chemical hazards in work place page 174 in web book Flashcards
dust
Dust is a term used in industry to describe air-borne solid particles that
range in size from 0.1–25 μm. Evaluating dust exposure properly requires knowledge of the chemical composition, particle size, dusts concentration in air, how it is
dispersed, and many other factors.
Except for some fibrous materials, dust particles must
usually be smaller than 5 μm in order to penetrate to the alveoli or inner recess of
the lungs.
chemical hazards intro
Chemical compounds in the form of liquids, gases, mists, dusts, fumes, and
vapours can cause problems by inhalation, absorption, or ingestion. Inhalation involves air-borne contaminants that can be inhaled directly into the lungs and can be
physically classified as gases, vapour, and particulate matter including dusts, fumes,
smokes, aerosols, and mists. Inhalation, as a route of entry, is particularly important
because of the rapidity with which a toxic material can be absorbed in the lungs, pass
into the bloodstream, and reach the brain. Inhalation is the major route of entry for
hazardous chemicals in the work environment.
what can we divide respiratoty hazrads into
oxygen deficiency, in which the oxygen concentration is below the level
considered safe for human exposure;
2) air that contains harmful or toxic contaminants.
Inhaled contaminants that adversely affect the lungs fall into three general
categories:
1) aerosols, which, when deposited in the lungs, can produce either rapid local
tissue damage, some slower tissue reactions, eventual disease, or physical
plugging: an example of an aerosol is silica dust, which causes fibrotic growth
in lungs;
2) toxic vapours and gases that produce adverse reaction in the tissue of lungs:
an example of the second type of inhaled contaminant is hydrogen fluoride,
a gas that directly affects lung tissue;
3) some toxic aerosols or gases that do not affect lung tissue locally but pass
from the lungs into the bloodstream, where they are carried to other body
organs: an example of the third type of inhaled contaminant is carbon
monoxide, a toxic gas passed into the bloodstream without harming the lung.
toxcity and hazard
The toxicity of a material is not synonymous with its hazard. Toxicity is the ca -
pacity of a material to produce injury or harm when the chemical has reached
a sufficient concentration at a certain site in the body. Hazard is the probability that
this concentration in the body will occur.
toxcity and hazard
The toxicity of a material is not synonymous with its hazard. Toxicity is the ca -
pacity of a material to produce injury or harm when the chemical has reached
a sufficient concentration at a certain site in the body. Hazard is the probability that
this concentration in the body will occur.
what are the factors that affect all of this
The effects of exposure to a substance depend on dose, rate, physical state of
the substance, temperature, site of absorption, diet, and general state of a person’s
health. In evaluating the degree of exposure, the measured concentration of the air
contaminant is compared to the limits or exposure guidelines that appear in the published standards on levels of exposure.
Threshold Limit Values (TLVs)
Threshold Limit Values (TLVs) are exposure guidelines established for air-borne
concentrations of many chemical compounds. TLVs are air-borne concentrations of
substances that are believed to represent conditions under which nearly all workers
may be repeatedly exposed, day after day, without adverse effect. TLVs are based on
available information from industrial and agriculture experience; from experimental
human and animal studies; and, when possible, from a combination of the three.
Synergistic action or potentiality
Synergistic action or potentiality may occur with some combinations of air
contaminants. Such cases at present must be determined individually. Potentiating
or synergistic agents are not necessarily harmful themselves. Potentiating effects
of exposure to such agents by routes other than that of inhalation are also possible,
e.g., imbibed alcohol and inhaled narcotic.
measures for skin contract
Another major route of entry for hazardous chemicals is through skin. The most
effective way and often the only way to prevent harm is to keep the chemical from
the skin. This can be done by using mechanical handling devices, such as tongs and
baskets, and by using impermeable protective clothing, such as aprons, face shields,
and gloves. The use of gloves requires caution. Many solvents can quickly penetrate
latex rubber or neoprene gloves and come in contact with skin
meausres for respiraroty
Respirators can be used as emergency or backup protection. Respiratory protective equipment, especially the air-purifying type, is limited by leakage around
the mask edges, surface contamination, impaired efficiency with use, and need for
adequate oxygen. Unless it is correctly used and properly cared for, a respirator may
present a greater danger to an employee than no protection at all.
