoms people report cannot be traced to any one

known cause.

Sick Buildings

• When the cause is not detected. A number of things may be happening:– The complaints result from the combined effects of a

number of contaminants present in the building.

– Environmental stress from another source is responsible.

– Employment-related stress may be leading to the symptoms reported.

– Pollutants or toxins may be present but not identified.

Environmental Tobacco Smoke

• Environmental tobacco smoke (ETS)– Secondhand smoke– Comes from two sources:

• smoke exhaled by smokers

• smoke emitted from burning tobacco in cigarettes, cigars, or pipes.

– People who are exposed to ETS are referred to as passive smokers.

Environmental Tobacco Smoke

• It is hazardous for the following reasons:– Tobacco smoke contains several thousand chemicals,

many of which are irritants.

– Studies of nonsmoking workers exposed to ETS found that they have reduced airway functions, suffer more illnesses, and lose more work time than those not exposed to ETS.

– In the US, about 3,000 deaths from lung cancer and 40,000 deaths from heart disease a year are thought to be associated with ETS.

Radon Gas

• Radon is a naturally occurring radioactive gas that is colorless, odorless, and tasteless. – Radioactive decay chain from radiogenic

uranium to stable lead – Radon-222 has a half-life of 3.8 days, is the

product of radioactive decay of radium-226. – Radon decays with emission of an alpha

particle to polonium-218, which has a half-life of ~ 3 minutes

Geology and Radon Gas

• The concentration of radon gas that reaches the surface of the Earth and thus can enter our dwellings is – Related to the concentration of radon in the

rocks (generally granitic rock) and soil. – Some regions in the United States contain

bedrock with an above-average natural concentration of uranium.

How Does Radon Gas Enter Building?

• Radon gas enters homes and other buildings in three main ways:– 1. It migrates up from soil and rock into

basements and lower floors.– 2. Dissolved in groundwater, it is pumped into

wells and then into homes.– 3. Radon-contaminated materials, such as

building blocks that are used in construction.

Radon Resistant Techniques for Homes and Other Building

• Protection is straightforward and relatively inexpensive.

• Techniques are variable depending on the type of foundation a particular home has, – The basic strategy is to prevent radon from

entering– And to safely ensure that radon is removed

from the home site.

• A. Gas Permeable Layer: – Allow the soil gas to

move freely underneath the house.

• B. Plastic Sheeting: – Help prevent the soil

gas from entering the home.

• C. Sealing and Caulking: – Openings in the

concrete foundation floor are sealed to reduce soil gas entry into the home.

• D. Vent Pipe: – A PVC pipe runs from

the gas-permeable layer through the house to the roof to safely vent radon above the house.

• E. Junction Box: – An electrical junction

box is installed if an electric venting fan is needed.

Indoor Air Pollution and Green Buildings

• Building green.– The processes involves using building designs

that result in less pollution and better use of resources.

– Providing for a good indoor environmental quality is a significant part.

• Designing, constructing, and maintaining buildings that minimize indoor air pollutants.

• Ensuring that fresh air is supplied and circulated, and managing moisture content to remove the threat of moisture-related problems such as mold.

Control of Indoor Air Pollution

• There are strong financial incentives to provide workers w/ a clean air environment.

• A good starting point would be passing environmental legislation requiring minimum indoor air quality standards. – Including increases in the inflow of fresh air

through ventilation. This concept is at odds with the principles of Energy Efficiency….

Control of Indoor Air Pollution

• One of the principal means for controlling quality is by dilution– Fresh outdoor air mixed via a ventilating air-

conditioning system and windows that can be opened.

• Various types of air-cleaning systems reduce potential pollutants– Such as particles, vapors, and gases.

– Can be installed as part of the heating, ventilation, and AC system or as stand-alone appliances.

Control of Indoor Air Pollution

• Education also plays an important role – May involve deciding not to install unvented or poorly

vented appliances.

– Educated people are more aware of their legal rights with respect to product liability and safety.

– Education provides people with the information necessary to make decisions concerning exposure and strategies to avoid potentially hazardous conditions in the home and workplace.