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Introduction to Industrial Hygiene

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Title: Introduction to Industrial Hygiene


1
Introduction to Industrial Hygiene
  • Safety Management
  • TM 650
  • Carter J. Kerk
  • Industrial Engineering Department
  • South Dakota School of Mines
  • Summer 2007

2
Introduction to Industrial Hygiene
  • Read Asfahl
  • Chapter 9, Health and Toxic Substances
  • Chapter 10, Environmental Control and Noise

3
Industrial Hygiene
  • Part science, part art
  • Industrial Hygiene is the application of
    scientific principles in the workplace to prevent
    the development of occupational disease or injury
  • Requires knowledge of chemistry, physics,
    anatomy, physiology, mathematics

4
IH Topics
  • Toxicology
  • Occupational Health Standards
  • Airborne Hazards
  • Indoor Air Quality
  • Skin Disorders
  • Noise Exposure
  • Radiation
  • Thermal Stress
  • Anatomy
  • Biohazards
  • Chemicals
  • Illumination
  • Personal Protective Equipment
  • Ventilation
  • Vibration
  • Sampling

5
History of IH
  • Disease resulting from exposure to chemicals or
    physical agents have existed ever since people
    chose to use or handle materials with toxic
    potential
  • In the far past, causes were not always recognized

6
Earliest Recordings
  • Lead poisoning among miners by Hippocrates, 4th
    century BC
  • Zinc and sulfur hazards by Pliny the Elder, 3rd
    century BC

7
The Original Metallica
  • Georgius Agricola published a 12 volume set in
    1556, De Re Metallica
  • Town physician in Saxony
  • Silver mining
  • Described diseases of lungs, joints, eyes
  • Woodcuts (see next slides)

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11
Metallica Quotes
  • If the dust has corrosive qualities, it eats
    away at the lungs, and implants consumption in
    the body
  • Later determined to be silicosis, tuberculosis,
    and lung cancer

12
Metallica Quotes
  • there is found in the mines black pompholyz,
    which eats wounds and ulcers to the bone this
    also corrodes iron . . . There is a certain kind
    of cadmia which eats away at the feet of workmen
    when they have become wet, and similarly their
    hands, and injures their lungs and eyes.
  • Later recognized as manifestations of toxicity of
    arsenic and cadmium

13
Metallica cont.
  • A young American named Herbert C. Hoover and his
    wife, L.H. Hoover, translated Agricolas work
    into English.
  • The translation was published in 1912
  • Hoover graduated from Stanford in 1891 as a
    Mining Engineer
  • Hoover served as the 31st president of the US
    (1929 1933)

14
Paracelsus
  • Published work describing mercury poisoning of
    miners in 1567
  • His famous quote, All substances are poisons
    there is none which is not a poison. The right
    dose differentiates a poison and a remedy.
  • This provided the basis for the concept of the
    dose-response relationship.

15
Dose-Response Relationship
  • The toxicity of a substance depends not only on
    its toxic properties, but also on the amount of
    exposure, or the dose
  • Paracelsus differentiated between
  • Chronic (low-level, long-term) poisoning
  • Acute (high-level, short-term) poisoning

16
Bernardino Ramazzini (1633-1714)
  • Wrote a book, De Morbis Artificum (Diseases of
    Workers), starting the field of occupational
    medicine
  • Urged physicians to ask the question, Of what
    trade are you?
  • He described diseases associated with various
    lower-class trades, such as corpse carriers and
    laundresses.

17
Other Pioneers around 1770
  • Sir George Baker
  • Linked Devonshire colic to lead in cider
  • Percival Pott
  • Linked soot exposure and scrotal cancer in
    chimney sweeps

18
The Mad Hatter
  • Lewis Carrolls Alice in Wonderland (1865)
  • Mad Hatter exhibited symptoms of mercury
    poisoning, such as mental and personality changes
    marked by depression and tendency to withdraw
  • Mercury was used in processing hides made into
    hats
  • Bars were installed on windows at hat factories
    presumably to prevent afflicted workers from
    leaping during bouts of depression

19
Protection Starts to Arrive
  • English Factory Act, 1833, allows injured workers
    to receive compensation
  • English Factory Inspectorate, 1878
  • US Workers Compensation started in 1908-1915 in
    several states (state programs, not federal)
  • Occupational Safety Health Act enacted in 1970
    creating OSH Administration
  • Created regulations, inspections, recordkeeping,
    enforcement, etc.

20
Birth of Industrial Hygiene
  • A few industrial hygienists were practicing in
    early 1900s
  • Physicians sometimes saw the industrial hygienist
    as a threat to their realm of expertise
  • Dr. Alice Hamilton was a pioneer Occupational
    Physician and female pioneer. She helped foster
    the field of IH in the US
  • American Industrial Hygiene Association (AIHA)
    formed in 1939

21
Industrial Hygiene
  • Other terms
  • Occupational Hygiene
  • Environmental Hygiene
  • Environmental Health

22
Professional Organizations
  • American Industrial Hygiene Association (AIHA),
    www.aiha.org, member organization
  • American Conference of Governmental Industrial
    Hygienists (ACGIH), www.acgih.org, member
    organization for government employees
  • American Board of Industrial Hygiene (ABIH),
    www.abih.org, independent organization that
    administers certification programs for industrial
    hygiene professionals
  • IHIT, Industrial Hygienist in Training
  • CIH, Certified Industrial Hygienist
  • Requires maintenance of certification

23
Scope of IH
  • Recognition, Evaluation, and Control of hazards
    or agents
  • Chemical Agents
  • Dusts, mists, fumes, vapors, gases
  • Physical Agents
  • Ionizing and nonionizing radiation, noise,
    vibration, and temperature extremes
  • Biological Agents
  • Insects, molds, yeasts, fungi, bacteria, viruses
  • Ergonomic Agents
  • Monotony, fatigue, repetitive motion

24
Control of Agents
  • Controls in this order of preference
  • Engineering Controls
  • Engineering changes in design, equipment,
    processes
  • Substituting a non-hazardous material
  • Administrative Controls
  • Reduce the human exposure by changes in
    procedures, work-area access restrictions, worker
    rotation
  • Personal Protective Equipment / Clothing
  • Ear plugs / muffs, safety glasses / goggles,
    respirators, gloves, clothing, hard-hats

25
1. Recognition of health hazards
  • Walk-through survey with someone knowledgeable of
    the processes
  • Regular intervals, keep records
  • Planning stage reviews
  • Modification reviews
  • MSDS reviews

26
2. Evaluation of hazards
  • Measurements
  • Air sampling, noise meters, light meters, thermal
    stress meters, accelerometers (vibration)
  • Calculation of dose
  • Level and duration of exposure
  • Keep records

27
3. Control of Hazards (Prioritized)
  • 1 Engineering
  • Substitute a less hazardous material, local
    exhaust ventilation
  • 2 Administrative
  • Worker rotation, training
  • 3 Personal Protective Equipment
  • Respirators, gloves, eye protection, ear
    protection, etc.

28
4. Recordkeeping
  • Important in all phases of the program
  • Often required by regulation
  • 29 CFR 1904
  • Increase program effectiveness
  • Useful in legal challenges

29
5. Employee training
  • Effective component if total program is
    implemented and engineering controls are first
    established
  • Often required by regulation
  • Right to Know or Hazard Communication Standard
    29 CFR 1910.1200
  • Regular intervals
  • Keep it interesting and effective, use a variety
    of techniques
  • Keep records of dates, individuals, topics,
    effectiveness

30
6. Program review
  • Regular intervals (yearly, semi-annual)
  • Review the written program as well as the
    implementation
  • Updates for new regulations, new chemicals, new
    processes, or any changes
  • Audit components of the program
  • Internal OSHA inspection
  • Involve employees, consultants, management

31
Toxicology

32
Definitions
  • Toxicity The ability of a substance to cause
    harm or adversely affect an organism
  • Toxicology The science and study of harmful
    chemical interactions on living tissue

33
Occupational Toxicology
  • Workplace exposure to chemicals
  • You or someone you know has probably experienced
    an episode of toxicology
  • Injury or death due to
  • Smoke inhalation
  • Confined space incident
  • Ingestion or absorption of a chemical

34
The Dose-Response Relationship
  • A time of exposure (dose) to a chemical, drug, or
    toxic substance, will cause an effect (response)
    on the exposed organism
  • If the amount or intensity of the dose increases,
    there will be a proportional increase in the
    response

35
Definitions
  • Dose The amount of a substance administered (or
    absorbed), usually expressed in milligrams of
    substance per kilogram of the exposed organism
    (mg/kg)
  • Response The effect(s) of a substance may be
    positive or negative

36
Dose Response Curve
37
Acute and Chronic Terminology Exposure as well
as Response
  • Acute exposure short time / high concentration
  • Chronic exposure long-term, low concentration
  • Acute response rash, watering eyes, cough from
    brief exposure to ammonia
  • Chronic response emphysema from years of
    cigarette smoking

38
Possible Response Levels
  • No response at low dosage levels there may be
    no response at all
  • Threshold dose the lowest level of dosage at
    which a response is manifested
  • NOAEL no observed adverse effect level
  • NEL no effect level
  • Above threshold dose response can be positive
    up to a point and then could become toxic to the
    organism
  • Different people or organisms will exhibit a
    variety of responses

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Indicators of Relative Toxicity
  • Toxicity ability of a substance to cause harm or
    have an adverse affect
  • How much harm?
  • What aspect of the population?
  • Notation
  • LD, lethal dose
  • LC, lethal concentration
  • ED, effective dose
  • EC, effective concentration

41
LD50 a measure of relative toxicity
  • Most common toxicity notation
  • Determined in the lab and based on an acute
    exposure to adult test animal
  • Lethal dose that produces death in 50 of the
    exposed population
  • LD50, 35 mg/kg, oral, rat
  • 35 mg of dose per kg of rats body weight, when
    administered orally, produces death in 50 of
    exposed population
  • Comparing the LD50 between two substances gives
    the relative toxicity between the two substances

42
LD50 Relative Toxicity
Agent LD50 (mg/kg)
Ethyl Alcohol 10,000
Sodium chloride 4,000
Morphine sulfate 900
Strychnine sulfate 2
Nicotine 1
Hemicholinium-3 0.2
Dioxin (TCDD) 0.001
Botulinum toxin 0.00001
43
Effect of route of administration
44
How can we interpret animal test?
  • Animal tests can give an indication of relative
    toxicity which can be extrapolated to humans
  • Problems
  • Toxicity variance between organisms
  • Animal doses (strength or time) may be higher
    than realistic human exposures
  • On a body weight basis, humans are usually more
    susceptible to toxic effects, sometimes by a
    factor of ten
  • Therefore, human interpretation requires use of a
    safety factor

45
Epidemiological Studies
  • Prospective epidemiological study
  • Take a cohort (or group of individuals) with a
    common exposure
  • Follow through time to see if they develop
    disease
  • Retrospective epidemiological study
  • Take a cohort with a disease and trace back
    through time to see if there is a common exposure
  • These are difficult with many confounding
    factors, but are quite valuable

46
Latency Period
  • Long delay between exposure and disease
  • Some diseases may not develop for many years
  • Lung cancer may occur as much as 30 years after
    exposure to asbestos
  • This makes animal studies and epidemiological
    studies even more difficult, but also very
    valuable

47
Routes of Exposure
  • Inhalation
  • Ingestion
  • Absorption through the skin
  • Less common
  • Injection
  • Absorption through eyes and ear canals

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Inhalation
  • Most common route of entry into body
  • Therefore our area of highest concern
  • Lungs are designed for efficient gas exchange
    between the air and bloodstream
  • Lungs have up to 1000 square feet of exchange
    area (about 32 feet by 32 feet)
  • Normal days breathing volume 8 cu ft
  • Therefore great potential for toxins to enter
    bloodstream

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Skin Absorption (2nd most important route)
  • Skin surface area is about 20 square feet (4.5 ft
    by 4.5 ft)
  • Compare to 1000 sq ft for lungs
  • Materials can be absorbed into blood stream just
    below the skin surface or toxins can be stored in
    fat deposits
  • Obviously workers can easily expose their hands
    into solvents, oils, chemicals, etc., plus these
    materials can be sprayed or rubbed on other parts
    of the body
  • Many chemicals are either soluble in water or in
    oil (fat, lipid)
  • The skin easily absorbs lipid-soluble materials
  • Solvents
  • Water-soluble materials are not easily absorbed
  • Lipid layer on skin provides a barrier

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Ingestion (3rd most important route)
  • Ingestion is not usually intentional
  • Unintentional ingestion
  • Failure to wash hands and face before meals
  • Eating/drinking in areas where airborne hazards
    exist
  • Lighting cigarettes with dirty hands
  • Application of cosmetics
  • Use of chewing tobacco or gum in contaminated
    areas

54
Ingestion
  • The digestive tract is moist and designed for
    efficient absorption
  • Surface area of intestines is greatly increased
    by small projections (villi)
  • Thin surfaces, highly vascularized
  • Materials easily transferred to bloodstream

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Injection
  • Less common
  • Possible hazards
  • Outdoor work, construction sites, hazardous waste
    sites, plants, animals, reptiles, insects,
    abrasions, puncture wounds, cuts

57
Absorption into eyes and ears
  • Much less common but possible
  • Moist surfaces

58
Distribution of Toxins
  • Once toxins are in the body, there are several
    mechanism of movement and action
  • Inhalation
  • Toxics may enter bloodstream
  • Toxics may irritate or scar lung tissues directly
  • Skin Absorption
  • Toxics may enter bloodstream
  • Toxics may irritate, corrode or burn skin directly

59
Once absorbed into the body, toxins can move to
other tissues and organs through various ways
  • Filtration
  • Toxins move through membrane pores
  • Diffusion
  • Movement from higher concentration to lower
    concentration
  • Active transport
  • Movement across a membrane otherwise impermeable
    by a transport mechanism
  • Chemical reaction or carrier molecule, requires
    energy
  • Phagocytosis
  • Toxins eat or engulf other cells or by use of
    white blood cells

60
Liver
  • Important in metabolism, energy storage, protein
    synthesis
  • Receives blood from digestive tract and works to
    concentrate, transform, and excrete substance
    (both good and bad toxins)
  • Thus produces bile (enriched) which is returned
    to the intestines

61
Kidneys
  • Receive 25 of cardiac output for filtration
  • Primarily for elimination of water soluble
    molecules
  • Large molecules (proteins) and lipid soluble
    materials are reabsorbed through the tubules of
    the nephron
  • Nephron functional unit of the kidney (see next
    slide
  • Materials pass by filtration, diffusion, active
    transport

62
Classes of Toxins and Toxic Responses
  • Irritants and Sensitizers
  • Systemic Toxins
  • Neurotoxins
  • Reproductive Toxins
  • Carcinogens

63
Occupational Health Standards

64
Exposure Limits
  • Mainly concerned with air quality values in the
    workplace
  • Air concentration below which health hazards are
    unlikely to occur among most exposed workers
  • Based on scientific studies (animal, human)
  • Other topics noise, electromagnetic fields,
    ionizing radiation, etc.

65
Sources of Exposure Limits
  • OSHA limits are the only ones enforceable as law
  • Other sources
  • NIOSH
  • ANSI (American National Standards Institute)
  • ASTM (American Society for Testing Materials)
  • ACGIH
  • AIHA

66
Exposure Limit Terms
  • TWA Time-Weighted Average
  • 8 hour, 15 minute, 5 minute, instantaneous
  • 8-Hr TWA (CxTx)(CnTn)/8
  • Cx concentration measured during time interval
    Tx
  • n total number of intervals measured
  • Make sure time intervals in numerator match time
    in the denominator
  • Concentrations
  • Parts per million (ppm) gases, vapors
  • Milligrams per cubic meter (mg/m3) solids
    (fumes, dusts, mists)

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OSHA PELs
  • OSHA PELs are found in Tables Z-1 and Z-2 of
    29CFR1910 Subpart Z
  • Use these to look up substance-specific standards

71
Example PELs (Table Z-1)
Substance PPM Mg/m3
Ammonia 50 35
Carbon Dioxide 5000 9000
Carbon Monoxide 50 55
Chlorine (C) 1 (C) 3
Notes PELs are 8-hr TWA unless otherwise noted.
C refers to ceiling limit
72
Example Benzene PEL
  • Table Z-2
  • 8-hr TWA 10 ppm
  • Acceptable ceiling concentration 25 ppm
  • Acceptable max peak above acceptable ceiling
    concentration for an 8-hr shift 50 ppm for 10
    min
  • See 29CFR1910.1028 for more specific standards on
    benzene

73
Carcinogens
  • Substances known to cause cancer
  • NIOSH uses notation Ca
  • OSHA addresses carcinogens through
    substance-specific regulations
  • ACGIH uses a 5 category system
  • A1 through A5

74
Respiratory Protection Standard
  • 29 CFR 1910.134
  • Assign responsibility for program
  • Written procedures on selection, use and care of
    respirators
  • Medical surveillance program
  • Employee training on use, care and limitations of
    respirators
  • Fit testing appropriate for contaminants

75
Respiratory Std Cont.
  • Procedures for cleaning, storing, maintaining,
    and inspecting respirators
  • Periodic monitoring of contaminant levels
  • Periodic review of the program for effectiveness

76
HAZWOPER
  • Hazardous Waste Operations and Emergency Response
    Standard
  • 29 CFR 1910.120 (1926.69 Construction)
  • Ensure health and safety of workers at sites
    where hazardous materials have been either
    accidentally released or dumped or where they are
    treated, stored, or disposed of.

77
Confined Space Standard
  • 29 CFR 1910.146
  • Confined Space
  • Large enough to enter and perform work
  • Limited or restricted means for entry or exit
  • Not designed for human occupancy
  • Permits

78
Occupational Noise Exposure Standard
  • 29 CFR 1910.95

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Airborne Hazards

81
Introduction
  • Route of entry Airborne hazards are the most
    serious concern
  • Processes welding, grinding, spraying, hot
    processes, engine exhausts
  • Pollen, spores
  • Lungs efficient transfer of gases in and out of
    the body
  • But also provide a route of entry for hazards

82
Anatomy Function of the Lungs
  • Regions of the respiratory tract
  • Upper (nasopharyngeal)
  • Middle (tracheobronchial)
  • Lower (distal)

83
Upper (Nasopharyngeal)
  • Head, nose, nasal passages, sinuses, mouth,
    tonsils, epiglottis, back of throat
  • Lined with mucous membrane
  • Moist, sticky substance captures materials
  • Many small hairs
  • Help to trap particles

84
Middle (Tracheobronchial)
  • Trachea (windpipe), bronchi
  • Rings of cartilage and muscle
  • Cartilage provides structural support
  • Muscles contract to help force air
  • Coughing, sneezing
  • Lined with mucous membrane and hairs (cilia)
  • Cilia move like waves to push mucus and particles
    upward
  • Cigarette smoking can paralyze the cilia
  • Particle-laden mucus is removed by coughing,
    expectorating, or swallowing

85
Lower (Distal)
  • Bronchi split (bifurcate) repeatedly into two
    smaller passages (17 times) called bronchioles
  • Diameters decrease accordingly
  • Bronchioles end in microscopic sacs called
    alveoli (site of gas exchange)
  • Alveolar membrane is one cell thick
    (pneumocytes), surrounded by capillaries
  • Passive diffusion

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Microns (Micrometer)
  • One thousandth of a millimeter
  • 0.001 mm 1 mm
  • Greek letter, m
  • Useful in discussion of the size of inhaled
    particles
  • Visible to human eye
  • gt 100 mm 0.1 mm 0.01 cm
  • Human hair diameter
  • 5 500 mm 0.005 0.5 mm

90
Protective Mechanisms of the Respiratory Tract
  • Larger particles (gt10 mm)
  • Removed in nose and upper airways
  • 5 10 mm
  • Captured in tracheal region
  • 3 5 mm
  • Contact mucus lining in tracheal or bronchi
  • 0.5 3 mm
  • Can reach alveolar region, but few do

91
Capture of particles
  • Mucus (moist, sticky) linings
  • Tortuous pathway
  • Multitude of branches and splits
  • Large surface area of the route
  • Once particles are captured in mucus, they are
    removed by the mucociliary elevator or ladder
  • Cough reflex

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Protection in the Alveolar Region
  • Primary defense macrophages (specialized white
    blood cells)
  • Engulf foreign objects and attempt to dissolve
    them
  • The smallest of particles may pass through cell
    membranes and lodge between cells (interstitial
    space)

94
Airborne Hazardous Materials
  • Aerodynamic Diameter
  • Useful for comparing particles with irregular
    shapes (dusts, fibers, etc.) to particles with
    regular shapes (droplets, mists, etc.)
  • The diameter of a reference spherical particle
    with a unit density of one (1) that has the same
    settling velocity as the contaminant particle

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Classes of Airborne Materials
  • Particulates / aerosols
  • Solid particles, dusts, fibers, mists, droplets,
    fumes
  • Gases / vapors
  • Gaseous contaminants, vapors
  • Oxygen-deficient atmospheres
  • lt 19.5 oxygen
  • Combination
  • Any combination of particulates and/or gases,
    including oxygen-deficient atmospheres

97
Effects of Inhaled Materials
  • Airborne toxins
  • Local effects on tissues
  • Ammonia irritation in respiratory tract
  • Systemic effects through blood transport
  • Carbon tetrachloride (liver)
  • Solubility
  • More soluble upper respiratory tract, moist
    tissue around eyes ammonia
  • Less soluble penetrate to middle and lower
    respiratory tract phosgene gas

98
Occupational Diseases Associated with Airborne
Particulates
  • Pneumoconiosis
  • Physiological Responses
  • Mineral Fibers and Other Fibers
  • Metals
  • Organic Particles

99
Indoor Air Quality

100
IAQ Outline
  1. Introduction
  2. Indoor air quality as a public health concern
  3. Heating, ventilating, and air conditioning
    systems (HVAC)
  4. Basic instruments for use in IAQ studies
  5. Microorganism contamination and IAQ
  6. Radon and asbestos

101
Introduction
  • Indoor Air Quality (IAQ)
  • Recent phenomenon
  • Due to construction of energy conservation
    construction techniques starting in the 1970s
  • Sick Building Syndrome
  • Tight Building Syndrome
  • Gases emitted from cleaning chemicals, building
    materials, office furniture, carpets
  • Radon, asbestos, Legionella (put Rapid on the
    national map!)
  • Industrial and Non-Industrial (e.g., schools)
  • Ventilation Issues

102
Indoor Air Quality as a Public Health Concern
  • The energy crisis in the 1970s spawned
    construction of thousands of energy efficient
    buildings
  • Sealed windows
  • Thermostats not accessible or adjustable by
    occupants
  • Self-contained environments with controls for
    temperature, humidity, airflow
  • Complaints odors, too hot, too cold
  • Physical symptoms headaches, respiratory
    irritation

103
Temperature
  • Too hot, too cold, too drafty
  • Conditions vary with seasonal changes and HVAC
    operation

104
Humidity
  • Air is too dry
  • Contributing to irritation of the respiratory
    tract and eyes
  • Too much humidity
  • Contributes to growth of microorganisms,
    encourages odors and mustiness

105
Stuffiness or Lack of Circulation
  • Can be related to location of diffusers or
    outlets relative to occupants
  • HVAC system is undersized, poorly maintained, or
    improperly operated
  • Poor circulation can lead to stratification of
    air
  • Some areas benefit, other areas suffer
  • Dead zones may allow odors and CO2 to accumulate
    to unacceptable levels

106
Odors
  • Many objectionable odors coffee, body odor,
    vehicle exhaust, chemical smells
  • New construction or renovation odors fresh
    paint, off gassing from furniture or carpet
    fabric (formaldehyde)
  • Odors may be drawn in from outside
  • Air intakes located near loading docks, trash
    dumpsters, incinerators, exhaust stacks

107
Physical Symptoms
  • Dryness of eyes and respiratory tract, headaches,
    tiredness, upset stomach, runny nose, nasal
    congestion, drowsiness
  • CO2 levels gt 1000 ppm may cause headaches and
    drowsiness
  • Symptoms are often non-specific enough to draw a
    cause-effect relationship

108
US Statistics on IAQ
  • About half of IAQ problems were attributed to the
    HVAC system
  • Poor system design
  • Poor maintenance
  • About 40 due to chemical contaminants or
    microbes
  • In 10 of the cases, no cause could be found

109
Psychosocial Factors
  • Do not disregard this category
  • Job satisfaction, degree of control over ones
    environment, window placement and window control

110
OSHA Standards for IAQ
  • On December 17, 2001, OSHA withdrew its IAQ
    proposal and terminated rulemaking proceedings
  • Proposed
  • CO2 lt 800 ppm
  • RH lt 60
  • Maintain HVAC records on original design
    specifications, cleaning, repairs
  • Exhausting designated smoking area to the outside
    and keeping them under negative pressure
  • Locating air intakes of systems to prevent
    capturing outside air contaminants

111
ASHRAE
  • American Society of Heating, Refrigerating, and
    Air-Conditioning Engineers
  • www.ashrae.org
  • 62-1989, Ventilation for Acceptable Air Quality
  • 55-1992, Thermal Environmental Conditions for
    Human Occupancy
  • 52-1992, Methods of Testing Air Cleaning Devices
    Used in General Ventilation for Removing
    Particulate Matter

112
Fresh Air Recommendations
  • ASHRAE Recommendations
  • 1905 30 cfm / person
  • 1936 10 cfm / person
  • 1973 5 cfm / person
  • Energy crisis concerns
  • 1989 20 cfm / person
  • Concerns about 2nd hand smoke

113
Basic Instruments for IAQ Studies
  • Thermometer
  • Velometer (air velocity)
  • Rotating vane anemometer
  • Heated-wire anemometer
  • Gas Detection Instruments
  • Detector tubes
  • Psychrometer (relative humidity)
  • Smoke tubes
  • IAQ multi-function instruments
  • Air temperature, humidity, CO2, air velocity,
    dewpoint, computer interface

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Occupational Noise Exposure

115
Outline Occupational Noise Exposure
  • Physics of sound
  • Anatomy of the ear
  • Evaluating hearing ability and hearing loss
  • Standards for occupational noise exposure
  • Measuring noise in the occupational setting
  • Controlling noise

116
Introduction
  • High levels of noise cause hearing loss
  • Hearing loss is mostly irreversible and usually
    preventable
  • Noise can also produce stress, reduce
    productivity, and cause communication problems

117
Physics of Sound
  • Noise unwanted sound
  • Energy in the form of pressure waves
  • Waves can be described by frequency (f), speed
    (c), and wavelength (?)
  • c f ?
  • Sound moves at 344 m/sec in air, 6100 m/sec in
    steel
  • Some materials will amplify or reflect sound
  • Frequency (f) is related to pitch
  • Healthy, young person can detect 20 to 20,000 Hz
    (cycles/sec)
  • This declines with age and exposure history

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Sound Pressure Level
  • We can measure sound pressure
  • Force per unit area
  • SI units, pascal, Pa
  • All sound pressures are related to a reference
    sound pressure of 20 ?Pa (approximate lower
    threshold for human hearing at 1000 Hz)
  • Lp 20 log10 (P / 20 ?Pa)
  • Where Lp is the sound pressure, in decibels (dB)
  • P is the measured sound pressure, in Pa
  • The decibel is a dimensionless quantity based on
    the logarithm of a ratio and gives a more
    convenient range of values than would Pa

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Weighting Scales A, B, C
  • Each scale approximates the response of the human
    ear at different ranges of pressure
  • Because the human ear does not hear sound as if a
    machine. The human ear is more sensitive to
    higher frequencies
  • Derived from comparison experiments
  • Example a noise of 1000 Hz frequency and an SPL
    of 20 dB sounds as loud as a noise of 25 dB at
    500 Hz
  • A-Scale is most common and referenced by OSHA
    regs
  • B-Scale rarely used (medium sound pressure
    levels)
  • C-Scale common for evaluating explosions and
    impact noise

122
Anatomy of the Ear
  • Outer ear and ear canal directs and amplifies the
    sound by 10-15 dB
  • Sound pressure waves impact on the ear drum and
    vibrate the three tiny bones in the middle ear
  • Malleus (hammer)
  • Incus (anvil)
  • Stapes (stirrup)
  • Which vibrates against the oval window leading to
    the inner ear

123
Inner Ear
  • Cochlea (inner ear)
  • Basilar membrane (lining of the cochlea)
  • Supports 25,000 specialized hair cells
  • Which send characterizing nerve impulses to the
    brain
  • Three semicircular canals (in orthogonal planes)
  • Filled with fluid
  • Provides sense of balance and relative body
    position
  • Have you ever felt dizzy?
  • Eustachian tube
  • Connects middle ear to throat
  • Equalizes pressure
  • Have your ears ever popped?

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Hearing Loss
  • Conductive hearing loss
  • Interruptions along the pathway reducing hair
    stimulation
  • Excessive earwax, otitis media (fluid in middle
    ear), ruptured eardrum
  • Sensory hearing loss
  • Presbycusis (loss due to age)
  • Noise-induced hearing loss
  • Sociacusis (loss from everyday life)
  • Nosacusis (loss from disease, heredity, drugs,
    sudden and severe pressure changes, traumatic
    head injuries)
  • Tinnitus (follows traumatic exposure to loud
    noise perceived ringing, roaring, hissing may
    be permanent)

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Evaluating Hearing Ability and Hearing Loss
  • Audiograms
  • A hearing evaluation exam, called audiometry,
    produces a report called an audiogram
  • OSHA requires all workers exposed to an 8-hour
    TWA of at least 85 dBA (Action Level) receive a
    baseline audiogram and annual follow-up exam
  • Employee sits in soundproof booth with headphones
    and control button to produce HTL (Hearing
    Threshold Level)
  • Method of Limits at the following test
    frequencies 500, 1000, 2000, 3000, 4000, 6000
    Hz, the range most detectable by the human ear
  • Speech range 1000 4000 Hz

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Reasons for Variation in Audiometric Testing
  • Ear wax buildup
  • Head cold, congestion
  • Confusion about response procedure
  • Incorrect placement of headphones
  • Hair under headphones
  • Audiometer malfunction

131
OSHA Occupational Noise Exposure Standard
  • 29 CFR 1910.95
  • Requirements for maintaining and calibrating
    audiometric equipment and technician training
  • Table G-16A of Appendix A
  • Relates A-weighted sound level to allowed
    duration
  • Table A-1 of Appendix A
  • Converts Noise Exposure (Dose) to 8-hour TWA

132
Quantifying Hearing Loss
  • Watch for changes in the HTL (Hearing Threshold
    Level)
  • STS (Standard Threshold Shift) decrease of 10
    db or more at 2000, 3000, or 4000 in either ear
  • Represents permanent hearing loss
  • Call for a re-test (after at least 14 hours of
    relative quiet)
  • TST (Temporary Threshold Shift) a shift in HTL
    that disappears after the person has been in a
    quiet environment for a few hours

133
Standard Threshold Shift (STS)
  • If an STS is identified
  • Notify the employee in writing
  • Provide additional training
  • Provide adequate hearing protection
  • Workers Compensation
  • Realize that WC laws for identifying and
    compensating STS will vary across the states

134
29 CFR 1910.95
  • Enacted in 1971
  • Hearing Conservation Program is required whenever
    employee exposures exceed 85 dBA 8-hr TWA
  • This is half the allowable noise exposure for an
    8 hour day or 50 Daily Noise Dose (DND)
  • Note 90 dBA for an 8-hr TWA is 100 DND

135
Hearing Conservation Program Elements
  • Exposure monitoring
  • Audiometric testing
  • Hearing protective devices
  • Training program
  • Access to the written standard
  • Recordkeeping

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Measuring Occupational Noise
  • Sound Level Meters (SLM)
  • Used for area surveys
  • Settings for average, peak, impulse, ABC scales
  • Noise Dosimeters
  • Used for individual monitoring
  • Clip microphone near the ear
  • Wear all day
  • Calibrate before and after

137
Adding Decibels
  • Often there is a need to combine two or more
    noise sources
  • Because decibels are logarithms, they cannot be
    added directly
  • 80 dB 85 dB ? 165 dB
  • 80 dB 85 db 86 dB

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Example
  • Given three machines in a room measured at 80,
    85, and 87 dB, respectively
  • SPLtotal 10 log (1080/101085/101087/10)
  • SPLtotal 89.6 dB

139
Computing Daily Noise Doseand Calculating 8-hr
TWAs
  • OSHA limits workers to 100 of the daily dose or
    90 dBA for 8-hr TWA
  • D 100 (C1/T1 C2/T2 Cn/Tn)
  • D daily nose dose, in percent
  • C total time of exposure at the measured noise
    level
  • T reference allowed duration for that noise
    level from Table G-16a of Appendix A of 29 CFR
    1910.95

140
Example
  • A workers exposure was monitored for 2 hrs at 80
    dBA, 2 hr at 85 dBA, and 4 hr at 87 dBA. What is
    the DND (Daily Noise Dose)?
  • D 100 (2/32 2/16 4/12.1) 51.8
  • The worker received 51.8 of their DND. (This is
    OK.)
  • Given a DND 51.8, find the 8-hr TWA.
  • Go to Table A-1. Round to 55 (conservative).
    Yields 85.7 dB TWA. The Hearing Conservation
    Program is required.

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Controlling Noise
  1. Engineering Controls
  2. Administrative Controls
  3. PPE

142
Engineering Controls
  • You can make a career out of engineering
    controls for controlling noise
  • Devices insulative curtains coverings for
    noise-reflective floors, ceilings, walls
    vibration isolation devices
  • Remember sound is a wave and cannot turn around
    corners this is the concept of directivity
  • Reflection sound waves can bounce back and
    add sound pressure at the source
  • Resonance a material vibrates at the same
    frequency as the emitted sound use an
    vibration isolator or rubber mounting

143
Engineering Controls
  • Some surfaces absorb the sound energy, or do
    not allow it to reflect effectively
  • Noise control curtains fiber-filled cloth office
    partitions
  • Proper preventative maintenance (PM) on
    machines parts such as motors, bearings, drive
    belts, pumps, etc.
  • Adjustments, lubrication, replacement, vibration
    isolators
  • Think outside the box for new designs and work
    with suppliers
  • One of the best engineering controls is
    distance
  • The relationship between noise and distance
    follows the inverse square law
  • Doubling the distance reduces the noise by ¼
  • Tripling the distance reduces the noise by 1/9

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Administrative Controls
  • Used when engineering controls are exhausted or
    infeasible
  • Limiting time in exposed areas worker rotation
    limiting the number of workers in exposed areas
    (limited access)

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Hearing Protective Devices (HPD)
  • After engineering and administrative controls are
    exhausted and infeasible
  • All workers exposed at 85 dBA for 8-hr TWA must
    be provided HPD at no cost
  • Employers must ensure workers actually wear the
    HPD
  • Employers must provide a variety of HPD

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HPD Continued
  • Employers must train workers to use HPD and how
    to care for them
  • HPD attenuation must effectively reduce noise
    exposure to below the OSHA action level (85 dBA)
  • Noise Reduction Rating (NRR)
  • Typically 22 30 dB NRR
  • Numerical attenuation value determined in a
    laboratory
  • When using the A-Scale, you must deduct 7 dB from
    the NRR
  • When using the C-Scale, no deduction is necessary

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Example
  • Worker is exposed to 98 dBA for 8-hr TWA.
    Earplugs are available with a 29 NRR and earmuffs
    are available with a 25 NRR.
  • Since A-Scale, Earplugs (NRR 29-7 22) and
    Earmuffs (NRR 25-7 18)
  • Earplugs 98 22 76 dBA
  • Earmuffs 98 18 80 dBA
  • Both are below the 85 dBA 8-hr TWA Action Limit

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Extreme Exposures
  • For extreme exposures with 8-hr TWA in excess of
    100 dBA, it may be necessary to use both earplugs
    and earmuffs
  • Their NRRs are not additive
  • Tests show an additional 3 10 dB NRR is
    achieved with the second device

150
References
  • Nims DK. Basics of Industrial Hygiene. John
    Wiley Sons, Inc., 1999. ISBN 0471-29983-9

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HW14
  • Exercises Study Questions
  • P. 195, 1-39, divisible by 5
  • Research Exercises/Stds Questions
  • P. 199, 40-46, pick one
  • Exercises Study Questions
  • P. 224, 1-27, divisible by 5
  • Research Exercises/Stds Questions
  • P. 227, 28-33, pick one
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