A Breathing Zone Air sample is an air sample drawn from a point or
series of points within the workers immediate work area. It also provides
an acceptable estimate of a workers exposure to airborne contamination.
The last choice of engineering controls would be to use a
respirator.
The major internal pathway for radionuclides is ingestion.
A child is more radiosensitive than an adult because a child's
cells are multiplying more rapidly.
Radiation initiates destruction of human tissue through the
ionization process.
300 mg/cm2 is the thickness assumed to cover the human eye.
A negative pressure full-face respirator has a protection factor of
50. (ANSI says 50, OSHA permits up to 100, but most facilities use 50)
Exhalation is an elimination route for internal contamination.
Humidity will affect the ability of a sorbent to absorb iodine in
an air purifying respirator. So will breathing rate.
Radioactive decay is an elimination method for internal
contamination.
A face shield is not a method of controlling airborne
radioactivity.
The following are all potential sources of airborne radioactive
contamination: opening contaminated tanks, radioactive spills, and
removing/replacing HEPA filters.
To determine the airborne concentration of radioactivity to which
individuals may be exposed, we would take a breathing zone air sample.
An atmosphere that poses an immediate threat of severe exposure to
contaminants which are likely to have adverse cumulative or delayed
effects on health, is an IDLH atmosphere.
In a positive pressure air purifying respirator, contaminated air
passes through the filter by means of a blower driven by a battery.
Air sampling is a monitoring method for assessing internal
exposure.
Alpha air samples should be taken with a membrane filter.
Sloughing is not an elimination route for internal contamination.
The following are the latent effects of radiation exposure: Life
shortening, Genetic mutations, Leukemia, but Leukopemia is not.
The critical organ for I-131 is the thyroid.
Internal contamination is a problem for two reasons: It increases
the probability of damage to vital organs and it may be retained by the
body for long periods of time.
Collection of body excrements is a method of assessing internal
contamination.
In an air purifying respirator, the contaminant is captured in a
fibrous medium, usually fiberglass, sometimes cellulose, and mechanically
filtered out of breathing air.
The positive pressure air purifying respirator has specifically
designed filters called sorbents which through a process called absorption
allow the sorbent to absorb iodine.
A positive pressure air purifying respirator has a protection
factor of 1000.
A negative pressure full face respirator has a protection factor of
50.
For airborne particulate sampling, some type of physical filter
such as paper, fiberglass, or cellulose is used. Particulate filters
should not have a high saturation factor.
Airborne samples of vapors are collected on activated charcoal,
silica gel cartridges, or cryogenic traps.
Breathing zone air samples are the preferred method for sampling
the workers exposure to airborne contamination.
CAM's are susceptible to dust loading of the filter media.
Charcoal filters or silver Zellite filters are used to sample for
iodine. Silver Zellite are expensive and will absorb water or humidity.
Incorrect volumes are the most common source of air sample errors.
The Noble Gases Xenon and Krypton are breathed in and then breathed
out. (What goes in comes back out.) So they are NOT an internal hazard.
Removal of hazardous materials should be attempted prior to
considering the use of respiratory protection.
The operation of a negative pressure air purifying respirator is as
follows. During inhalation, air space inside the face plate is at a lower
pressure than outside air, as worker exhales, positive pressure in mask
opens exhalation valve.
