By Kevin Miller
The fight against disease has been in the forefront for medical
professionals, manufacturers and the general public for many years.
With every flu epidemic outbreak we clamor for methods to ensure
health and thwart intrepid germs from attacking the general population.
With the advent of hand sanitizers and anti-microbial technology we
fight bacterial and viral pathogens in the quest to disinfect our world.
But do we really know what we’re fighting and are these measures truly
making a safer environment? In recent years anti-microbial powder
coating technology emerged as one of the tactics to battle germs. Let’s
break down the elements of this technology, understand how it works
and where it can help us.
What Is Anti-Microbial
Technology?
The Environmental Protection
Agency defines anti-microbial agents
as pesticides and states: “…they are
intended to disinfect, sanitize, reduce
or mitigate the growth or development
of microbiological organisms;
or protect inanimate objects, industrial
processes or systems, surfaces,
water or other chemical substances
from contamination, fouling or deterioration
from bacteria, virus, fungi,
protozoa, slime or algae.”
Some anti-microbial agents are
considered sanitizers that are topically
applied. Hand sanitizers and
cleaning products fall under this category.
These are non-residue producing
materials and have no application
in the coatings world because their
function is temporary.
In powder coatings anti-microbial
technology provides germ killing
through the incorporation of an
anti-microbial agent. By their nature
these agents are long-lasting and persist
throughout the life of the coating.
Why Consider Anti-Microbial
Technology?
The most obvious reason to use
an anti-microbial coating is to kill
pathogens on the surfaces of products
that are deleterious to human
health. These include bacteria,
viruses and fungi. Combating the
transmission of disease can take
many forms. Foremost are personal
hygiene and sanitation measures
such as washing hands thoroughly,
properly refrigerating food products,
keeping food handling utensils and
appliances clean and the regular disinfectant
cleaning of surfaces in the
environment.
Another function of anti-microbial
technology is the protection of
inanimate objects. The proliferation
of microorganisms can have a deleterious
effect on products. Protection
of a shower curtain can be used to
illustrate this scenario. Anti-microbial
agents can be incorporated into
shower curtain materials which can
keep microorganisms from damaging
the curtain and thereby extending the
life of the shower curtain.
Other less obvious but perhaps more
business related incentives to pursue
anti-microbial strategies relate to consumer
awareness and competitive pressures.
Indeed the proliferation of disinfectant
schemes has been quite prominent in the
media.
How Are Microorganisms
Transmitted?
The most common means of spreading
germs are from respirable transmission
(coughing and sneezing) and manual contact.
Microbes are delivered to the environment
and under conducive conditions can
exponentially reproduce into large colonies
within hours.
Where Is Anti-Microbial
Technology Important?
A plethora of applications can benefit
from anti-microbial technology. The most
obvious environments and applications
include hospitals, schools, locker rooms,
public transportation, food preparation,
gymnasiums, spas and the handles/hardware
of consumer goods.
How Are Anti-Microbial
Agents Regulated?
Anti-microbial agents are considered
pesticides by the US federal government
and are therefore regulated by the Environmental
Protection Agency. They are specifically
governed by the Federal Insecticide
Fungicide and Rodenticide Act (FIFRA).
The laws and regulations can be found in
the Code of Federal Regulations 40 CFR
sections 152, 156 and 158.
The EPA recognizes two very important
classes of anti-microbial substances. One
deals with agents that are proven to kill
microbes and therefore provide a quantifiable
impact on the health of the general
public. Registration requires a high level of
testing by the EPA before being approved.
This testing can run into the hundreds of
thousands of dollars and can take years.
The second category involves EPA
recognition that the anti-microbial agent
can be used to protect the treated article
and does not necessarily improve public
health. The EPA grants the “treated articles
exemption” for a non-public-health use of a
pesticide that is intended to protect only the
treated article or substance itself. Consumers
may distinguish such products by the
absence of the EPA’s pesticide registration
number (found on the product label) of the
registered pesticide used for protecting the
article itself.
The EPA goes on further regarding
how claims can be made for products that
protect articles: “Claims for treated articles
or substances are limited to statements like,
“This product contains a preservative (e.g.,
fungicide or insecticide) built in or applied
as a coating only to protect the product. An
example of an acceptable label statement
would be:
“Antimicrobial properties are built in to inhibit
the growth of bacteria that may affect this
product. The antimicrobial properties do not
protect users or others against bacteria, viruses,
germs, or other disease organisms. Always clean
and wash this product thoroughly before and
after each use.”
Treated kitchen accessories or other food
contact articles such as a cutting board, high
chair, or conveyor belt that may come in
contact with food should carry an appropriately
qualifying statement, such as:
“This product does not protect users or others
against food-borne bacteria. Always clean and
wash this product thoroughly before and after
each use.”
Treated products such as bed pans and
potty seats that involve potential human
contact with bodily fluids or excrement
(e.g., blood, vomit, saliva, urine, or feces)
should carry an appropriate qualifying
statement, such as:
“This product does not protect users against
bacteria, viruses or other disease organisms.
Always clean and wash this product thoroughly
before and after each use.”
In addition, it should be noted that:
“The treated articles exemption is available
only for the protection of the product
and not for public health uses.”
The preservative claim and qualifying
statement on the product packaging
(type, size color) must be given no greater
prominence than other described product
features.
It is very important to note that even
though these statements are required by law
when describing a product, the use of the
terminology “Anti-Microbial” is still allowed.
In using the term “Anti-Microbial,” the
consumer of this technology, even though it
only applies to the article and not the health
of the general public, may construe the
properties beyond these statements.
How Are Surfaces Tested for
Anti-Microbial Performance?
Most anti-microbial testing follows the
JIS-Z2801 procedure developed in Japan.
Basically the surface is contaminated with
a microorganism suspended in a nutrient
broth to support reproduction. The contaminated
sample is then left to incubate in a
humid environment for 24 hours. Tests are
run in triplicate, including an uncontaminated
control specimen. Some evaluations
are run for less than 24 hours to more closely
determine kill point. At the conclusion
of the test microorganisms are counted and
compared to the original quantity.
A number of common microorganisms
are routinely tested. These include:
• Gram-negative bacteria, e.g.
Pseudomonas aeruginosa
• Gram-positive bacteria, e.g.,
Staphylococcus aureus, E. Coli, Salmonella
• Fungus, e.g., Aspergillus niger, Penicillium,
Trichophyton mentagrophytes
• Mycobacterium (cause diseases such as
tuberculosis) , e.g., M. Smegmatis, M.
Fortuitum
• Viruses, e.g., MS2 coliphage an
RNA virus, Polio virus
Antimicrobial results are expressed as
reductions in microbial populations, and are
presented in terms of Log10 reductions as
illustrated in the table below.
Common Anti-Microbial Approaches
Microbes can be eradicated through a
number of methods including the following
residue producing anti-microbial agents:
Some of these have limited use in powder coatings because they
introduce a high level of color or degrade at powder coating processing
temperatures. Most common is the use of silver and more
specifically silver coated zeolites that release silver ions in humid
conditions.
New Developments in Anti-Microbial Technology
Recently, scientists have uncovered novel technology that
provides excellent anti-microbial efficacy. This technology is just
emerging however the preliminary results are quite encouraging.
The powder coating materials utilize a novel anti-microbial agent
developed by Agienic Microbials, Inc. Their anti-microbial technology
is based on copper salts and is produced by a simple, environmentally
friendly synthetic process. It does not use precious metals
and can be delivered in a variety of forms.
Typically the efficacy of the antimicrobial agents is first established
in dilute solutions so that it is easy to compare different
materials against a variety of microbes. Agienic’s materials are
effective against a broad array of microbes. Their efficacy was first
established in solutions with copper concentration is 60 parts per
million (ppm). This data against select microbes is provided below.
Short term testing (5 minutes) was only conducted for Pseudomonas
aeruginosa and Staphylococcus aureus.
This technology offers a significant
advancement in anti-microbial performance.
As an example when nano-silver
solution was tested against Pseudomonas
aeruginosa at a 60ppm metal concentration
it showed a log kill of 1.6 at
a time point of 24 hours. Agienic has a
number of patents pending and is working
on obtaining EPA registration of
their products. Experimental products
were made to test the efficacy of these
materials in epoxy-polyester powder
coatings. The coatings showed excellent
processability and no degradation
in mechanical properties. The antimicrobial
test results on these coatings are
shown above, and as shown the coatings
were tested at 24hours (standard)
and also at shorter times (6 hrs) to see
if these were still highly antimicrobial at
shorter times.
Summary
Many schemes have been developed
to thwart the spread of germs and thereby
improve the health of the general
public and protect treated manufactured
goods. In all cases good hygiene and
housekeeping practices are strongly
encouraged. The EPA regulates these
anti-microbial agents for both the health
of the public and also to protect treated
articles. Recent scientific advances
have identified novel technology that
provides significant improvement over
prevailing technology. Further testing by
the EPA is expected to validate the performance
of these products and make
them available to the powder coating
industry.
Kevin Biller is technical editor of
Powder Coated Tough magazine.
He can be reached at 614-354-1198 or
via email at kevinbiller@yahoo.com.