Nature of Environmental Health Hazards

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

2. 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

3.  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

4. 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

5. 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

6. 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 hazards e.g. stress, lifestyle disruption, workplace discrimination, effects of social change, marginalization, unemployment

7. Types of EH Hazards (cont’d) Classified according to: • nature • natural vs anthropogenic • traditional vs modern • route of exposure • setting

8. 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

9. Biological, chemical & physical hazards by routes of exposure

10. BIOLOGICAL HAZARDS Include 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

11. 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

12. 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

13. 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

14. 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

15. 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

17. Growth of biological agents are slowed down or stopped by: • defense mechanisms of the body • drugs

18. 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)

19. 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)

20. Route of exposures Source: • 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

21. Air, water, dirt, etc Air Food, water, drugs Exposure Media inhalation exhalation ingestion Major uptake pathways Skin Respiratory tract GI-tract bile exfoliation Blood Transport & distribution Other organs Liver Kidney Major excretory pathways Sweat Hair Urine Faeces external contamination

22. 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

23. O OH Gluc Bioactivation of Benzene Phase II Phase I Phenylglucuronide (hydrophilic; easily excreted) Benzene (the original chemical) Benzene epoxide (a dangerously toxic product) Phenol (an intermediate that the body can handle)

24. xenobiotics highly lipophilic metabolically stable lipophilic polar hydrophilic accumulation in body fat phase I (bioactivation or inactivation) oxidation, reduction, hydrolysis polar phase II (bioinactivation) conjugation hydrophilic extracellular mobilization plasma circulation biliary excretion renal excretion secretion

25. Toxicityany harmful effect of a chemical or a drug on a target organ • Systemic toxicity • Liver toxicity • Kidney toxicity • Skin toxicity • Neurotoxicity • Immunotoxicity

26. Alteration of genetic • codes & information: • gene mutation • chromosomal alteration • gene rearrangements Biological agents Chemical agents DNA Physical agents • 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, recreating • the original structures. Repair can be faulty, leading to heritable changes • Chromosomal alterations • via 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 causes • might be translocations or inversions of large parts of chromosomes Multistage process of carcinogenesis: Initiation Promotion Progression

27. 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 compounds ED50 : dose that would cause the effect in half of the test population LD50 : 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 tests animals 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 testing performed by exposing animals to the chemical being tested for the whole of the animal’s lifetime • Reproductive studies on parents & offspring

28. Toxicity Testing (cont’d) • Genotoxic short-term tests short-term tests for gene mutation & chromosome alterations both in vitro & in vivo • Human studies clinical or epidemiological studies • Structure-activity relationships Right-to-know legislation  hazard identification & control

29. 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

30. 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

31. 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

32. Other physical hazards:vibration, radiation, light, lasers, pressure, temperatures What are potential health effects of such hazards?

33. 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

34. The Haddon Matrix

35. 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

36. Thank you…