UNIT 2

INDUSTRIAL TOXICOLOGY AND HUMAN ANATOMY

HPEO 408 Occupational Health Hazards

TOXICOLOGY TERMINOLOGY REVIEW

Toxicity – the degree a substance can harm humans, animals, or environment

Hazard – is something that has the potential to cause harm if exposed to a certain set of circumstances

Risk – is the probability that harm (i.e. adverse effect) will occur given exposure

TOXICITY VS. HAZARD

Characteristics of hazard: Route of exposure Form Dose/concentration Absorption rate Exposure duration Surface area exposed Area exposed (ex. skin thickness)

How hazard reacts within the body Distribution Metabolism Excretion Other exposures (i.e. mixtures)

FACTORS AFFECTING TOXICITY AND RISK

1. Independent effects Occurs when the hazards are different in composition and act in a different manner and

on different organ systems

2. Additive effects The total effect is the sum of each independent effect Occurs when the hazards act in a similar way and produce the same effect Example: Chlorinated insecticides and halogenated solvents liver toxicity.  

Potentiated effects When a substance causes an increase in harm that on its own does not elicit an effect Example: CO potentiates noise induced hearing loss from exposure to noise

1. Synergistic effects Is an interaction where one hazard exacerbates the adverse effect of another. Example: asbestos exposure and smoking lung cancer

Antagonistic effects The effect of one substance cancels or reduce the effect of another Often related to enzyme function and metabolism Example: ethanol reduces effects of methanol exposure

MULTIPLE EXPOSURES

How do we adjust for these when determining compliance or health risk?

1. Independent effects Use TLVs as normal

2. Additive effects Calculate TWA for mixtures (located in your text book)

§ Antagonistic effects Use TLVs as normal Has reduced effects but don’t know to what level so take conservative

approach

§ Potentiated/ synergistic effects1.There is no clear method2.Indicates we must take extreme caution!

MULTIPLE EXPOSURES II

TLV designation

Indicates that skin exposure may be a significant contributor to overall dose

Determined by: Studies showing significant absorption through skin or systemic

effects Low dermal LD50 values with animal studies

NOTE: TLVs/exposure limits are developed without considering skin exposure

What does this mean for the OH professional? Systemic effects may occur due to dermal exposure over inhalation Identifies need for PPE or other controls to limit skin exposure Biological monitoring would be appropriate to monitor exposure

SKIN NOTATION

Odor or mild irritation detectable BELOW levels that are hazardous

Largely based on comparison of TLV to published odor thresholds

If using odor thresholds should preform odor threshold tests on each worker

Not good to use when: Odor threshold is over TLV Odor threshold is very low (i.e. well below action limit) Olfactory fatigue it common Worker is unable to detect odor

WARNING PROPERTIES

Considerations using odor thresholds: Differences in odor thresholds across populations

Effects of aging (decrease smell ability with age)

Olfactory system can become fatigued (loose its sense of smell)

Number of conditions that can result in olfactory dysfunction rhinitis, sinusitis, polyps, Inflammation and/or trauma to head exposure to some chemicals (ex. metallics)

WARNING PROPERTIES II

NOAEL No Observed Adverse

Effect Level

Highest data point where there was no effect

LOAEL Lowest Observed

Adverse Effect Level

Lowest data point where there was an effect

NOAEL/LOEAL

Immediate vs. delayed effects

Reversible vs. irreversible

Local vs. systemic “Local” - site of action of the agent is at the point of contact

Absorption does not necessarily occur “Systemic” - site of action other than the point of contact

Absorption has taken place

TOXIC EFFECTS CONSIDERATIONS

ANATOMY INTRODUCTION

Network of cells responsible for communication

Contains high fat content fat-soluble agents of concern and are more likely able to pass the blood-brain barrier

Broken into two categories:

The central nervous system (CNS) includes the brain and spinal cord

The peripheral nervous system Includes the nervous structures (motor and sensory nerves) that do not

lie in the CNS

NERVOUS SYSTEM

Set of glands responsible for hormone production and regulation of the body using feedback systems

Includes hypothalamus, adrenal, pituitary, pineal, and thyroid glands

Most common/important regulation roles include regulation of:

Metabolism

Growth

Development

Reproductive cycles

Mood

ENDOCRINE SYSTEM

Responsible for distributing blood/lymph in the body

Caries substances throughout the body and to and from cells nutrients, gases, hormones, enzymes, and waste

Stabilizes body temperature and pH, and fights diseases

Broken into two categories: The cardiovascular system

Includes the heart, blood, and blood vessels

The lymphatic system Includes the thymus, spleen, bone marrow, and lymphatic tissue

CIRCULATORY SYSTEM

Primary function is to process/metabolize nutrients from the blood Also metabolizes other substances Considered the body’s detoxifier; therefore, susceptible to toxins Liver cells can regenerate after toxic damage, but

prolonged/repeated exposure can lead to permanent liver damage

Liver detoxification process can: Metabolize toxins into safe forms or metabolites Metabolize toxins into more toxic metabolites

Methanol formaldehyde formic acid Metabolized by (1) alcohol and (2) aldehyde dehydrogenase enzymes

LIVER

Includes kidneys, bladder, ureters, urethra, and sphincter muscles

Responsible for producing, filtering, storing, and excreting urine

Primary function is to excrete unwanted waste products including toxins

Toxins typically have to be water soluble before they are excreted

Non-water soluble toxins can be modified by liver to allow for excretion

Kidneys – maintain fluid and electrolyte balance by filtration and selective re-absorption into the blood

URINARY SYSTEM

HAZARD IDENTIFICATION

EXAMPLES

A hazard is the actual chemical/biological/physical agent that may cause harm if exposed. This is what you are being asked to provide in questions asking you to identify the

hazards involved with a job, task, or industry.  Examples: detergents, dust, bacteria, non-ionizing radiation, vibration

A health outcome/effect is the outcome that may occur due to exposure to the hazard.  Examples: skin irritation, cancer, breathing difficulties, burns, hearing loss,

amputations 

A source of exposure (or exposure source) is the vehicle or process the exposure is originating from. Examples: cleaning, grinding, smelting, mixing, blood, feces/sewage

A route of exposure is the manner in which people are exposed to the agent, or the way the hazard enters the body.  Examples: inhalation, skin contact/absorption, ingestion, injection

HAZARD TERMINOLOGY REVIEW

To clarify, when asked to provide the hazards, we want the actual agent that causes the harm (i.e. the chemical, biological, or physical agent)

Often students can get confused and provide health effects or sources of exposures loss of marks on assignments/quizzes

Sometimes this can be tricky, especially with physical hazards

Correct answers will properly identify the hazard however, the best answer is to identify the hazard and include additional information such as the outcome, source/route of exposure to explain the hazard

The next slide outlines examples of this where: The first row will name the hazard The second row will name the hazard and supplement it with explanatory

information

HAZARD IDENTIFICATION

Vibration exposure Whole body vibration from driving forklifts

Noise exposure Hearing loss could occur due to exposure to noise from the operating equipment

Temperature extremes Risk of heat stress occurring due to high/elevated temperatures.

Wood dust Inhalation of wood dust from sawing operations

Welding fumes Metal fume fever due to inhalation of welding fumes

Mold Inhalation of fungal spores from water damaged ceiling tiles

Hepatitis C virus Risk of contracting Hepatitis C from exposure to contaminated blood through a needle

stick injury.

HAZARD TERMINOLOGY EXAMPLES