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Controlling Physical Hazards

Physical agents include heat and cold, noise, radiation, electricity and other dangers. Physical agents can occur naturally or can be produced in the workplace. For example, heat is a physical agent that is the result of the weather and is also produced by machinery.

Protecting workers from physical agents requires the same process as other hazards. First, the physical agent and its health effects must be identified. Next, working conditions must be changed to prevent exposure to the hazards. This chapter describes how to protect workers from common physical agents.

Heat

Heat can be more than uncomfortable. It can be dangerous and even deadly. Summer weather is a common cause of heat problems. Workers are also exposed to heat in boiler rooms, confined spaces and during welding or brazing. Too much heat can cause a number of health problems.

Health effects

Being exposed to heat can cause:

• Heat rash is also known as prickly heat.
  
  
• Heat cramps which are painful muscle spasms. The cramps usually are felt in the arms, legs, and stomach area. They usually occur after sweating heavily and not drinking enough liquids.
  
  
• Heat exhaustion — symptoms include tiredness, dizziness, clammy skin, heavy sweating, loss of appetite, nausea, and pain in the stomach area. These symptoms are brought on when the body loses too much fluid (dehydration) during hard physical labor.
  
  
• HEAT STROKE
  
  
  
  

  DANGER!!! HEAT STROKE CAN KILL. Heat stroke is a condition that needs immediate medical attention.

  
  
  The body can no longer cool itself. The person’s skin becomes hot and red or blotchy. Body temperature is as high as 105 degrees or more. Heat stroke can cause a person to lose consciousness and go into a coma.
  
  

Other effects of exposure include heart disease. Workers also become less alert and are more likely to injure themselves or others.

Measuring heat hazards

Knowing the temperature is only part of figuring out if it is too hot. The effects of heat increase when it is humid or when there is no breeze. A Wet Bulb Globe Temperature device gives a reading based on heat, humidity and wind speed, and provides a more accurate measure of the effects of heat on the body.

Controlling heat hazards

Engineering Controls

Ventilation and air conditioning: Air conditioning can eliminate heat hazards in buildings and vehicles. Areas with machines that cause heat need exhaust systems to remove the extra heat that is produced.

Work Practices (Administrative Controls)

The following changes can protect workers from heat:

• Scheduling: Do the hottest work during early morning, evening or night hours, or on cooler days.
  
  
• Job rotation: Divide heavy and hot work among more workers.
  
  
• Breaks: Take breaks preferably in an air-conditioned area or at least a shady place.
  
  
• Drink fluids: Replace the fluids that are lost through sweating.
  
  
• AVOID DRINKS THAT CONTAIN CAFFEINE AND ALCOHOL! Caffeine and alcohol make you lose more fluids.
  
  
• Get used to heat gradually: Workers need a chance to get used to heat (acclimatization). At first, work in hot environments should be limited to short periods. The amount of time that workers spend in the heat should be increased gradually.
  
  

Personal Protective Equipment

Light-colored clothing should be worn. Cooling vests provide some protection but can be bulky and make it harder to perform job tasks.

Cold

Health effects

• Frostbite: As the body tries to prevent heat loss, less blood reaches the surface. Hands and feet become numb and the skin freezes. Severe frostbite may require amputation of the affected parts.
  
  

  WARNING!!! Do not rub frost-bitten areas. Warm the area by soaking or running under cool or lukewarm water.

  
  
   
• Hypothermia: This is a condition that results from being in cold weather or submerged in cold water. The body can no longer create heat, causing dizziness, fatigue and can lead to unconsciousness and death.
  
  
• Trench foot: Long periods of exposure to wet and cold conditions can cause severe nerve and muscle damage in the feet.
  
  
• Eye injuries: Workers can become snowblind and the cold can cause the cornea to freeze.
  
  

Controlling cold hazards

The following steps can protect workers from the cold.

• Give workers frequent rest periods in a warm area.
  
  
• Provide clothing designed to keep cold and wind out and allow heat and perspiration to escape. The body loses heat quickly when clothes are wet. Workers should wear layers of vented clothing, insulated gloves and footwear.
  
  
• Where possible, build barriers around the worksite to block the wind.
  
  
• Supply workers with warm beverages that do not contain caffeine or
  alcohol.
  
  

Noise

Continuous or periodic noise can be harmful.

Health effects

• Temporary hearing loss: This may last for minutes, hours or days. Normal hearing does return.
  
  
• Permanent hearing loss: This usually develops gradually from being exposed to high levels of noise over a long period of time.
  
  
• Other effects: Noise can cause fatigue, nervousness and increased blood pressure, which can lead to problems such as heart disease.
  
  

Finding noise hazards

You do not need fancy equipment to know if you are exposed to noisy conditions. Your hearing may be affected if:

• is too noisy to hear your co-workers at arms-length;
  
  
• you have to turn the volume up on the TV or radio;
  
  
• you get a ringing in your ears after working in noisy areas; and/or
  
  
• family, friends and co-workers notice that you have more trouble hearing them.
  
  

Measuring Sound

The level of sound is measured in units called decibels. The abbreviation for decibels is dB. On the decibel scale, each time the number of decibels goes up by three, the level of the noise is doubled. In other words, 93 decibels is a noise that is twice as loud as a sound that is 90 decibels. Examples of common noises and their decibel levels are shown in the chart below.

Controlling noise hazards

Substitution

Use equipment that makes less noise.

Engineering Controls

Noisy machinery can be enclosed, isolated or rigged with equipment to muffle sound. Acoustical building materials and carpeting absorb sound indoors.

Work Practices (Administrative Controls)

• Rotate jobs to reduce the amount of time workers are exposed to noise.
  
  
• Move workers away from noise.
  
  
• Keep equipment lubricated and in good working order.
  
  

Personal Protective Equipment

There are different types of hearing protection that workers can wear. Ear plugs are worn in the ear and must fit the worker’s ear. They should only be worn in healthy ears. Foam plugs should be soft and springy. They must be compressed so they can expand after inserting in the ear.

The other common type of hearing protection are ear muffs that are worn outside the ear. Ear muffs require a good seal to be effective.

Laws: OSHA Standard — 29 CFR 1910.95

The OSHA noise standard limits the amount of exposure to noise to 90 decibels averaged over an 8-hour day. This means the louder the noise, the less time workers can be exposed. The chart below shows the amount of time that workers can be exposed to different decibel levels of noise.

If exposure to noise averages above 85 dB for a shift, the employer must have a hearing conservation program. This includes providing workers with hearing tests and hearing protection.

Electrical hazards

Shocks and electrocutions are all too common in sewage treatment plants. To control electrical hazards in the plant, management should take the following precautions:

• Develop and train workers in a good lockout/tagout system.
  
  
• Parts of electrical equipment that ordinarily produce arcs or sparks must be enclosed unless they are completely isolated from all combustible material.
  
  
• Switches or circuit breakers in wet locations must be enclosed in a weather-proof enclosure.
  
  
• Cabinets and cutout boxes of the surface type must be weatherproof and installed to prevent moisture from entering the cabinet. They should be mounted so there is at least a 1¼4 inch air space between them and the wall space.
  
  
• Management should install fast-acting ground-fault circuit interrupters or breakers that sense small current leaks in the circuit and cut off the electricity in a fraction of a second.
  
  
• Ground wires should be attached to the framework of the equipment and connected to a good ground (water pipe or other metal that will have direct contact with low-resistance soil). Ground wires should be checked frequently. All exposed non-current carrying parts of fixed equipment that may be energized must be grounded if located in wet or damp locations and/or when operated in excess of 150 volts. Portable ground-fault devices are available for working in the field.
  
  
• Rubber mats should be placed in front of switchboards, control panels, service panels and other equipment to prevent shock or burns.
  
  
• All hand-held electrical tools should be equipped with a “dead-man” control so that the power is automatically shut off whenever the operator releases the control.
  
  
• All hand-held portable tools operating at more than 90 volts must have a separate ground wire or be doubly insulated.
  
  
• Metal ladders should not be used in areas around electrical equipment.
  
  
• Each disconnecting means (circuit breaker, fuse boxes, etc.) must be legibly marked to indicate its purposes.
  
  
• Only qualified and trained workers should handle fallen and loose wires and connections. Trained personnel should routinely inspect all stationary and portable equipment, and circuit breakers and leaks. Personnel working in wet areas where there is a potential for shock should wear rubber or plastic protective clothing and gloves. Shoes should not have metal staples or nails.
  
  

Back injuries

Back injuries are the leading national workplace injury. Workers whose jobs require frequent lifting, loading or unloading of light or heavy weights, pushing and pulling objects, and tasks requiring bending, twisting or reaching for long periods are prime candidates for back injuries.

Too many back injury programs consist only of teaching proper lifting techniques. Proper lifting techniques include bending knees, getting a good grip on the objects, lifting with the back straight and not twisting while lifting.

Training in proper lifting techniques, however, is not enough to prevent back injuries. Back injuries are caused by too much (repetitive) lifting. Workers are frequently not in a position to bend their knees and straighten their backs. Heavy boxes often do not have handles where workers can get a good grip. The object being lifted may not be located in a clear, open space free of obstructions or slippery conditions. In addition, the worker may not be fully aware of the size and weight of an object until it is lifted. Finally, many back injuries are not a result of lifting but of pushing and pulling, twisting and turning, working for long periods with a bent back, or whole body vibration.

Too much emphasis in the past has been placed on lifting techniques and not enough on changing the workplace. A program to teach workers the proper lifting techniques should not substitute for workplace redesign to reduce the amount of lifting needed.

Preventing back injuries

The best way to prevent back injuries is to change the working conditions
(risk factors) that are causing injuries. The main risk factors are:

• strenuous efforts (such as lifting heavy objects or unbalanced loads);
  
  
• frequent lifting;
  
  
• poorly designed workplaces and equipment;
  
  
• whole body vibration; and
  
  
• extended periods of work in one position (such as stooping or sitting).
  
  

If problems exist, the following remedies should be considered:

1. Reduce the Number of Lifts Made and/or increase staffing levels to provide more lifting assistance.

2. Improve Job Design

• Build platforms or spring-loaded bins to store objects off the floor (above knee height) to eliminate the need for stooping or lifting things above shoulder height.
  
  
• Repair floors, fix wheels or otherwise engineer equipment so that pulling and pushing objects can be avoided.
  
  
• Remove obstacles to lifting or carrying (for example, high sills on the bottom of door frames, steps, tripping or slipping hazards).
  
  
• Use lifting devices, such as hooks, crowbars, rollers, jacks, trestles, conveyors, hoists, cranes and industrial trucks to reduce job strain.
  
  

3. Improve Machine Design

Replace or redesign machines which cause workers to lift while in awkward positions.

4. Establish Weight Limits

All objects which must be moved should be labeled with their weight.

• A weight limit should be established. The Canadian Union of Public Employees (CUPE) recommends 35 pounds.
  
  
• A weight limit should be placed on the amount to be lifted over a prolonged time period. CUPE recommends 528 pounds over any 15-minute period (no more than a lift of 32 pounds once a minute.)
  
  
• Rest breaks or other tasks should follow each 15-minute period of lifting.
  
  

5. Training

• Workers should be trained in proper lifting techniques.
  
  

Ultraviolet radiation

Ultraviolet radiation is a physical process for disinfection. Electromagnetic energy from a light source is transferred to cellular material that prevent cell replication. The skin and eyes easily absorb UV radiation that can cause injury. Personal protective equipment must be used and should include wrap around goggles or a face shield that will absorb UV wavelengths.

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