Basic Calculations for Occupational Safety and Environmental Health Professionals - Mathematics and Statistics for the Environment - page 382

15.2.2 p hysiCal s tressors
Physical stressors include excessive levels of ionizing and nonionizing electromagnetic radiation,
noise, vibration, illumination, and temperature. In occupations where there is exposure to ionizing
radiation, factors such as time, distance, and shielding are important tools for ensuring worker
safety. Danger from radiation increases with the amount of time one is exposed to it; hence, the
shorter the time of exposure the smaller the radiation danger. Distance also is a valuable tool in con-
trolling exposure to both ionizing and nonionizing radiation. Radiation levels from some sources
can be estimated by comparing the squares of the distances between the work and the source. For
example, at a reference point of 10 feet from a source, the radiation is 1/100 of the intensity at 1 foot
from the source. Shielding also is a way to protect against radiation. The greater the protective mass
between a radioactive source and the worker, the lower the radiation exposure. Nonionizing radia-
tion is also dealt with by shielding workers from the source. Sometimes limiting exposure times to
nonionizing radiation or increasing the distance is not effective. Laser radiation, for example, can-
not be controlled effectively by imposing time limits. An exposure faster than the blink of an eye
can be hazardous. Increasing the distance from a laser source may require miles before the energy
level reaches a point where the exposure would not be harmful.
Noise, another significant physical hazard, can be controlled by various measures. Noise can
be reduced by installing equipment and systems that have been engineered, designed, and built to
operate quietly; by enclosing or shielding noisy equipment; by making certain that equipment is
in good repair and properly maintained with all worn or unbalanced parts replaced; by mounting
noisy equipment on special mounts to reduce vibration; and by installing silencers, mufflers, or
baffles. Substituting quiet work methods for noisy ones is another significant way to reduce noise,
for example, welding parts rather than riveting them. Also, treating floors, ceilings, and walls with
acoustical material can reduce reflected or reverberant noise. In addition, erecting sound barriers at
adjacent work stations around noisy operations will reduce worker exposure to noise generated at
adjacent work stations.
It is also possible to reduce noise exposure by increasing the distance between the source and the
receiver by isolating workers in acoustical booths, limiting workers' exposure time to noise, and by
providing hearing protection. OSHA requires that workers in noisy surroundings be periodically
tested as a precaution against hearing loss. Another physical hazard is radiant heat exposure in
factories such as steel mills. Radiant heat can be controlled by installing reflective shields and by
providing protective clothing.
15.2.3 b iologiCal s tressors
Biological stressors include bacteria, viruses, fungi, and other living organisms that can cause
acute and chronic infections by entering the body either directly or through breaks in the skin.
Occupations that deal with plants or animals or their products or with food and food processing may
expose workers to biological hazards. Laboratory and medical personnel also can be exposed to bio-
logical hazards. Any occupations that result in contact with bodily fluids pose a risk to workers from
biological hazards. In occupations where animals are involved, biological hazards are dealt with by
preventing and controlling diseases in the animal population as well as proper care and handling of
infected animals. Also, effective personal hygiene, particularly proper attention to minor cuts and
scratches, especially those on the hands and forearms, helps keep worker risks to a minimum. In
occupations where there is potential exposure to biological hazards, workers should practice proper
personal hygiene, particularly hand washing. Hospitals should provide proper ventilation, proper
personal protective equipment such as gloves and respirators, adequate infectious waste disposal
systems, and appropriate controls including isolation in instances of particularly contagious dis-
eases such as tuberculosis.