Chapter 5 - Physical Agents

Physical Agents

what is a physical agent?

Sources of energy that may cause injury or disease

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may be ambient or acute

what are examples of physical agents?

• radiation

• noise

• vibration

• extremes in temperature and pressure

ambient (physical agent)

• All-encompassing condition associated with a given environment

• Composite of inputs from sources all around us

• Example: ambient noise could be the ventilation in the classroom

acute (physical agent)

Resulting from a single exposure

what are the 2 groups of radiation and how are they identified?

• 2 groups: ionizing & non-ionizing

• Identified by wavelength and their action on tissue

what is ionizing radiation?

• Electromagnetic energy capable of producing ions through interaction with matter

• X-rays (commonly found in medical facilities)

• Gamma rays, alpha particles, beta particles, and neutrons (commonly found in nuclear operations or research companies)

• measured in rem

how to control exposure of ionizing radiation?

Control of exposure will include:

• regular monitoring

• shielding

• job rotation

• protective equipment

• extensive training

what are the effects of ionizing radiation?

• Effects of electromagnetic radiation upon humans and animals depend upon the power and frequency of the radiation

• Biological effects depend on if the exposure is whole body/local or acute/chronic

• Genetic effects: cell mutation, burns, and radiation sickness

what is non-ionizing radiation?

• Electromagnetic radiation that does not have energies great enough to ionize matter:

  • Ultraviolet radiation

  • Visible (white light) radiation

  • Infrared radiation

  • Microwave radiation

  • Radio waves

• Sun can be a source of all these radiations

how to control non-ionizing radiation?

• isolation or separation

• protective equipment

• training

the impact of non-ionizing radiation depends on:

• amount of exposure

• power density of the field of the beam

• environmental conditions

what is a dosimeter?

Electronic personal meters allow workers to measure the levels of ionizing radiation they are exposed to

what are engineering controls of radiation?

• shields

• walls

• locked doors

• warning indicators

• displays

• ventilation systems

what are administrative controls of radiation?

• regular inspections and maintenance schedules

• operating procedures

• proper labelling and inventory of any radioactive devices or materials

what are PPE controls of radiation?

• lead aprons

• vests

• air-purifying respirators

• eye protection

what is radiation half-life?

• The intensity of a radioactive source diminishes over time and radioactive atoms decay and eventually form more stable atoms

• Radiation half-life: to measure the amount of time required for the intensity of radiation from a radioactive source to be reduced by half

  • Tells us the amount of radioactivity that is left in a substance or object – indicating the level of risk/danger

what is noise?

• Any unwanted sound

• Most common workplace hazard

• Standards for measurement: decibel (dB)

what is early warning change?

• A deterioration of hearing in the upper frequency

• the earliest detectable sign of noise-induced hearing loss

what is threshold of hearing?

Range of sound that human ear can perceive or hear

hearing response is conditional on 3 characteristics:

• frequency

• duration

• loudness

noise can cause:

• Physiological damage (noise-induced hearing loss)

• More general physiological effects (ex. headaches)

• Psychological effects

infrasound (inaudible sound with frequency <20Hz) reported to cause “vertigo, imbalance…intolerable sensations, incapacitation, disorientation, nausea, vomiting and bowel spasm)

what are the 2 types of physiological damage of hearing loss?

• conductive hearing loss

• sensorineural hearing loss (nerve deafness)

what is conductive hearing loss?

• Restricts transmission of sound to cochlea or inner ear

• Commonly caused by wax buildup, infection or trauma

what is sensorineural hearing loss?

• Affects the cochlea

• Usually irreversible

• Can occur randomly

what is NIHL & its factors?

noise-induced hearing loss

• Typically a cumulative process

• Factors: loudness and amount of exposure

what are indications of exposure to excessive noise levels?

• Ringing in ears (tinnitus)

• Raising volume on radio or TV

what is temporary threshold shift (TTS)?

• Temporary reduction in hearing sensitivity

• Gradual hearing loss

• Can sometimes be reversed by removal from noise source

what is permanent threshold shift (PTS)?

Hearing disability that is permanent and may not be correctable

noise exposure standards

vary across provinces and territories

what are some noise exposure test equipment?

• sound pressure meter level (Decibel meter)

• octave band analyzer

• audiometer

what is a sound pressure level meter?

• decibel meter

• Measures gross noise level

what is an octave band analyzer?

• Measures noise level in each frequency range

• Far more expensive and less commonly used

what is an audiometer?

• Instrument used to determine sensitivity of a person’s hearing

• Tests your ability to hear sounds; does not measure noise levels

source of noise

• Make source quieter

E.g., a noisy machine may be made quieter by:

• Adding sound-absorbing material

• Placing vibration padding under it

• Redesigning the operation so the machine performs differently

• isolating machine in a separate room or sound-deadening enclosure

• Purchasing a new (usually higher quality) machine

path of noise

• Move worker away from source and/or erect sound barriers between noise and worker

• As the distance from the sound source is doubled, the noise level will drop by a fixed amount

• Attenuation: reduction of noise at one location compared with another father from the source

human of noise

• PPE

• Least costly and most commonly used

• Not always the best method

• Many companies are not well informed to undertake other approaches:

  • Job rotation

  • Relocation

  • Isolation

  • Automation

  • Rest periods

  • Site design

what is vibration?

Oscillating motion of body moving about a reference position

what is resonance?

Object reacts strongly to some particular frequency

what is segmental vibration?

• Vibrations that affect only parts of the body

• AKA: hand-arm vibration

what is whole-body vibration (and health effects)?

• Affects the whole body as a unit

• Health effects:

  • Inhibition of muscular reflexes

  • Impaired or blurred vision

  • Alterations of brain electrical activity

what are health effects of vibration?

• Sore neck and shoulder muscles

• Sore joints

• Raynaud’s phenomenon, or white fingers, caused by restricted blood circulation in the fingers

• Neuritis and degenerative alterations of CNS

• Necrosis (death or decay of tissue)

• Decalcification of the carpal bones (loss of calcium)

• Muscle atrophy and tenosynovitis (inflammation of the sheath surrounding a tendon)

what is thermal stress?

• Cold and hot temperatures extremes coupled with high humidity

• Homeostasis

  • Basis for examining the effects of heat and cold on the body

  • Balance of heat generation

what are the 3 methods of heat gain or loss?

• conduction

• convection

• radiation

what is conduction?

When two surfaces are in contact (e.g., the skin touches a hot stove, resulting in a local burn)

what is convection?

When one surface adds heat to the surroundings (e.g., the skin is close to air flow emanating from a heater)

what is radiation? (heat gain/loss)

When energy is transmitted by electromagnetic waves (e.g., the skin is exposed to sunlight)

what are some heat-related illnesses?

• heat edema

• heat rash

• heat cramps

• heat stroke

• heat exhaustion

what is heat edema?

fluid pools in hands or legs

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In individuals who are not acclimatized to working in hot environments

what is heat rash?

blocked sweat ducts trap sweat under skin

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One of the first signs of the body’s intolerance to heat

what are heat cramps?

muscle spasms from electrolyte imbalance

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Occur in the muscles and may or may not occur in conjunction with other heat-related illnesses

what is heat stroke?

inadequate amount of blood in the brain due to lowered blood pressure

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Often occurs while an individual is standing or working

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Symptoms: either a partial or complete loss of consciousness & skin remains moist

what is heat exhaustion?

Occurs when an individual is sweating excessively and loses too much body water

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Symptoms: excessive sweating, dizziness, blurred vision, nausea, headache, vomiting, heart palpitations, and numbness in the hands or feet

what are the 2 levels of heat stroke?

• classical

• exertional

what is classical heat stroke?

Major disruption to the CNS functions and often includes a lack of sweating

what is exertional heat stroke?

Occurs in individuals who are physically active and may continue to sweat

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Skeletal muscle can rapidly break down and can result in kidney and heart failure

what are engineering controls for controlling heat?

Most effective method but often impractical in certain environments (ex. outdoors)

• Insulating heat sources or hot surfaces

• shielding or protecting workers

• providing air conditioning

• increasing ventilation

what are administrative controls for controlling heat?

• Reducing worker activity

• proper supervision

• arranging for work-rest cycles

• implementing work methods or requirements that help acclimatize workers (e.g., physical fitness, drinking water)

what are PPE controls for controlling heat?

• Eye protection, cooling vests, hats and sunblock

• Should be used in combination with other administrative and engineering controls

what are risk factors for cold-related illnesses?

• Age

• gender

• fatigue

• diseases

• health conditions

• consuming drugs or alcohol

• smoking

what are non-freezing injuries?

temperatrues above freezing mark

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Happen in body parts such as hands and feet cool but do not freeze

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Ex: Chilblains: painful inflammation of small blood vessels in your skin, immersion foot and trench foot

what are freezing injuries?

Occur in colder temperatures and care caused by local freezing of muscles and tissues

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ex. frostnip (ear lobes, nose, cheeks, fingers, and toes), frostbite (restricted blood flow to the tissues)

what is hypothermia?

Occurs when cold causes the body’s ability to regulate its thermal temperature to fail and the body is not able to compensate for the loss of heat

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Requires immediate first aid and treatment of symptoms

what are engineering controls for controlling cold?

Heaters and shields that protect an individual from the cold environment or object

what are administrative controls for controlling cold?

• Work and rest schedules

• cold-weather procedures such as shutdown or closure requirements

what are PPE controls for controlling cold?

clothing