Title: Indoor Air Pollution: Radon
1INDOOR AIR POLLUTION RADON
- In 1990 EPA placed indoor air pollution at the
top of the list of 18 sources of cancer risk - Indoor pollution is rated by risk analysis
scientists as high-risk health problem for humans - Radon is one of the three most dangerous indoor
air pollutants, along with cigarette smoke and
formaldehyde - Radon is the second leading cause of lung cancer,
after smoking - Nearly 1 in 15 homes in the U.S. has high level
of indoor radon - The U.S. Surgeon General and EPA recommend all
homes be tested for radon - Homes with high radon level can be fixed
2INDOOR AIR POLLUTION RADON
- CHARACTERISTICS
- Radioactive element
- Naturally occurring
- Colorless, odorless, and tasteless
- Derived from natural decay of uranium
- Chemically inert
- When it decays, it releases decay products
(progeny) which can attach themselves to tiny
dust particles in indoor air and can be inhaled
into human lungs, exposing them to densely
ionizing alpha particles
3INDOOR AIR POLLUTIONRADON
- Radon is estimated to cause about 20,000 deaths
per year. The number of deaths from other causes
are taken from the 1990 National Safety Council
Report.
4INDOOR AIR POLLUTIONRADON
- Most of the cancer risk resulting from radon in
the household water supply is due to inhalation
of the radioactive by-products that are produced
from radon that has been released from the water
into the air, rather than from drinking water.
5INDOOR AIR POLLUTION RADON
6INDOOR AIR POLLUTION RADON
- EPA map of radon zones, New York State.
- Zone 1, red, highest potential (greater than 4
pCi/L) - Zone 2, orange, moderate potential (from 2 to 4
pCi/L) - Zone 3, yellow, low potential (less than 2 pCi/L)
7INDOOR AIR POLLUTION RADON
- Radon levels in outdoor air, indoor air, soil
air and ground water can be very different.
8INDOOR AIR POLLUTIONRADON
- Radon Formation
- Each atom of radium decays by ejecting from its
nucleus an alpha particle composed of two
neutrons and two protons. As alpha particle is
ejected, the newly formed radon atom recoils in
the opposite direction, just as a high-powered
rifle recoils when a bullet is fired. Alpha
recoil is the most important factor affecting the
release of radon from mineral grains.
9INDOOR AIR POLLUTION RADON
- Radon can move through crack in rocks and
through pore spaces in soils. Radon moves more
rapidly through permeable soils, such as coarse
sand and gravel.
10INDOOR AIR POLLUTION RADON
- Some radon atoms remain trapped in the soil and
decay to form lead other atoms escape quickly
into the air. - Homes in areas with drier, highly permeable
soils, may have high levels of indoor radon.
11INDOOR AIR POLLUTION RADON
- Cracks in concrete slabs
- Spaces behind brick walls
- Pores and cracks in concrete blocks
- Floor wall joints
- Exposed soil as in a sump
- Weeping tile, if drained to open sump
- Mortar joints
- Loose fitting pipe penetrations
- Open tops of block walls
- Building materials such as some rocks
- Water, from some wells
12INDOOR POLLUTION RADON
- In areas where the main water supply is from
private wells and small public water works, radon
in ground water can add radon to the indoor air.
13INDOOR AIR POLLUTION RADON
- HEALTH EFFECTS
- Radon causes about 20,000 lung cancer deaths each
year (only effect definitely linked) - Even very small exposures to radon can result in
lung cancer - No threshold below which levels are harmless
- Many smokers will get lung cancer because of the
synergy between radon and cigarette smoking - Epidemiological studies (miners) an animal
studies are supporting evidence that confirm
radon as a cause of lung cancer - The BEIR (Biological Effects of Ionizing
Radiation) VI Report of the National Academy of
Sciences, the most comprehensive study to date,
supports that conclusion. -
14INDOOR AIR POLLUTION RADON
- Soil Air Radon Data
- A scientist collects samples of soil air to
determine its radon content. - The methods for measuring radon can be a passive
device buried in the soil, or a sample of soil
air collected from a probe driven into the
ground.
15INDOOR AIR POLLUTION RADON
- Methods for measuring alpha particles produced
by the decay of the radon in the air.
16INDOOR AIR POLLUTIONRADON
- Active Sub slab Suction
- It is the most common and most reliable radon
reduction method. One or more suction pipes are
inserted through the floor slab into the soil
underneath. A radon vent fan connected to the
suction pipes draws the radon gas from below the
house and releases it into the outdoor air while
creating a negative pressure (vacuum) beneath the
slab.
17INDOOR AIR POLLUTION RADON
- Radon Resistant-Construction Techniques
- Gas Permeable Layer
- Plastic Sheeting
- Sealing and Caulking
- Vent Pipe
- Junction Box
- Other radon reduction techniques include
sealing, home/room pressurization, heat recovery
ventilation and natural ventilation.
18INDOOR AIR POLLUTIONRADON
- Conclusions
- Indoor radon is a public health problem
- Millions of homes are estimated to have elevated
radon levels - The solution is straight forward
- The health risks of radon can be reduced