 |
 |
 |
 |
      |
|
How
should I decontaminate during response actions?
This page provides information
on decontaminating buildings or specific areas,
systems, or items within buildings after an actual
release of anthrax. Anthrax decontamination is
a repetitive process that may involve the use of
multiple decontamination processes and technologies.
Selection of appropriate technologies varies depending
on factors specific to the release and to the technologies
themselves, but the primary considerations are
always the effectiveness and safety of the products
and processes.
|
|
 |
| Planning
for Decontamination |
Cleaning an area or item
contaminated by anthrax involves numerous and
variable issues that are specific to individual
locations. No single technology, process, or
strategy will be effective in every case. Responders
must develop a decontamination plan that takes
into account the following:
- The nature of the contamination: including
the type of anthrax involved, how it entered
the facility, and the physical characteristics
that affect the spread of contamination.
- The extent of contamination: including
the amount of contamination and possible pathways
by which it could have or will spread.
- The objectives of decontamination: including
the intended re-use of the facility and building
systems and whether items will be decontaminated
for re-use or treated for disposal.
The extent of contamination
and how the contamination spread are critical considerations
in isolating affected areas and selecting appropriate
decontamination technologies. For example, if spores
are widely dispersed and have traveled through
the air, decontamination may involve extensive
isolation and fumigation. In contrast, if
the contamination is limited to a small area and
spores are not likely to become airborne, then
minimal isolation and surface decontamination methods
alone may suffice.
All stakeholders--local
authorities, building owners and residents, federal,
state, and local environmental and health agencies,
the affected public, and others--should be consulted
before decontamination begins. A site health and
safety plan (HASP) is needed to protect workers
inside and outside the contaminated area, as well
as the surrounding population. The facility manager
should notify employees and others (such as union
representatives) of the nature and scope of the
work and its expected duration.
More detailed information
about HASPs can be found on the HASP page
of this eTool.
|
| Preparing
for Decontamination |
The results of the sampling
for extent of contamination should make it possible
to distinguish between contaminated and uncontaminated
areas and to determine the types of surfaces
involved. To prevent the spread of contamination
by movement of workers or equipment, it may be
advisable to isolate the contaminated area, depending
on the impacted area and the extent of contamination.
Decontamination should address the following:
- Hidden sources of
contamination: Desktop computers
and other objects with internal fans
that draw air into the case may have
filters or electrostatic devices to
control dust intake. These filters
or the equipment chassis may be a reservoir
of contamination. If selected technologies
may damage the item or may not penetrate
to hidden locations, then these items
may be dealt with in an alternative
manner. The manufacturer of the device
should be consulted if it is to be
saved for re-use.
|
|
 |
- Pre-cleaning: Excessive
amounts of dirt or other organic material on
the surface to be cleaned may decrease the
effectiveness of the selected decontamination
method. Using certain techniques, such as HEPA
vacuuming, to remove some of the dirt and
debris could reduce the need to perform more
aggressive chemical decontamination.
- Removal of items: To
reduce potential spread of contamination, items
should be decontaminated in place. If the selected
technology will destroy an item that must be
salvaged, then the item may be removed and
decontaminated elsewhere with an alternative
technology. This requires a means of safe transport
and a separate isolation chamber, which adds
complexity to the decontamination process.
Additional, more detailed
information about sampling for Bacillus
anthracis, can be found on the Sampling page
of this eTool.
|
| Decontamination
Technologies |
Decontamination technologies
can be divided into three categories:
- Surface decontamination
products, which are used to treat
spores on hard, non-porous surfaces such
as desks, walls, and hard flooring. There
are two methods to treat surfaces:
- High Efficiency
Particulate Air (HEPA)
Vacuuming: accomplishes two
purposes: (1) it helps remove dirt
and other debris that may reduce
the effectiveness of subsequent decontamination,
and (2) it also removes some of the
spores, reducing the number that
must be killed by subsequent decontamination.
An advantage of this technology is
that there is little potential for
damage to furnishings. A limitation
of this technology is that it can
only remove surface contamination.
The operator must also avoid allowing
the exhaust to stir the air in the
affected room and must safely dispose
of contaminated filters.
- Liquid Antimicrobial
Products - Not for Porous Surfaces: may
be used to inactivate spores on hard
surfaces only. These products--which
can be applied by pouring, mopping,
or spraying--include oxidizing, bleaching,
or other agents such as aqueous chlorine
dioxide, sodium hypochlorite, hydrogen
peroxide, and peroxyacetic acid combined.
Several factors should be considered
when deciding which liquid antimicrobial
products to use and how to apply
them. Each product affects surfaces
differently in terms of corrosivity,
staining, and residue. These products
will be effective only if the directions
for use of the product are followed
precisely (such as mixing directions,
application method and dosage rate,
pre-cleaning of surfaces, and contact
time).
|
|
HEPA filters
can be attached to
high-volume vacuums such as this.
 |
- Fumigation, which
involves use of an antimicrobial gas or vapor
to destroy aerosolized spores and spores adhered
to non-porous and porous surfaces. In addition
to decontaminating a variety of surfaces, fumigants
are able to decontaminate airborne spores that
a surface cleaner would miss.
- Other decontamination
products, which are primarily used
in chambers or other specialized equipment.
Technologies that can be used to decontaminate
specific items outside the affected area
or environment include the following:
- Chemical Sterilization: chemicals
such as ethylene oxide, chlorine dioxide,
or paraformaldehyde are used to kill spores
on discrete items placed in a sterilization
chamber. Sufficient aeration of the items
following treatment is necessary to remove
residual amounts of the sterilant and any
toxic by-products that may have formed. For
effective decontamination, each chemical
sterilant has specified ranges of temperature,
relative humidity, concentration, and duration
of application.
- Irradiation: irradiation
techniques, including cobalt-60 and electron
beam technologies, can effectively destroy
anthrax. These techniques are generally available
only for off-site decontamination. They may
destroy magnetic media such as film or videotape,
and they tend to be expensive.
Selection of the appropriate
technology will require an evaluation of the specific
site conditions and nature of contamination. Other
considerations include the conditions required
for effective application (for example, humidity
for fumigations or pH for certain surface treatments),
how the technology will affect the area or item
being treated, and the risks associated with use
(such as physical, chemical, and toxicologic parameters
of the product).
The Environmental Protection Agency's (EPA) Technology
Innovation Office (TIO) has developed an information
clearinghouse (www.EPATechBiT.org)
as a centralized location to collect and disseminate
information about decontamination technologies
and also for technology vendors to provide information.
|
| Judging
the Effectiveness of Decontamination |
There are separate criteria,
described below, for judging the effectiveness
of decontamination of objects in an off-site
sterilization chamber, and for decontamination
of sites such as offices or buildings.
- For objects decontaminated in an off-site
sterilization chamber, biological indicators
such as surrogate spore test strips, may be
placed in the chamber along with the objects.
Although the optimal results of decontamination
would be if the biological indicators showed
no evidence of bacterial growth, OSHA believes
that there may be safe alternatives to the "no
growth" decontamination.
- To determine whether decontamination of a
site has been effective, a rigorous round of
environmental sampling should be performed
following the decontamination process, and
the samples should be cultured for Bacillus
anthracis in a nationally accredited
lab. Rigorous environmental sampling should
be done in all decontaminated sites, regardless
of type of technology used or the extent of
the decontamination. In areas that have been
fumigated, biological indicators (such as surrogate
spore strips) may be used to determine whether
the fumigant has effectively permeated the
area under specific conditions (such as concentration,
time, temperature, and relative humidity) sufficient
to kill Bacillus anthracis spores.
The results of the culture of both the environmental
samples and the biological indicators should
be evaluated to determine the effectiveness
of the fumigation. Again, the optimal results
of decontamination would be if the biological
indicators showed no evidence of bacterial
growth. However, OSHA believes that there may
be safe alternatives to the "no growth" decontamination.
A different technology may
be used for further decontaminating an area in
which sampling showed the presence of viable anthrax
spores. For example, if evidence of bacterial growth
is found only on a desk in an office that was fumigated,
an approved liquid sporicidal product may be applied
to complete decontamination of the desk.
Once an area has been determined to be effectively
decontaminated, there is no guarantee that all
viable spores have been eliminated, even when post-decontamination
samples show no growth. Moreover, statistical calculations
of the effectiveness of sampling and analytical
methods indicate that some spores may remain in
a decontaminated area even though environmental
sampling shows "no growth." Nevertheless,
the potential risk of a person contracting the
disease in such an area is considered to be extremely
low.
Although the "no growth" decontamination
goal may be the best possible way to ensure safety
in re-occupying a decontaminated area, OSHA believes
that there may be safe alternatives, especially
in workplace situations where the use of PPE, special
work practices, or other engineering controls might
also minimize the risk of disease.
This approach is consistent with the NCP, which
allows case-by-case decisions based on the future
use of the site and other controls that might be
used to ensure safety. Decisions on alternative
options such as these would have to be site-specific,
and supported by experts in epidemiology, public
health, industrial hygiene, and environmental protection.
The basis for these types of decisions should also
be thoroughly documented.
Additional information about decontamination techniques
and process, and post-decontamination sampling
strategies can be found on the Sampling page
of this eTool.
|
|
|
| |
|
| | | | |
| | |
|
 |
 |
 |
|
Back
to Top 
www.osha.gov
