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Wednesday, 02 March 2011 15:37

Exposure to Physical Agents

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Health care workers (HCWs) confront numerous physical hazards.

Electrical Hazards

Failure to meet standards for electrical equipment and its use is the most frequently cited violation in all industries. In hospitals, electrical malfunctions are the second leading cause of fires. Additionally, hospitals require that a wide variety of electrical equipment be used in hazardous environments (i.e., in wet or damp locations or adjacent to flammables or combustibles).

Recognition of these facts and the danger they may pose to patients has led most hospitals to put great effort into electrical safety promotion in patient-care areas. However, non-patient areas are sometimes neglected and employee- or hospital-owned appliances may be found with:

  • three-wire (grounded) plugs attached to two-wire (ungrounded) cords
  • ground prongs bent or cut off
  • ungrounded appliances attached to ungrounded multiple-plug “spiders”
  • extension cords with improper grounding
  • cords moulded to plugs not properly wired (25% of the x-ray equipment in one hospital study was incorrectly wired).

 

Prevention and control

It is critical that all electrical installations be in accordance with prescribed safety standards and regulations. Measures that can be taken to prevent fires and avoid shocks to employees include the following:

  • provision for regular inspection of all employee work areas by an electrical engineer to discover and correct hazardous conditions such as ungrounded or poorly maintained appliances or tools
  • inclusion of electrical safety in both orientation and in-service training programmes.

 

Employees should be instructed:

  • not to use electrical equipment with wet hands, on wet surfaces or when standing on wet floors
  • not to use devices that blow a fuse or trip a circuit breaker until they have been inspected
  • not to use any appliance, equipment or wall receptacle that appears to be damaged or in poor repair
  • to use extension cords only temporarily and only in emergency situations
  • to use extension cords designed to carry the voltage required
  • to turn off equipment before unplugging it
  • to report all shocks immediately (including small tingles) and not to use equipment again until it has been inspected.

 

Heat

Although heat-related health effects on hospital workers can include heat stroke, exhaustion, cramps and fainting, these are rare. More common are the milder effects of increased fatigue, discomfort and inability to concentrate. These are important because they may increase the risk of accidents.

Heat exposure can be measured with wet bulb and globe thermometers, expressed as the Wet Bulb Globe Temperature (WBGT) Index, which combines the effects of radiant heat and humidity with the dry bulb temperature. This testing should only be done by a skilled individual.

The boiler room, laundry and kitchen are the most common high-temperature environments in the hospital. However, in old buildings with inadequate ventilation and cooling systems heat may be a problem in many locations in summer months. Heat exposure may also be a problem where ambient temperatures are elevated and health care personnel are required to wear occlusive gowns, caps, masks and gloves.

Prevention and control

Although it may be impossible to keep some hospital settings at a comfortable temperature, there are measures to keep temperatures at acceptable levels and to ameliorate the effects of heat upon workers, including:

  • provision of adequate ventilation. Central air-conditioning systems may need to be supplemented by floor fans, for example.
  • making cool drinking water easily accessible
  • rotating employees so that periodic relief is scheduled
  • scheduling frequent breaks in cool areas.

 

Noise

Exposure to high levels of noise in the workplace is a common job hazard. The “quiet” image of hospitals notwithstanding, they can be noisy places to work.

Exposure to loud noises can cause a loss in hearing acuity. Short-term exposure to loud noises can cause a decrease in hearing called a “temporary threshold shift” (TTS). While these TTSs can be reversed with sufficient rest from high noise levels, the nerve damage resulting from long-term exposure to loud noises cannot.

The US Occupational Safety and Health Administration (OSHA) has set 90 dBA as the permissible limit per 8 hours of work. For 8-hour average exposures in excess of 85 dBA, a hearing conservation programme is mandated. (Sound level meters, the basic noise measuring instrument, are provided with three weighting networks. OSHA standards use the A scale, expressed as dBA.)

The effects of noise at the 70-dB level are reported by the National Institute of Environmental Health Sciences to be:

  • blood vessel constriction that can lead to higher blood pressure and decreased circulation in the hands and feet (perceived as coldness)
  • headaches
  • increased irritability
  • difficulty in communicating with co-workers
  • reduced ability to work
  • more difficulty with tasks that require alertness, concentration and attention to detail.

 

Food service areas, laboratories, engineering areas (which usually includes the boiler room), business office and medical records and nursing units can be so noisy that productivity is reduced. Other departments where noise levels are sometimes quite high are laundries, print shops and construction areas.

Prevention and control

If a noise survey of the facility shows that employees’ noise exposure is in excess of the OSHA standard, a noise abatement programme is required. Such a programme should include:

  • periodic measurement
  • engineering controls such as isolating noisy equipment, installing mufflers and acoustic ceilings and carpets
  • administrative controls limiting workers’ exposure time to excessive noise.

 

In addition to abatement measures, a hearing conservation programme should be established that provides for:

  • hearing tests for new employees to provide baselines for future testing
  • annual audiometric testing
  • hearing protection for use while controls are being implemented and for situations where levels cannot be brought within approved limits.

 

Inadequate Ventilation

The specific ventilation requirements for various types of equipment are engineering matters and will not be discussed here. However, both old and new facilities present general ventilation problems that warrant mentioning.

In older facilities built before central heating and cooling systems were common, ventilation problems must often be solved on a location-by-location basis. Frequently, the problem rests in achieving uniform temperatures and correct circulation.

In newer facilities that are hermetically sealed, a phenomenon called “tight-building syndrome” or “sick building syndrome” is sometimes experienced. When the circulation system does not exchange the air rapidly enough, concentrations of irritants may build up to the extent that employees may experience such reactions as sore throat, runny nose and watery eyes. This situation can provoke severe reaction in sensitized individuals. It can be exacerbated by various chemicals emitted from such sources as foam insulation, carpeting, adhesives and cleaning agents.

Prevention and control

While careful attention is paid to ventilation in sensitive areas such as surgical suites, less attention is given to general-purpose areas. It is important to alert employees to report irritant reactions that appear only in the workplace. If local air quality cannot be improved with venting, it may be necessary to transfer individuals who have become sensitized to some irritant in their workstation.

Laser Smoke

During surgical procedures using a laser or electrosurgical unit, the thermal destruction of tissue creates smoke as a by-product. NIOSH has confirmed studies showing that this smoke plume can contain toxic gases and vapours such as benzene, hydrogen cyanide and formaldehyde, bioaerosols, dead and live cellular material (including blood fragments) and viruses. At high concentrations, the smoke causes ocular and upper respiratory tract irritation in health care personnel and may create visual problems for the surgeon. The smoke has an unpleasant odour and has been shown to have mutagenic material.

Prevention and control

Exposure to airborne contaminants in such smoke can be effectively controlled by proper ventilation of the treatment room, supplemented by local exhaust ventilation (LEV) using a high-efficiency suction unit (i.e., a vacuum pump with an inlet nozzle held within 2 inches of the surgical site) that is activated throughout the procedure. Both the room ventilation system and the local exhaust ventilator should be equipped with filters and absorbers that capture particulates and absorb or inactivate airborne gases and vapours. These filters and absorbers require monitoring and replacement on a regular basis and are considered a possible biohazard requiring proper disposal.

Radiation

Ionizing radiation

When ionizing radiation strikes cells in living tissue, it may either kill the cell directly (i.e., cause burns or hair loss) or it may alter the genetic material of the cell (i.e., cause cancer or reproductive damage). Standards involving ionizing radiation may refer to exposure (the amount of radiation the body is exposed to) or dose (the amount of radiation the body absorbs) and may be expressed in terms of millirem (mrem), the usual measure of radiation, or rems (1,000 millirems).

Various jurisdictions have developed regulations governing the procurement, use, transportation and disposal of radioactive materials, as well as established limits for exposure (and in some places specific limits for dosage to various parts of the body), providing a strong measure of protection for radiation workers. In addition, institutions using radioactive materials in treatment and research generally develop their own internal controls in addition to those prescribed by law.

The greatest dangers to hospital workers are from scatter, the small amount of radiation that is deflected or reflected from the beam into the immediate vicinity, and from unexpected exposure, either because they are inadvertently exposed in an area not defined as a radiation area or because the equipment is not well maintained.

Radiation workers in diagnostic radiology (including x ray, fluoroscopy and angiography for diagnostic purposes, dental radiography and computerized axial tomography (CAT) scanners), in therapeutic radiology, in nuclear medicine for diagnostic and therapeutic procedures, and in radiopharmaceutical laboratories are carefully followed and checked for exposure, and radiation safety is usually well managed in their workstations, although there are many localities in which control is inadequate.

There are other areas not usually designated as “radiation areas”, where careful monitoring is needed to ensure that appropriate precautions are being taken by staff and that correct safeguards are provided for patients who might be exposed. These include angiography, emergency rooms, intensive care units, locations where portable x rays are being taken and operating rooms.

Prevention and control

The following protective measures are strongly recommended for ionizing radiation (x rays and radioisotopes):

  • Rooms that house radiation sources should be properly marked and entered only by authorized personnel.
  • All films should be held in place by patients or members of the patient’s family. If the patient must be held, a member of the family should do so. If staff must hold film or patients, the task should be rotated through the staff to minimize the overall dose per individual.
  • Where portable x-ray units and radioisotopes are used, only the patient and trained personnel should be allowed in the room.
  • Adequate warning should be given to nearby workers when x rays using portable units are about to be taken.
  • X-ray controls should be located to prevent the unintentional energizing of the unit.
  • X-ray room doors should be kept closed when equipment is in use.
  • All x-ray machines should be checked before each use to ensure that the secondary radiation cones and filters are in place.
  • Patients who have received radioactive implants or other therapeutic radiology procedures should be clearly identified. Bedding, dressings, wastes and so forth from such patients should be so labelled.

 

Lead aprons, gloves and goggles must be worn by employees working in the direct field or where scatter radiation levels are high. All such protective equipment should be checked annually for cracks in the lead.

Dosimeters must be worn by all personnel exposed to ionizing radiation sources. Dosimeter badges should be regularly analysed by a laboratory with good quality control, and the results should be recorded. Records must be kept not only of each employee’s personal radiation exposure but also of the receipt and disposition of all radioisotopes.

In therapeutic radiology settings, periodic dose checks should be done using lithium fluoride (LiF) solid-state dosimeters to check on system calibration. Treatment rooms should be equipped with radiation monitor-door interlock and visual-alarm systems.

During internal or intravenous treatment with radioactive sources, the patient should be housed in a room located to minimize exposure to other patients and staff and signs posted warning others not to enter. Staff contact time should be limited, and staff should be careful in handling bedding, dressings and wastes from these patients.

During fluoroscopy and angiography, the following measures can minimize unnecessary exposure:

  • full protective equipment
  • minimal number of personnel in the room
  • “dead-man” switches (must have active operator control)
  • minimal beam size and energy
  • careful shielding to reduce scatter.

 

Full protective equipment should also be used by operating-room personnel during radiation procedures, and, when possible, personnel should stand 2 m or more from the patient.

Non-ionizing radiation

Ultraviolet radiation, lasers and microwaves are non-ionizing radiation sources. They are generally far less hazardous than ionizing radiation but nevertheless require special care to prevent injury.

Ultraviolet radiation is used in germicidal lamps, in certain dermatology treatments and in air filters in some hospitals. It is also produced in welding operations. Exposure of the skin to ultraviolet light causes sunburn, ages the skin and increases the risk of skin cancer. Eye exposure can result in temporary but extremely painful conjunctivitis. Long-term exposure can lead to partial loss of vision.

Standards regarding exposure to ultraviolet radiation are not widely applicable. The best approach to prevention is education and wearing shaded protective eyeglasses.

The Bureau of Radiological Health of the US Food and Drug Administration regulates lasers and classifies them into four classes, I to IV. The laser used to position patients in radiology is considered Class I and represents minimal risk. Surgical lasers, however, can pose a significant hazard to the retina of the eye where the intense beam can cause total loss of vision. Because of the high voltage supply required, all lasers present the risk of electrical shock. The accidental reflection of the laser beam during surgical procedures can result in injury to the staff. Guidelines for laser use have been developed by the American National Standards Institute and the US Army; for example, laser users should wear protective goggles specifically designed for each type of laser and take care not to focus the beam on reflecting surfaces.

The primary concern regarding exposure to microwaves, which are used in hospitals chiefly for cooking and heating food and for diathermy treatments, is the heating effect they have on the body. The eye lens and gonads, having fewer vessels with which to remove heat, are most vulnerable to damage. The long-term effects of low-level exposure have not been established, but there is some evidence that nervous system effects, decreased sperm count, sperm malformations (at least partially reversible after exposure ceases) and cataracts may result.

Prevention and control

The OSHA standard for exposure to microwaves is 10 milliwatts per square centimetre (10 mW/cm). This is the level established to protect against the thermal effects of microwaves. In other countries where levels have been established to protect against reproductive and nervous system damage, the standards are as much as two orders of magnitude lower, that is, 0.01 mW/cm2 at 1.2 m.

To ensure the safety of workers, microwave ovens should be kept clean to protect the integrity of the door seals and should be checked for leakage at least every three months. Leakage from diathermy equipment should be monitored in the vicinity of the therapist before each treatment.

Hospital workers should be aware of the radiation hazards of ultraviolet exposure and of infrared heat used for therapy. They should have appropriate eye protection when using or repairing ultraviolet equipment, such as germicidal lamps and air purifiers or infrared instruments and equipment.

Conclusion

Physical agents represent an important class of hazards to workers in hospitals, clinics and private offices where diagnostic and therapeutic procedures are performed. These agents are discussed in more detail elsewhere in this Encyclopaedia. Their control requires education and training of all health professionals and support staff who may be involved and constant vigilance and systemic monitoring of both the equipment and the way it is used.

 

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