Edouard Bastarache Inc. on sat 22 nov 03
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Preventing Microbial Contamination
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by =C9douard Bastarache and Smart.Conseil
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Following the proper hygiene is essential to protecting product quality =
and employee health from microbial contamination.
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Microorganisms exist everywhere in our environment-in the air and water, =
on surfaces and on individuals. They are invisible and relatively =
unperceived; however, they are very numerous-1 gram of earth can contain =
up to 25 billion microorganisms (four times the earth's human =
population).
Microorganisms are also present in ceramic materials. While they =
typically exist in harmless quantities, the presence of nutritive =
elements, along with the right temperature, moisture and pH of the =
material, can promote the development of harmful levels of =
microorganisms. Under favorable conditions, their population can double =
every 20 minutes, causing the potential for complete contamination in =
less than one day. Such contamination can affect product quality and, in =
some cases, workers' health.
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Microorganisms at a Glance
Microorganisms can vary in size from 1 micrometer (1 =B5 =3D 10-6 meter) =
to several hundredths of a micrometer.
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Type Size
Viruses 10 to 300 =B5=20
Bacteria 1 to 10 =B5=20
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Family of Fungi Size
Yeasts 2 to 12 =B5=20
Fungi 2 =B5 to several centimeters
Molds 2 =B5 to several centimeters
Lichens 2 =B5 to several centimeters
Algae 1 =B5 to several centimeters
Protozoa 2 to 300 =B5=20
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The Needs of Microorganisms
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Needs Bacteria =
Molds and Yeasts
Light no =
no
Medium pH alkaline =
acid
Temperature 20 to 40=B0C =
20 to 35=B0C
Nutrients nitrogen, hydrogen, =
carbon nitrogen, hydrogen, carbon=20
Presence of oxygen O2 or inorganics such as =
SOx, NOx O2=20
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Common Microbial Problems in Ceramics
A microbial invasion can generally be seen through changes in the color =
of the surface, viscosity and pH value of the material. Such visual =
changes are typically accompanied by odors and gaseous emissions, as =
well as variations in the behavior of the product. Indicators containing =
gelose can be used to determine the level and type of contamination. =
These indicators make it possible to grow microorganisms quickly (within =
48 to 96 hours) so that they can be quantified and identified according =
to appearance, bacteria, yeasts or mushrooms.=20
Two common places in which microbial problems occur in pottery =
production are in liquid glazes and porous resin molds. The majority of =
disorders seen in liquid glazes are caused by bacterial activity that =
modifies viscosity and produces odors. These disorders generally occur =
with natural products that contain organic matter (such as clays) under =
the effect of heat and mineral concentration (such as high-density =
liquid glazes). A glaze that contains glue is even more susceptible to =
microbial problems, because the organic matter in the adhesives is a =
nutrient to bacteria.=20
Two distinct effects often occur with a bacterial attack in glazes:=20
=B7 Fluidification due to the consumption of adhesive components =
used in the glaze
=B7 Flocculation or thickening due to the acid dejections of =
bacteria following the consumption of the organic elements in the glaze
In either case, an adhesive or deflocculant can be added to the glaze =
containers to correct the viscosity.
Porous resin molds for high-pressure casting are another potential =
problem area. The mold capillary network is large enough (10 to 20 =B5) =
for clay fines to penetrate into it, and bacterial activity in the mold =
layer impregnated with these fines can cause the pores to become =
clogged. Unlike the bacteria problem in glazes, this situation cannot =
easily be corrected with a chemical action. (When this clogging occurs =
on the mold's surface, the mechanical action of a high-pressure water =
spray can cure the problem). The best solution is to implement regular =
anti-bacterial and anti-fungal preventive measures, such as using a =
forced hot air dryer to completely dry the mold each time it is cleaned =
and stored.1
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Opportunistic Infections
The vast majority of microorganisms are saprophytes; that is, they do =
not cause infections in most situations. However, in some cases, =
microorganisms can cause opportunistic infections-i.e., infections in =
people whose defense mechanisms are weakened due to disease, trauma, or =
procedures or products used for diagnostic or therapeutic purposes, and =
who are therefore particularly susceptible to such infections. Following =
are a few examples:
Antibiotics. A treatment by antibiotics modifies the normal flora of the =
skin, mucous membranes and digestive tract, and can lead to colonization =
of these organs by new microorganisms. This colonization is generally =
harmless unless it is followed by superinfection (invasion by indigenous =
germs or microorganisms from the environment). Predisposing factors =
include:
=B7 Chronic infections
=B7 Debilitating diseases
=B7 Use of excessive amounts of antibiotics
=B7 Use of broad-spectrum antibiotics
Modifications of Anatomical Barriers. When a person's normal anatomical =
barriers are broken, he or she cannot fight infections. Examples include =
those suffering from extensive burns or having undergone certain =
therapeutic or diagnostic procedures.
Disturbances of Cellular or Humoral Defense Mechanisms. Neoplastic and =
immunodeficiency diseases can make a person susceptible to opportunistic =
infections. These include leukemia, myelomas, aplastic anemia, AIDS, =
gammapathies and systemic lupus erythematosus. Others in this category =
are those who require treatments by radiotherapy or intensive =
immunosuppressive therapy.
Cytotoxic Drugs. Those who must take cytotoxic drugs are susceptible to =
opportunist infections due to a severe leucopenia (lowering of white =
blood cells).
Corticosteroids. The systemic use of corticosteroids disturbs many =
aspects of host defense mechanisms. Those who suffer from Cushing's =
syndrome (increased secretion of an endogenous corticosteroid, cortisol) =
also have an increased susceptibility to infections.=20
For people who have these conditions, it can be harmful to work in an =
environment where high levels of microorganisms are present. It is =
therefore imperative that workers are made aware of the potential =
dangers and that the right preventative measures are put into place to =
avoid microbial contamination.
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The Role of Biocides
Biocides are products that can be used to prevent bacterial and fungal =
growth. They are generally used at very low doses due to their high cost =
and toxicity, and are typically introduced at the beginning of a formula =
or glaze preparation in the mixing water at a rate of 0.05 to 0.50% by =
weight.=20
Biocides that combine a bactericide-fungicide with broad-spectrum =
activity (containing sulfureous aliphatic and heterocyclic compounds of =
low toxicity) are often used in ceramic applications. However, potters =
must be careful to ensure that the right level of biocide is used. If =
too small an amount is used, the biocide will not have the required =
effect and will give a false sense of security. However, using too much =
biocide can be expensive and can enhance its toxic effects. When used in =
glazes, the pH of the biocide can also affect the rheology (thickness) =
of the glaze. Biocides should be chosen for their compatibility with the =
product, and their pH level should be taken into account.
Examples of some commonly used biocides include:
=B7 Mixture of chlorinated and non-chlorinated isothiazolon =
compounds (pH 3.5 +/-0.5)
=B7 Aqueous solution of ortho-phenylphenol potassium salts (pH =
>13)
=B7 10% solution derived from oxazin with sulfur and nitrogen =
heterocyclic compounds (pH 10-11)
=B7 Aliphatic compound with sulfur heterocyclic compounds (pH =
3-5)
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Manufacturing Hygiene
Preventing microbial contamination and opportunistic infections in a =
pottery facility is usually as simple as implementing the proper =
hygiene. As soon as a bacterial contamination is noticed, the following =
precautions should be taken:=20
Treat the water. After work containers have been cleaned, they should =
also be rinsed with water containing a biocide to destroy any residual =
microorganisms.=20
Introduce a biocide at the beginning of manufacturing. The biocide must =
be added to the product at the beginning of the aqueous phase =
preparation (product to be protected + workshop water + biocide) to =
ensure that the product is adequately protected and to prevent its =
properties (mainly viscosity) from being altered by the biocide's pH =
level.=20
Protect liquid organic additives with a biocide. Liquid additives =
containing organic matter must also be protected with a biocide to =
prevent them from acting as carriers of contamination when they are =
introduced into the process (i.e., in liquid glazes in which an aqueous =
glue such as CMC is introduced, the glue should be treated with a =
biocide when manufactured to ensure its preservation).
Thoroughly clean facilities. Use a disinfectant (such as sodium =
hypochlorite or bleach*) mixed with water to clean containers in which a =
contaminated product has been stored.=20
Other preventative steps include:
=B7 Use disinfectants during cleaning=20
=B7 Avoid complex and difficult-to-clean piping (dead lines)
=B7 Keep pipes and containers empty and dry when not in use=20
=B7 Beware of dust
By knowing what to look for and following the right preventative steps, =
potters can prevent microbial contamination problems, thereby protecting =
both their product quality and their workers' health.
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NOTE:
*While bleach is an excellent disinfectant, its high pH and =
short-duration effect make it a temporary cleaning material only. It is =
not very compatible with ceramic products as a stable protective =
biocide.=20
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Biocide Suppliers
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Following are some companies that supply biocides for use in ceramic =
products:
1) Acti-Chem Specialties, Inc., 56 Quarry Rd., Trumbull, CT 06611; =
(203) 365 6530; fax (203) 365 6537; e-mail acti@actichem.com; =
http://thor.adept.co.uk
2) Dow Chemical Co., P.O. Box 1206, Midland, MI 48642; (989) =
832-1560 or (800) 447-4369; fax (989) 832-1465; e-mail dowcig@dow.com; =
www.dow.com
3) SEPPIC Inc., 30 Two Bridges Rd., Suite 210, Fairfield, NJ =
07004-1530; (973) 882 5597; fax (973) 882 5178; e-mail =
info.seppic@airliquide.com; www.seppic.com
4) R.T. Vanderbilt, P.O. Box 5150, Norwalk, CT 06856-5150; (203) =
853-1400; fax (203) 853-1452; e-mail rjohnson@rtvanderbilt.com; =
www.rtvanderbilt.com
5) Zschimmer & Schwarz (France), 10 rue Saint-Marc, 75002 Paris, =
France; (33) 1-42-33-10-33; (33) 1-40-26-23-81; e-mail =
zsf.cuir@wanadoo.fr; www.zschimmer-schwarz.com
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Reference:
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Shulman, Stanford T.; Phair, John P.; Peterson, Lance; and Warren, John =
II, The Biological and Clinical Basis of Infectious Diseases, 5th ed., =
WB Saunders Co., 1996.=20
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
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