fsn 1500 week 10 indoor air quality foreword the quality of the air we breathe is both a personal...

FSN 1500 Week 10

Indoor Air Quality

Foreword

The quality of the air we breathe is both a personal health and a major economic issue

Most people don’t consider how vital the quality of their indoor air is to their health, so today we’ll focus on some important indoor air quality concerns

Indoor Air Quality

The average Westerner spends about 90% of their life indoors!

Studies have shown that indoor air may be 10 - 100 times more polluted than outdoor air!

Indoor Air Quality

Some indoor air quality concerns include: radon, the combustion pollutants and asbestos.

Indoor Air Quality (Radon)

Radon - colorless, odorless, radioactive gas formed by the radioactive transformation of uranium in soil and rock.

238U ---> 222Rn + heat + 4 4 He (alpha particles) (see next slide)

Example of Radioactive Decay

http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivedecay.htm




Radon gas has a natural tendency to seep upward through cracks in rocks and soil pore spaces; it may even rise as a dissolved gas in groundwater

Radon enters a dwelling through cracks in the foundation or concrete slab, through porous construction materials (e.g., concrete), through uncapped sumps and floor drains and through gaps between utilities and the structure’s walls and floors (see figure)

The uranium content in soils and rocks and the amount of radon released does vary


However, nearly every rock and soil type emits some level of radon so every structure contains some level of radon

The U.S. Environmental Protection Agency (EPA) and the American Lung Association contend that moderate to long-term exposure to elevated levels of indoor radon and its radioactive byproducts is the second-leading cause of lung cancer


According to the EPA and the U.S. National Cancer Institute, cigarette smoking is responsible for approximately 85% of lung cancer cases and prolonged exposure to radon and its byproducts is responsible for approximately 10% of lung cancer cases


How could radon or its byproducts induce lung cancer? The key concern is the alpha particles and their potential to mutate the DNA of the lung wall cells.

The alpha particle is not very energetic; its penetration power is not great - even a few centimeters of air dampens its energy significantly (see figure)

Penetration energies of different types of nuclear radiation


However, if the alpha particle gets released into our lung cavity, some alpha particles may have enough energy to penetrate the first few millimeters of the lung wall and cause mutations in these cells

When the radon gas enters our dwellings it mixes well with the other air gases; when you inhale you could be inhaling some radon atoms


What’s the chance of a radon atom undergoing radioactive decomposition and releasing an alpha particle while in your lungs? For the average adult only about a 1 in 15,000 chance!

Why so low a chance? We need to examine the residence time of the radon in the lungs and its half-life.


Most of any adult’s inhalation gases only reside in the lungs about 30 seconds before they’re exhaled or absorbed

Half-life: the time it takes one half of a substance’s atoms to radioactively transform

The measured half-life of radon is about 3.8 days


The 1 in 15,000 chance I mentioned earlier results from the short residence time of the radon in the lungs compared to the significantly longer radon half-life

So why the concern over radon exposure possibly inducing lung cancer?

The key: radon decomposes to two radioactive solids - polonium-218 and polonium-214


Polonium-218 and polonium-214 have a tendency to adhere to aerosols (e.g., dust and smoke particles) and be drawn into the lungs

Polonium-218 has a half-life of about 3 minutes, polonium-214 half-life is even shorter; these elements decompose by emitting an alpha particle


The lung residence time for aerosols in the average adult is 30 minutes. Comparing the residence time and polonium half-lives, is it likely that alpha particles will be released into the lung wall?

Inexpensive, fairly accurate tests have been developed to measure air radon levels but not polonium levels; we assume the higher the air radon level the higher the polonium levels


Indoor air radon levels are typically measured in units of picoCuries per liter (pCi/L); the picoCurie is a measure of radioactivity, the liter a measure of air volume

1 pCi/L corresponds to 133 radon atom disintegrations in 1 liter of air in 1 hour


The U.S. EPA and other health agencies suggest that structures with levels at 4 pCi/L or greater have remediation work conducted

The World Health Organization’s action level for remediation is 2 pCi/L

The following tables illustrate the relative death risks for nonsmokers and smokers from long-term radon exposure

Radon LevelIf 1,000 people who never

smoked were exposed to this level over a lifetime*...

The risk of cancer from radon exposure compares to**...

WHAT TO DO:

20 pCi/LAbout 36 people could get lung cancer

35 times the risk of drowning Fix your home


20 times the risk of dying in a home fire

Fix your home


4 times the risk of dying in a fall Fix your home


The risk of dying in a car crash Fix your home

2 pCi/LAbout 4 person could get lung cancer

The risk of dying from poisonConsider fixing between 2 and 4 pCi/L

1.3 pCi/LAbout 2 people could get lung cancer

(Average indoor radon level)(Reducing radon levels below 2 pCi/L is difficult.)

0.4 pCi/L (Average outdoor radon level)

Note: If you are a former smoker, your risk may be higher.* Lifetime risk of lung cancer deaths from EPA Assessment of Risks from Radon in Homes (EPA 402-R-03-003).** Comparison data calculated using the Centers for Disease Control and Prevention's 1999-2001 National Center for Injury Prevention and Control Reports.

Radon LevelIf 1,000 people who smoked were exposed to this level

over a lifetime*...

The risk of cancer from radon exposure compares to**...

WHAT TO DO:Stop smoking and...


250 times the risk of drowning Fix your home


200 times the risk of dying in a home fire

Fix your home


30 times the risk of dying in a fall Fix your home


5 times the risk of dying in a car crash

Fix your home


6 times the risk of dying from poison

Consider fixing between 2 and 4 pCi/L


(Average indoor radon level)

(Reducing radon levels below 2 pCi/L is difficult.)


(Average outdoor radon level)

Note: If you are a former smoker, your risk may be lower.* Lifetime risk of lung cancer deaths from EPA Assessment of Risks from Radon in Homes (EPA 402-R-03-003).** Comparison data calculated using the Centers for Disease Control and Prevention's 1999-2001 National Center for Injury Prevention and Control Reports.


Indoor air radon levels as high as 3500 pCi/L have been measured; the outdoor average level is 0.2 – 0.4 pCi/L

All indoor air pollution risks (not just radon) are increased when we live under “closed house” (windows and doors sealed tightly and doors infrequently opened) conditions (i.e., winter, portions of spring and fall)


The radon lung cancer risk is further enhanced if significant aerosol production occurs within the dwelling

If your structure contained elevated radon levels, how could you possibly reduce these levels?

Two broad approaches: 1) improve cross-ventilation by natural or artificial means (e.g., sub-slab suction)


2) Seal or cover the radon entryways as effectively as possible (e.g., caulking, application of gas-impermeable paints, installation of water permeable/gas impermeable sump and floor drains)

There are also preconstruction radon mitigation techniques which can be employed (see figure for summary)

A = bed of permeable gravel (preconstruction)

B = gas impermeable sheeting (preconstruction)

C = caulk cracks and utility openings (usually post construction)

D = Sub-slab ventilation pipe (usually post construction)

E = ventilation fan


A dozen or so states now require indoor air radon testing to be conducted before any commercial or residential structure is sold.

How is this issue affected by Michigan's (mid-1990s) enacted real estate transfer disclosure statement?

Be forewarned: there is still much controversy, perhaps unresolvable, concerning what radon and radon byproduct exposure levels are necessary to significantly increase lung cancer risk.


Why the controversy? The only actual human data we have is from studies of underground uranium miners, typically exposed to higher radon and radon byproduct levels for longer periods than the average adult

There is definitely a linear (positive) relationship between radon exposure and lung cancer incidence for underground uranium miners


Can the risk relationship be linearly extrapolated to lower exposure levels and times to establish the lung cancer risk for the general population? The U.S. EPA thinks this is a valid approach - it employs what is called a “linear” dose-response model (see figure)

Actual Data

Linear Model

Threshold Model

Dose(Radon/Byproduct Exposure)

Res

pons

e(L

ung

Can

cer

Inci

denc

e)


Some groups have argued that the appropriate dose-response model is the “threshold” model (see previous figure); this suggests the lung cancer risk wouldn’t increase until a certain, somewhat elevated combination of radon level and exposure time was exceeded.

Why may we never be able to answer which model is more appropriate? Why should we care?


Broadly: we will likely never have the clinical data to conclusively decide whether the linear or threshold dose-response model is more appropriate - yet we must try to make risk assessments for substance exposures!

This issue illustrates the political and economic aspects of science and how the layperson could be mislead (see figures)

Detroit News 3/19/93


In 1998 the U.S. National Cancer Institute scientists published a report that evaluated eight previous studies on over 10,000 people in five countries

Using a linear model approach, they estimated a 14% increased chance of lung cancer for a person living in a residence for 30 years that has air radon levels of 4 pCi/L


What’s the status of the indoor air radon problem in Michigan? There are definitely “geographic hot spots” where elevated levels of indoor radon have been measured

See the following figures - more detailed information is available from the state (Department of Natural Resources), federal government (EPA) and the American Lung Association

Source: U.S. EPA, 2005

> 4 pCi/LHigh Potential

ModeratePotential

2-4 pCi/L

< 2 pCi/LLow Potential

Michigan Radon Potential Map


While the U.S. EPA and U.S. Geological Survey suggest that only 6% of U.S. households host air radon levels > 4 pCi/L; note from the previous slides and your handout that some geographic regions may have a much higher percentage of households whose air radon levels exceed 4 pCi/L


• Short-term (days) and long-term (months) air radon test kits are available; make sure the kits are EPA approved

• A very good long-term (90 days to year) test kit: Accustar Alpha Track AT 100 (~$20 and available at Amazon.com)

Indoor Air Quality (Combustion Pollutants) Combustion Pollutants - air pollutants resulting

when fossil fuels or other carbon-containing fuels, or volatile organic compounds, are inadequately combusted (e.g., not enough oxygen present) or the combustion gases are insufficiently vented

Major sources: wood stoves, fireplaces, coal stoves, gas appliances (water heaters, cooking ranges, clothes dryers, kerosene heaters, camping cook stoves)

Example: 2 C(s) + O2(g) 2 CO(9) (carbon monoxide)

Indoor Air Quality (Combustion Pollutants) Carbon monoxide (CO) - short term, the most

dangerous of the combustion pollutants; about 1100 people in the U.S., on the average, die each year from accidental CO poisoning (early 1990’s Journal of the American Medical Association report)

CO bonds about 250 times more effectively than oxygen to the hemoglobin molecule in your blood; the oxygen starvation to your organs can result in death!

Indoor Air Quality (Combustion Pollutants) CO is a colorless,

odorless gas; for the average adult, exposure to 400 ppm (parts per million) concentrations of CO for two hours results in death

Be aware of low-level CO exposure symptoms: flu-like symptoms, disorientation, headaches, fatigue

Indoor Air Quality (Combustion Pollutants) Health agencies suggest each home have one

or more CO monitors; the monitors are available in two types: passive and active

Passive monitors require no power source (battery or electrical cord) and typically consist of a small, mountable disk whose surface changes color as CO gases of different concentrations pass over the disk (see figure)

Indoor Air Quality (Combustion Pollutants) Although passive monitors are cheap, they are

useless unless you are visually monitoring them Active monitors are available that use a battery,

electrical cord, or both, power source See handout (and figures), some very good

active monitors are now available for sale

Indoor Air Quality (Combustion Pollutants)

The most versatile active CO monitors have two power sources (electrical and battery backup) and provide a digital readout of CO levels (see figure)


Why would health and safety officials urge that all electrically powered CO detectors be equipped with a backup battery? (see figure)

12/18/2006


Consumer advocacy groups (e.g., Consumer Reports) periodically rates CO monitors (see figure)


Listen to the news or periodically scan the Internet - like any other product, some CO detectors have been recalled by their manufacturers for failing to accurately detect harmful levels of CO or for being too sensitive (yielding false alarms)

Recent News

Note the

recent law

Oakland Press3/20/09

Be Aware

Any enclosed space (automobiles, boats, tents, hotel rooms) could be a location for carbon monoxide poisoning

Indoor Air Quality (Combustion Pollutants) Nitrogen dioxide (NO2) and sulfur dioxide (SO2)

combustion pollutants combine with air water vapor to create respirable acidic sulfuric and nitric acid aerosols

The acidic aerosols cause upper respiratory irritation; the sulfuric acid aerosols are threatening to people with asthma, allergies or lung diseases like chronic bronchitis

Indoor Air Quality (Combustion Pollutants) Formaldehyde - pungent gas (a volatile organic

compound); found in many household products including foam insulation; resins in particleboard, fiberboard and plywood paneling; some carpeting, upholstery and drapery fabric; and some plastics

Exposure is commonly associated with eye, nose and throat irritation; coughing, skin rashes, headaches, nausea, vomiting and nosebleeds


The EPA has classified formaldehyde as a probable human carcinogen (likely lower risk)

Indoor Air Quality (Asbestos)

Asbestos - collective name for two families of minerals that are flexible, fire-resistant and durable; one group of minerals is quite fibrous and the other typically consists of small, brittle needles (see figure)


Problem: most forms of asbestos can exist as microscopic, respirable particles that can remain airborne for long periods

Inhalation of asbestos particles, especially the needlelike forms, cause lung tissue scarring and is linked to several types of cancer (lung (mesothelioma), stomach)


The asbestos fibers become airborne typically as the product containing them (e.g., pipe insulation) decomposes or is fragmented (may happen accidentally or during remodeling or demolition)

Unfortunately, health problems may not become apparent until 15-40 years after prolonged exposure


Most homes built prior to 1975 probably contain some asbestos in floor or ceiling tiles, wall and pipe insulation, wallboard and attic insulation (see figure)


Local connection? Up to 700,000 Michigan homeowners (12/6/04 Detroit Free Press, page B1) may have attic insulation which contains easily fragmented asbestos

The insulation has the product name Zonolite and contains a mineral called vermiculite which is contaminated with the more dangerous form of asbestos

This product was even produced in a Dearborn, MI processing plant from 1966-1990


The U.S. is not the only country facing this indoor air quality problem.


During the late 1970s U.S. federal and state regulations required removal of identified asbestos-bearing materials - studies found that large amounts of asbestos became airborne during removal of the materials and that these fibers remained airborne for months


Today, encapsulation of asbestos-bearing materials by sealants or enclosure construction is thought to be safer; removal still done but it increases risk of accidental exposure

Be aware; this is still a relevant issue

Related Issue

During the 1950s and 1960s millions of tons of asbestos waste were dumped into the Great Lakes - this has raised concern over whether ingestion of asbestos particles in drinking water could cause stomach cancers

Indoor Air Quality

Relatively inexpensive home test kits exist for the indoor air pollutants we discussed; contact the American Lung Association or regional U.S. EPA office for direction

Indoor air quality is both a health and a business economic issue: some buildings have been abandoned or closed for costly renovations because of associated “sick building syndrome”

Indoor Air Quality

Related note: the U.S. Centers for Disease Control and Prevention stated in 2012 that an estimated 25 million Americans have asthma

One possible contributing factor? More airtight house construction resulting in less cross-ventilation and an increased exposure to indoor air pollutants?

fsn 1500 week 10 indoor air quality foreword the quality of the air we breathe is both a personal...

Documents

slide slide

indoor air quality slide

indoor air quality radon

level of radon

groundwater radon

radon atoms

outdoor air

centimeters of air