Agriculture Reference
In-Depth Information
operators, or supervisors must weigh the various factors and attempt to
establish PPE requirements and work safety practices that are practical,
sensi ble, and functional in the agricultural workplace and still provi de the
handler a significant degree of reduction in exposure to pesticides.
As discussed in previous sections, pesticides may be encountered in the
form of solids, liquids, or gases. When engineering controls or work practices
do not prevent the contact of the pesticide with the skin, PPE may be required.
For PPE to be a barrier to a potentially harmful chemical, it must be properly
designed, selected, used, and maintained. The materials of construction of the
PPE are key determinants of its barrier effectiveness and, therefore, in its selec-
tion. PPE materials available to pesticides handlers include:
•
woven fabrics, principally cotton and cotton/polyester blends
•
nonwoven fabrics, principally of polyethylene or polypropylene
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fabrics incorporating a microporous membrane
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fabrics coated or laminated with continuous films of plastic or rubber
•
free-standing films, sheets, or shaped forms of plastic or rubber.
The effectiveness of each of these types of materials as a barrier to a pesti-
cide is dependent on a wide range of factors, including:
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chemical composition of the material
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material thickness
•
material weight per unit area
•
fabric treatments (finishes)
•
fabric air permeability or porosity
•
chemical composition of the pesticide formulation
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form of the pesticide, e.g., mist, spray, bulk liquid, dust, granules,
vapor
•
amount of the pesticide
•
duration of the contact period
•
force of contact
•
temperature
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moisture presence, e.g., humidity, rain, perspiration
The movement of pesticides through clothing fabrics may occur by one or
both of two processes: penetration and permeation.
•
Penetration encompasses movement through openings between fibers
and yarns, stitching, seams, closures, or flaws by mechanisms such
as wicking, wetting, pressure gradients, bulk flow, and so forth. For
penetration to occur there must be a hole.
•
Permeation involves absorption, diffusion, and desorption of the
chemical within a film, coating, or an individual fiber. Permeation
occurs due to a concentration gradient across a continuous (i.e.,
nonporous) layer of material. Standard and customized tests exist for
