Nature of Environmental Health Hazards Didi Supardi, dr. Dept. of Public Health & Preventive Medicine.

Nature of Environmental Health

Hazards

Didi Supardi, dr.

Dept. of Public Health & Preventive Medicine

OBJECTIVE:• To describe the difference between hazard & risk• To explain the logic of the various methods of classifying

environmental hazards• To describe a scheme for identifying the level of hazard &

toxicity• To explain why knowledge of the toxicology,

microbiology, or physical properties of an environmental hazard is essential to determining the most appropriate approach to its risk assessment

• To identify different experimental investigative methods• To explain the biological significance of bio-

transformation process• To list the basic characteristics of chemical, physical,

biological, mechanical, & psychosocial hazards

Required Reading

Yassi A, Kjellström T, de Kok T, Guidotti TL. Basic Environmental Health. Chapter 2: Nature of Environmental Health Hazards. New York: Oxford University Press, 2001

Definition

Hazard a factor or exposure that may adversely affect

health (Last, 1995)

a source of danger a qualitative term expressing the potential of an

environmental agent to harm the health of certain individuals if the exposure level is high enough &/or if other conditions apply

Definition (cont’d)

Risk the probability that an event will occur, e.g. that

an individual will become ill or die within a stated period of time or before a given age; the probability of a (generally) unfavorable outcome (Last, 1995)

the quantitative probability that a health effect will occur after an individual has been exposed to a specified amount of a hazard

Types of EH Hazards Biological hazards

e.g. bacteria, viruses, parasites Chemical hazards

e.g. toxic metals, air pollutants, solvents, pesticides Physical hazards

e.g. radiation, temperature, noise Mechanical hazards

e.g. motor vehicle, sports, home, agriculture, & workplace injury hazards

Psychosocial hazardse.g. stress, lifestyle disruption, workplace

discrimination, effects of social change, marginalization, unemployment

Classified according to: nature natural vs anthropogenic traditional vs modern route of exposure setting

Types of EH Hazards (cont’d)

Traditional Hazards• Disease vectors• Infectious agents• Inadequate housing

& shelter• Poor-quality drinking

water & sanitation• Indoor air pollution

from cooking• Dietary deficiencies• Hazards of child birth• Wildlife & domestic

animals• Injury hazards in

agriculture

Modern Hazards• Tobacco smoking• Transport hazards• Pollution from

sewage & industry• Outdoor air

pollution from industry & motorcars

• Overuse or misuse of chemicals

• Industrial machinery

• Unbalanced diet

Biological, chemical & physical hazards by routes of exposure

Biological Chemical Physical

AIR

Agent/source Microorganisms Fumes, dust, particles Radiation, heat, noise

Vectorial factors Coughing, exhalations Contaminated air Climate, unguarded exposures

Routes Inhalation, contact Inhalation, contact Inhalation, direct penetration

WATER

Agent/source Microorganisms, decayed organic material

Discharges, teaching, dumping

Radiation, heat in power station cooling water

Vectorial factors Insects, rodents, snails, animal excreta, food chain

Contaminated food & water

Accidents, contaminated food & water

Routes Bites, ingestion, contact Ingestion, contact Ingestion, contact

BIOLOGICAL HAZARDSInclude all of the forms of life (as well as the

nonliving products they produce) plants, insects, rodents, other animals, fungi, bacterial,

viruses, protozoa, a wide variety of toxins & allergens; & prion

Routes of exposure:• Air• Water• Food• Direct penetration• Biting

Person exposed the agent distributed via blood, lymph, or other body fluids to the parts of the body most favorable for it to grow

Prions (proteinaceous infectious particles)• Infectious agents (not organisms) made of protein (yet to be fully

characterized)• Multiply by converting normal protein molecules into dangerous

ones by changing their shapes• Responsible for the various forms of spongiform

encephalopathy, e.g.: - bovine spongiform encephalopathy (BSE) or ‘mad-cow’ disease) - Creutzfeldt-Jakob disease (CJD) - kuru (transmitted by ritual handling of bodies & brains of the dead)

• Symptoms of the human prion diseases: dementia, loss of coordination

Viruses• a piece of nucleic acid (either DNA or RNA), which makes

its progeny by orchestrating the production of virus particles by a cell

• viruses that lack a lipoprotein envelope (e.g. hepatitis A, gastroenteritis viruses) can grow in the human gut & be spread by food & water

• viruses with a lipoprotein envelope have limited survival outside a host & so are spread in aerosols or inoculations of body fluids from person to person (e.g. measles)

• reproduces only inside a host cell• viral diseases do not respond to antibiotics, but some

respond to specific antivirals

Bacteria• most have sufficient energy supply to reproduce outside a

cell• have genetic material but no nucleus• divide by splitting in half• exist singly or in short chains of two or more• classified by shape, oxygen requirement & ability to take

up a special stain

Fungi• simple plant plant organisms that lack the chlorophyll

needed to use carbon dioxide & sunlight to build sugars & structural molecules

• classified into yeast (single-celled) or moulds, which grow as branching filaments called hyphae

• yeast reproduce by budding, moulds by branching & longitudinal growth of hyphae, as well as by producing sexual spores

Protozoa• the simplest class of animal & consisting of a single

nucleated cell• each cells has organelles that carry on such functions as

locomotion, nutrition, excretion, respiration• e.g. : plasmodium, cryptosporidium, giardia

Arthropods• the large phylum of animal life that includes insects,

spiders, mites & ticks (as well as crabs & lobsters)• some of these creatures bite, sting, cause allergic

reactions, and may serve as vectors for viruses & other infectious agents

Pathway DiseaseInadequate sanitation, the dumping of untreated sewage into surface water, poor hygienic practices water polluted by human excreta

cholera, typhoid fever, dysentry, other diarrheal diseases, hepatitis A, schistosomiasis

Overcrowding, poorly ventilated housing airborne transmission

tuberculosis, measles, influenza, pneumonia, pertussis, cerebrospinal meningitis

Unhygienic animal husbandry zoonoses transmission

plague & hydatids diseases

Stagnant waters, unsanitary housing, refuse dumping vector-borne transmission

malaria, trachoma, schistosomiasis, filariasis, yellow fever, plague, typhus, trypanosomiasis

Growth of biological agents are slowed down or stopped by:

• defense mechanisms of the body

• drugs

CHEMICAL HAZARDS

Inorganic Substances- halogens (e.g. fluorine, chlorine, bromine, iodine)

- alkaline compounds (e.g. NH3, Ca(OH)2, KOH, NaOH

- ozone (O3)

- NOx and SOx

- metals (e.g. cadmium, chromium, copper, lead, manganese, mercury, nickel, arsenic)

Organic Compounds- aliphatic hydrocarbons (e.g. methane, ethane, propane,

butane, pentane, hexane, heptane, octane)

- alicyclic hydrocarbons (e.g. cyclohexane, methylcyclohexane, turpentine)

- aromatic hydrocarbons (e.g. benzene, toluene, styrene, naphthalene)

- halogenated hydrocarbons (e.g. chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethyene, polyviyl chloride)

- alcohols (e.g. methanol, ethanol, propanol)

Route of exposuresSource:• natural events• man-made: industrial, agricultural, commercial,

domestic, manufacturing wastes

Exposure:- inhalation - breastfeeding

- oral ingestion - placental transfer

- absorption via the skin - inoculation & direct penetration

- absorption via the eyes

Air, water,dirt, etc

Food, water,drugsAir

Skin Respiratorytract GI-tract

BloodOtherorgans Liver

Kidney

Sweat Hair Urine Faeces

bileexfoliation

inhalation exhalation ingestion

external contamination

ExposureMedia

Major uptakepathways

Transport &distribution

Majorexcretorypathways

Biotransformation

Hydrophobic or lipophilic hydrophilic

Phase I : - the molecule is altered by the introduction of electrostatically charged (polar) groups

- result of oxidation, reduction, or hydrolysis

Phase II: substances are combined w/ hydrophilic endogenous compounds

Bioactivation of Benzene

O

OH Gluc

Benzene(the original chemical)

Benzene epoxide(a dangerously toxic

product)

Phenol(an intermediate thatthe body can handle)

Phenylglucuronide(hydrophilic; easily

excreted)

Phase I Phase II

xenobiotics

biliary excretion

extracellular mobilization

plasma circulation

renal excretion secretion

phase II(bioinactivation) conjugation

phase I(bioactivation or inactivation)

oxidation, reduction, hydrolysis

accumulation in body fat

lipophilic polar hydrophilichighly lipophilic

metabolically stable

polar

hydrophilic

Toxicityany harmful effect of a chemical or a drug on a target organ

• Systemic toxicity

• Liver toxicity

• Kidney toxicity

• Skin toxicity

• Neurotoxicity

• Immunotoxicity

Chemical agents

Biological agents

Physical agents

DNA

Alteration of geneticcodes & information:- gene mutation- chromosomal alteration- gene rearrangements

Multistage process of carcinogenesis:

Initiation Promotion Progression

• Gene mutation:the result of single or multiple base pair changes (substitutions, deletions, insertions)in the DNA. Normally, the cell defense mechanisms can repair DNA damages, recreatingthe original structures. Repair can be faulty, leading to heritable changes

• Chromosomal alterationsvia damage by genotoxic agents, leading to structural aberrations (breaks, deletions, translocations), &via loss or gain of one or more chromosomes & sometimes changes in the number of chromosomes

• Gene rearrangements: characterized by altered gene expression (gene amplification, loss of activity). The underlying causesmight be translocations or inversions of large parts of chromosomes

Toxicity Testing• Acute toxicity studies

to predict human effects of short-term, high-level exposures; can provide a measure of the toxic potential of different compoundsED50 : dose that would cause the effect in half of the test populationLD50 : dose that would kill half of the test population

LC50 : concentration of gas or vapor that kills half the test population

LD50 & LC50 : crude indices of toxicity

• Sub-chronic testsanimals exposed repeatedly to a given chemical over a relatively long period (28 days or longer), normally 10% of the lifetime of the selected animals

• Chronic toxicity testingperformed by exposing animals to the chemical being tested for the whole of the animal’s lifetime

• Reproductive studieson parents & offspring

Toxicity Testing (cont’d)

• Genotoxic short-term testsshort-term tests for gene mutation & chromosome alterations both in vitro & in vivo

• Human studiesclinical or epidemiological studies

• Structure-activity relationships

Right-to-know legislation hazard identification & control

PHYSICAL HAZARDS

Forms of potentially harmful energy in the environment that can result in either immediate or gradually acquired damage when transferred in sufficient quantities to exposed individuals

e.g.: sound waves, radiation, light energy, thermal energy, electrical energy

Noise

• Noise: an unwanted sound• Sound intensity: measured in decibels (dB)• Risk of incurring hearing loss begins w/

prolonged exposure to sound of + 75 dB(A)• Rule of thumb:

if a loud voice is not understandable at a distance of 1 m b/c of excessive background noise, the background noise level is above 85 dB & likely to be dangerous

Hearing conservation program

• Regular monitoring of the workplace• Baseline & annual audiograms (for all exposed

workers)• In-service & pre-service (worker) education• Systematic record keeping• Worker notification• Provision of hearing protection

Other physical hazards:vibration, radiation, light, lasers, pressure, temperatures

What are potential health effects of such hazards?

Mechanical Hazards

those posed by the transfer of mechanical or kinetic energy (the energy of motion)

Injury, trauma, accidents

Vulnerable groups: children, the elderly, & disadvantaged groups

The Haddon Matrix

Factors

Phases Human Vehicle Environment

Pre-injury

InjuryPost-injury

Psychosocial Hazards

Potential sources of work-related psychosocial stress:

- factors intrinsic to the job

- the role of the worker in the organization

- career development

- interpersonal relationships at work

- organizational structure & climate

Thank you…