Physical agent

1b Physical Agents. Physical agents include mechanical trauma, extremes of temperature and radiation, electric shock, and so on, which may damage tissues directly or indirectly via ischemia or secondary inflammation. 

In recent years there has been an increasing recognition of the harm that physical agents can do to the health of people at work. Injuries from this 

1 Mild Occasional blanching attacks affecting tips of one or more fingers 

3 Severe Frequent attacks affecting all phalanges of most fingers 

4 Very severe As in 3 with trophic skin changes (tips) 

Growing tissues are most sensitive to ionizing radiation. DNA synthesis is inhibited, yet the action of x-rays is indirect. They produce free radicals, which in turn react with DNA and thus produce point mutations or chromosomal breaks. 

Large doses of ultraviolet light can damage DNA. In humans this damage is confined to the skin, since, unlike x-rays, ultraviolet light is easily absorbed. The chemical lesion in this case is the formation of dimers between adjacent thymine residues on the same DNA strand. Unless corrected or removed, these dimers will stop DNA synthesis. 

DNA repair Because most mutations are very damaging, even the simplest organisms have enzyme systems that repair DNA. These DNA repair systems are important because genetic defects in them can cause some human diseases. 

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Threshold Eimit Values for Chemical Substances and Physical Agents, 1992—1993, The American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio. 

Evaluations of occupational exposure to physical agents such as noise, radiation or heat, biological agents, and multiple chemical agents are similar to the process for single chemical substances but have some key differences. 

TENfor Chemical Substances and Physical Agents in the Workroom Environment, with Intended Changesfor 1980, ACGIH, Cincinnati, Ohio, 1985, Table Z.l. 

Antimicrobial agents refers to all chemical and physical agents used to combat microorganisms. 

Sterilant is a chemical or physical agent that destroys all forms of microbial life. 

ECOTOxicoLOGY The study of toxic effects of chemical and physical agents on living organisms as well as human beings, especially on populations and communities within defined ecosystems. 

MUTAGEN A chemical or physical agent that can cause a change (mutation) in the genetic material of a living cell. 

TERATOGEN A chcmical or physical agent that can cause defects in a developing embryo or foetus when the pregnant female is exposed to the harmful agent. 

On and off the job, everyone is exposed to a great variety of chemical and physical agents, most of which do no harm under ordinary circumstances, but all of which have the potential for being injurious at some level and under some conditions of exposure. How a material is used is the major determinant of the hazard potential. 

In exposures by inhalation of airborne materials, the dose is the concentration multiplied by the time (CT), and is roughly a constant for any given material and specified effect. The CT value can be used to provide a rough approximation of other combinations of concentration and time which would have about the same effect. Although this concept must be used very cautiously and cannot be applied at extreme conditions of either concentration or time, it is most important in setting limits for airborne contaminants and physical agents in respect to environmental exposures. The worker is exposed for various periods of time, day after day, to the... 

The TLVs, as recommended and published by the ACGIH, refer to concentrations of airborne contaminants or levels of physical agents, and represent the conditions to which it is believed nearly all workers may be repeatedly exposed day after day without adverse effects. TLVs are based on the results of animal experiments, limited human experiments, some industrial experience and, when possible, a combination of all three. 

After you record the steps of the job, review each step to determine the hazards that exist or that might occur. There are several ways to identify job hazards evaluate the ways human error might contribute to a hazard, record the types of potential incidents and the physical agents involved, and make sure that procedures are clearly written. 

American Conference of Governmental Industrial Hygienists. Threshold limit values for chemical substances and physical agents and biological exposure indices. ACGIH, Cincinnati, OH. 1999. 

Exposure limits Guidelines for worker exposure to physical agents and hazardous chemicals, usually expressed as an allowable time of exposure or an air concentration below which health hazards are unlikely to occur among most exposed workers. 

Since 1970 tlie field of healtli risk assessment Itas received widespread attention witliin both tlie scientific and regulatoiy committees. It has also attracted tlie attention of the public. Properly conducted risk assessments have received fairly broad acceptance, in part because they put into perspective the terms to. ic, Itazard, and risk. Toxicity is an inlierent property of all substances. It states tliat all chemical and physical agents can produce adverse healtli effects at some dose or under specific exposure conditions. In contrast, exposure to a chemical tliat lias tlie capacity to produce a particular type of adverse effect, represents a health hazard. Risk, however, is tlie probability or likelihood tliat an adverse outcome will occur in a person or a group tliat is exposed to a particular concentration or dose of the hazardous agent. Tlierefore, risk can be generally a function of exposure and dose. Consequently, healtli risk assessment is defined as tlie process or procedure used to estimate tlie likelihood that... 

The term risk assessment is not only used to describe the likelihood of an ad crse response to a chemical or physical agent, but it has also been used to describe the likelihood of any unwanted event. This subject is treated in more detail in tlie next Part. These include risks such as explosions or injuries in tlie workplace natural catastrophes injury or deatli due to various voluntary activities such as skiing, sky diving, flying, and bimgee Jumping diseases deatli due to natural causes and many others. ... 

Health risk assessment is defined as Uie process or procedure used to estimate Uie likelihood that humans or ecological systems will be adversely affected by a chemical or physical agent under a specific set of conditions. 

Exposure is defined as llie contact of an organism (hmnans in llie case of health risk assessment) with a chemical or physical agent (3). 

Physical agents include zinc oxide and titanium dioxide. These are the most effective sunscreens because they reflect UVA and UVB. When applied to the skin, they induce a white or ashen color, which many patients find cosmetically unacceptable. New micronized formulations of these agents are available which enhance cosmetic acceptability. Sunscreens... 

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