Scientific Foundations of Occupational and Environmental Health Nursing Practice

1. Scientific Foundations of Occupational and Environmental Health Nursing Practice By Dr. Ali Saleh

2. Epidemiology • Epidemiology: is the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems. • Incidence rate: the occurrence of new disease or injury per unit of time among persons at risk. • New cases of disease during given time/everyone at risk of developing the disease during that period • Prevalence: the proportion of the population with the condition at a given point in time or during a given time period • New and existing cases/ all who are at risk of developing the disease including those who have it.

3. Epidemiology and Occupational and Environmental Health Nursing • A tool for recognizing, identifying, and preventing hazardous exposures. • Epidemiologic studies are often reported in the OEH literature. • Epidemiologic studies help OEH nurses provide high quality health services.

4. Comparisons of Rates • Relative risk: a measure of the relationship between two incidence rates, that of the exposed and that of the unexposed population. • Attributable risk: a measure of the difference between two rates, one for the exposed and one for the unexposed populations.

5. Types of Rates • Crude rates: based on actual number of events for a given time period but do not reflect true differences in risk among subgroups in the population. • Characteristics-specific rates: allow to compare rates for similar subgroups of two or more populations e.g. age • Adjusted (standardized) rate: taking into consideration the distribution of important characteristics that may affect risk.

6. Epidemiology Screening: is the practice of testing people who are as yet asymptomatic. (for prevention) • Sensitivity: ability of a test to identify correctly those who have the disease. • Specificity: ability of a test to identify correctly those who do not have the disease. • Predictive value: ability to predict disease status from test results • Positive PV: likelihood that individual with a positive test truly has the disease • Negative PV: likelihood that individual with a negative test does not have the disease • ↑ prevalence of disease→ ↑ positive PV • ↑ prevalence of disease → ↓ negative PV

7. Toxicology • Is the study of the adverse effects of chemicals on biologic systems • A chemical is toxic (can cause harm) if all of the following five conditions are met: • Its prosperities make it capable of producing harm. • It is present in sufficient amount. • It is present for sufficient time. • it is delivered by an exposure route that allows it to be absorbed. • It reaches the target body organ/s.

8. Toxicology • Toxic agents can be classified: • Asphyxiants:↓ tissue O2 • Corrosives: irreversible tissue death • Irritants: temporary, but sometimes severe, inflammation of eye, skin, or respiratory tract. • Sensitizers: allergic reactions after repeated exposure. • Carcinogens: capable of causing cancer. • Mutagens: changes to the genetic material of cells that can be passed on to future generations. • Teratogens: malformations in an unborn child • Toxins: have more than one form of action and may act at more than one site.

9. Assessing ch.ch. of Exposure: 1. The dose of an agent: the amount reaches the target organ. • Impossible to be determined accurately • Measuring the amount administered or exposed amount in the environment. • Measuring biomarkers in body tissues. • Vapor or gas: usually as parts per million (ppm) • Solids (dusts or fumes): weight per volume of air e.g. milligrams per cubic meter (mg/m3) • ↑ concentrations→ ↑ absorbed amount • Longer or more frequent periods→ ↑ absorbed amount

10. Assessing ch.ch. of Exposure 2. Acute and chronic exposure • Acute: exposure is short-term and absorption is fairly rapid. (higher level) • Chronic: longer duration or repeated periods of contact (lower level). 3. Guidelines and standards that evaluate seriousness of exposure • e.g. threshold limit values, permissible exposure limits • Published limits cannot be viewed as “safe” levels because of lack of scientific data, lack of agreement, and yet may affect susceptible subgroups.

11. Major Exposure Routes 1. Inhalation • Most common • Most absorption occur in alveoli, gas or a particulate ranging from 1-10 microns in diameter. • Influenced by rate and depth of respirations.(↑ absorbed substance in heavey physical labor). • Target organ could be the lung or could have systematic effect.

12. Major Exposure Routes 2. Cutaneous • Substances enter through: • Epidermal layer • Hair follicles • Trauma or injection • Gases penetrate most freely, liquids less freely, and solids that are insoluble in water or fats do not penetrate the skin.

13. Cutaneous • Greater absorption with: • longer contact • Damage of epidermal cells • Clothing or gloves can trap substances and lead to longer exposure periods.

14. Major Exposure Routes 3. Ingestion • Least common • Ingested chemicals: • Can have a direct adverse effect on the gastrointestinal tract. • Act systemically following their absorption. • Smoking or eating at work can lead to consumption of toxins by contaminated hands, food or smoking materials.

15. Dose – Response Relationship • Lethal dose, 50% (LD50): the dose that produces death in 50% of experimental animals. • lethal concentration, 50% (LC50): the concentration that produces death in 50% of experimental animals. • LD50 and LC50 are examples of terms to describe toxicity.

16. Nature of Effects • Effects of toxins with long latency periods may appear after years of exposure. • Synergistic effects: effects caused by exposure to more than one toxin that surpass the sum of the separate effects of those toxins. • Antagonism: between toxins results in an overall effect that is less than the sum of their separate effects. • Potentiation: a chemical has no adverse effect on its own, but its presence ↑ effect of another substance or make it effective.

17. The Fate of Toxins in the Body • Excretion through: • Air, urine, feces, bile, or perspiration. • Milk, spinal fluid, saliva, and hair. • Most chemicals and their metabolic products are excreted through kidney/urine pathway. • Transformation: process that results in a substance being changed in some way. • Biotransformation: chemicals may be transformed into substance that can be excreted. • Products are less or more toxic than parent chemical. • Individuals differ in the rate the metabolize substances→ individual susceptibility to a toxin.

18. The Fate of Toxins in the Body Excretion of Substances • Some of substances are deposited in body tissue and slowly released and excreted over time. • Half-life: the time it takes for one half of the total absorbed amount to be eliminated from the body. • Length of half-life depends on the agent and the tissue in which it is stored.

19. Endogenous & Exogenous Host Factors Endogenous Factors • Gender: e.g. women have ↑ body fat and may accumulate more lipid-soluble toxins than men. • Genetic differences • Aging • ↑ toxic responses among older adults and children. • Pregnant women • Health conditions

20. Endogenous & Exogenous Host Factors Exogenous Factors • Nutrition factors e.g. deficiencies • Obesity • Lifestyle factors e.g. smoking, alcohol • Stress • Temporary and manageable health conditions.

21. Industrial Hygiene • The anticipation, recognition, evaluation, and control of environmental factors or stresses arising in or from the workplace, which can cause injury, sickness, impaired health and well-being, or significant discomfort among workers or among citizens. • Based on knowledge from many disciplines e.g. engineering, physics, chemistry, and biology.

22. Ergonomics • Ergonomics (human factors): the study of the interaction between humans and their work. • Ergos = work, nomos = laws (in Greek). • It is multidisciplinary field involving health professionals, engineers, behavioral scientists, physiologists, and others. • Its purpose is to • Prevent acute and chronic injuries • Make work sites comfortable • Enhance productivity • Reduce fatigue and errors • Promote job satisfaction

23. Ergonomics • Proper job design → jobs appropriate for workers of both sexes and all ages • Considerations are given to size, strength, visual capacity, hearing capabilities, and limitations. • Fit the job to the person rather than the person to the job.

24. Work-Related Musculoskeletal Disorders • Affected tissues include muscles, tendons, ligaments, peripheral nerves, blood vessels, joints, cartilage, and bones. • Risk factors: • Repetition • Force • Combination of repetition and force (e.g. carpal tunnel syndrom) • Mechanical stress (direct contact with work surfaces or tools) • Compressive forces (e.g. striking objects). • Awkward postures • Vibrations and whole body vibrations • Low temperatures

25. Work-Related Musculoskeletal Disorders Awkward postures 1. Cervical spine injury • Caused by extreme neck flexion and twisting 2. Back injury: caused by • Twisting at the waist • Lifting with legs straight • Bending and reaching repetitively • Maintaining awkward postures for long periods • Carrying, pulling, pushing, or lifting heavy objects from below the knee or above the shoulders • Lifting weight beyond one’s capabilities

26. Work-Related Musculoskeletal Disorders 3. Shoulder injury • Raising the arm or elbow above midtorso without support, reaching behind one’s body 4. Forearm/elbow injury • Repeated rotations (supination and pronation) 5. Wrist/hand injury • Repeated wrist flexion and extension, holding the hand in ulnar deviation

27. High-Risk Jobs of Ergonomic Exposures 1. Office work (equipment and work environment) • Awkward positions (e.g. using computers) • Office environment hazards e.g. poor lighting, obstructions in in walkways, slippery floors, and heavy objects.

28. High-Risk Jobs of Ergonomic Exposures 2. Manual materials handling • E.g. loading trucks, moving heavy goods • Repeated bending, lifting, twisting, and sometimes exposure to vibrations • High risk of back injury

29. High-Risk Jobs of Ergonomic Exposures 3. Assembly work • Repetitive motions • Static or awkward postures, or with poorly designed tools

30. Ergonomics Evaluating risk factors 1. Interviews or questionnaires • Workers have the most complete view of their tasks • Variability, incomplete, or biased 2. Observation and use of checklist • Less variability, fairly efficient (one observer evaluate many workers) • Workers under observations may change their behaviors • Limited time (some risks may be missed) • Observer must be trained.

31. Ergonomics 3. Videotaping and analysis • Does not rely on one person’s assessment • Tape can be repeated, slowed, or frozen • Measurement of time and motion can be highly accurate • Requires expensive equipments and experienced personnel • Behaviors may change during taping • Only a small window of worker’s time is recorded (not for highly variable tasks)

32. Ergonomics Improvements • General environment: provide adequate illumination, comfortable levels of temperature and humidity, good visibility of labels and signs, and clear, audible auditory signals. • Workstations and chairs: should be adjustable to accommodate workers of different sizes. • Layout: place tools, controls, and materials in front of the worker to prevent twisting, reaching, and bending; and keep work place free of obstacles. • Postures: avoid static postures, locate and orient work to promote neutral positions.

33. Ergonomics Improvements • Repetition: engineer to reduce repetition, vary tasks, rotate workers to different jobs, allow rest time. • Forces: reduce the size and weight of objects held, use power grips rather than pinch grips, balance tools, provide correctly fitting gloves, and sharpen tools often. • Mechanical stresses: ensure that handles on equipment fit the worker’s hands, pad or eliminate sharp edges. • Vibration: eliminate vibrating tools if possible, isolate sources of vibration, keep tools and equipments properly maintained, maintain even floor surfaces to reduce vibration from driving, reduce driving speeds of vehicles.

34. Ergonomics Improvements • Lifting: reduce size and weight of tools and objects that are lifted, use mechanic lifting devices, use gravity to move work, raise the work (or lower the operator), provide grips and handles, reduce friction where objects are slid from one point to another, increase friction when objects are held. • Work organization: staff adequately, alternate physically demanding and mentally demanding tasks vary the rate and nature of tasks as much as possible, provide more frequent short breaks (better than less frequent long breaks).

35. Injury Epidemiology • Occupational injury epidemiology: the study of the natural history of injuries helps to define the host, agent, vector, and environmental (psychosocial and physical) factors that contribute to injury. • Ch. Ch.s of occupational injury: • Occup. Injuries are not random events • Injuries are predictable and preventable • Injuries result when energy is exchanged in a manner and does sufficient to overcome the host’s threshold of resistance in the presence or absence of certain environmental conditions.

36. Injury Epidemiology Sources of injuries • Mechanic or kinetic energy • Thermal energy • Electric energy • Radiation • Chemical energy • Absence of energy-producing mechanisms necessary to sustain life e.g. absence of respiration.

37. Countermeasures Pre-event Countermeasures • Preventing the creation of hazard • Reducing the severity of hazard • Preventing the release of hazard • Modifying the rate of release of hazard • Separating the hazard from the individual

38. Countermeasures Event Countermeasures • Placing a physical barrier between hazard and person • Modifying the basic qualities of the hazard • Increasing the individual’s resistance to injury Post-event Countermeasures • Evaluate injury rapidly, prevent continuation of injury, and mitigate the extension of its effects • Provide medical and surgical care and rehabilitative and reconstructive care.

39. Social and Behavioral Sciences • The leading causes of death have shifted from infectious diseases to chronic diseases, often related to behaviors and environmental factors. Behavioral Sciences • The behavior of individuals and groups is complex: • People often make choices that they know are not good for their health. • The key of behavioral change is understanding the human thought processes that affect behavior. • Focusing of behavioral strategies to improve healthy behaviors. • Behavioral research → understanding of neurologic and behavioral effects of certain exposures.

40. Behavioral Sciences • Behavioral theories and models: • Explain why people behave as they do. • Provide a source of ideas to understand behavior. • Help to develop more effective interventions.

41. Social and Behavioral Sciences Social Sciences • The relationship of social phenomena to health and illness outcomes • Social indices that may affect occupational health include: rates of violence, divorce, unemployment or holding multiple jobs. • Complete understanding of nature of work and the social context of the workplace.

42. Social and Behavioral Sciences Health Promotion and Risk Reduction • Organizational “healthy policy” • Improve healthy behaviors • Health promoting and health damaging policies are likely to receive increased scrutiny in the coming years. • Organizational change is a critical factor in achieving a healthy occupational environment.