Thematic Area 6: Occupational Health and Safety (OHS)
Q51. According to the Occupational Safety and Health administration guidelines, which strategy represents the most effective level of control within the “Hierarchy of Controls” framework? A) Administrative Controls (e.g., training, rotating shifts) B) Personal Protective Equipment (PPE) (e.g., respirators, gloves) C) Engineering Controls (e.g., ventilation enclosures) D) Elimination of the hazard at its source
Thank you for reading this post, don't forget to subscribe!Thank you for reading this post, don't forget to subscribe!- Correct Answer: D
- Rationale: The Hierarchy of Controls prioritizes interventions by efficacy: Elimination is most effective, followed by Substitution, Engineering controls, Administrative controls, and lastly, PPE.
Q52. A factory worker operating heavy textile weaving machinery for 8 hours a day is exposed to continuous noise levels of 98 dBA. Without hearing protection, this worker is at high risk of developing: A) Acute infectious otitis media B) Noise-Induced Hearing Loss (NIHL) due to damage to cochlear hair cells C) Sudden rupture of the tympanic membrane D) Presbycusis
- Correct Answer: B
- Rationale: Prolonged exposure to sound levels exceeding the standard 8-hour occupational permissible exposure limit (85 dBA) causes irreversible damage to the outer hair cells of the cochlea, leading to NIHL.
Q53. Agricultural extension workers applying chemical organophosphate insecticides on farms must wear respirators fitted with charcoal filters. What specific hazard route are they protecting? A) Ingestion route B) Inhalation route C) Dermal absorption route D) Injection route
- Correct Answer: B
- Rationale: Charcoal filter respirators trap vaporized chemical droplets and toxic gases during breathing, preventing systemic entry via the pulmonary pathway.
Q54. A construction worker develops chronic shortness of breath and chest pain. An X-ray reveals progressive pulmonary fibrosis caused by chronic inhalation of crystalline silica dust during stone cutting. This occupational lung disease is called: A) Asbestosis B) Byssinosis C) Silicosis D) Anthracosis
- Correct Answer: C
- Rationale: Silicosis is a form of pneumoconiosis caused by inhaling fine respirable particles of crystalline silicon dioxide, which trigger nodular fibrosis in lungs.
Q55. In the context of ergonomics, which risk factor is primary in causing Musculoskeletal Disorders (MSDs) among workers on an electronics assembly line? A) Exposure to ionizing radiation fields B) High ambient room temperatures C) Repetitive hand movements, awkward body postures, and prolonged static loading D) Inhalation of volatile chemical organic solvents
- Correct Answer: C
- Rationale: Ergonomics optimizes the human-machine interface. MSDs are caused by physical tasks involving highly repetitive movements, excessive force, and non-neutral body positioning.
Q56. What type of hazard is represented by blood-borne pathogens (such as Hepatitis B virus and HIV) handled by laboratory technicians during routine diagnostic serum processing? A) Physical hazard B) Biological hazard C) Chemical hazard D) Psychosocial hazard
- Correct Answer: B
- Rationale: Biological hazards include infectious agents, viruses, bacteria, fungi, and parasites present in occupational settings.
Q57. What is the fundamental purpose of a Material Safety Data Sheet (MSDS) or Safety Data Sheet (SDS) provided with industrial chemical products? A) To list the market price and discount rates of the chemical B) To provide comprehensive information on chemical properties, health hazards, safe handling, storage, and emergency first-aid measures C) To advertise the chemical company’s financial achievements D) To outline the legal patent registration codes of the substance
- Correct Answer: B
- Rationale: SDS forms are mandatory hazard communication documents that detail safety profiles, chemical hazards, and mitigation requirements for worker safety.
Q58. A coal miner presents with progressive respiratory impairment. Biopsy confirms “Black Lung Disease,” secondary to accumulation of coal dust in the lungs. What is the technical name for this occupational disease? A) Byssinosis B) Coal Workers’ Pneumoconiosis (CWP) C) Farmer’s lung D) Siderosis
- Correct Answer: B
- Rationale: CWP (anthracosis) results from long-term inhalation of coal mine dust, leading to dust macule formation and progressive massive fibrosis.
Q59. Which occupational group faces the highest exposure risk to “Byssinosis” (brown lung disease), caused by inhaling raw textile dust particles? A) Underground gold miners B) Cotton textile mill factory workers C) Cement manufacturing workers D) Hospital radiology technicians
- Correct Answer: B
- Rationale: Byssinosis is an occupational lung disease primarily affecting workers in the cotton, flax, and hemp processing industries due to raw organic fiber dust inhalation.
Q60. According to international labor standards, what is the maximum permissible weight a healthy adult male worker should lift manually under optimal conditions without mechanical assistance to prevent lower back injuries? A) 10 kg B) 23 kg to 25 kg C) 90 kg D) 150 kg
- Correct Answer: B
- Rationale: NIOSH and international ergonomic guidelines recommend an ideal maximum weight limit (The Lifting Equation) around 23 kg (51 lbs) to mitigate structural lumbar spine strains.
Thematic Area 7: Vector and Rodent Control
Q61. An Environmental Health Officer is planning an Integrated Vector Management (IVM) program to control Malaria in an Ethiopian town. Which mosquito genus must be targeted as the primary biological vector of malaria? A) Aedes B) Culex C) Anopheles D) Mansonia
- Correct Answer: C
- Rationale: Malaria is transmitted exclusively by infected female mosquitoes belonging to the genus Anopheles, particularly Anopheles arabiensis in Ethiopia.
Q62. What is the primary environmental management strategy (source reduction) used to control the breeding of Anopheles mosquito larvae near residential areas? A) Mass distribution of insecticide-treated bed nets B) Draining, filling, or levelling stagnant water pools and clearing shoreline vegetation C) Applying high doses of indoor residual spraying (IRS) with DDT D) Prescribing prophylactic chloroquine medications to all citizens
- Correct Answer: B
- Rationale: Source reduction modifies physical environments to eliminate breeding sites (stagnant water pools), preventing mosquitoes from laying eggs and completing their aquatic life cycle.
Q63. A patient in a lowland region presents with a high fever, severe joint pain, and a distinct macular rash. Diagnostic testing confirms Dengue Fever. Which vector species is responsible for transmitting this virus? A) Anopheles gambiae B) Aedes aegypti C) Glossina morsitans D) Simulium damnosum
- Correct Answer: B
- Rationale: Dengue, Zika, and Chikungunya viruses are primary transmitted to humans by day-biting mosquitoes of the genus Aedes, specifically Aedes aegypti.
Q64. In the control of Rodents (such as Rattus rattus), using chemical rodenticides that are anticoagulants kills rats primarily by causing: A) Acute nervous system paralysis and asphyxiation B) Severe internal hemorrhaging and bleeding due to failure of blood clotting mechanisms C) Total blockage of the upper digestive tract D) Immediate renal failure and dehydration
- Correct Answer: B
- Rationale: Anticoagulant rodenticides (like warfarin or brodifacoum) block the vitamin K cycle, disrupting blood coagulation factors and leading to fatal internal bleeding.
Q65. Which vector-borne disease is transmitted to humans by the bite of infected blackflies (Simulium genus), which breed exclusively in fast-flowing river waters, causing severe skin lesions and blindness? A) Leishmaniasis B) Onchocerciasis (River Blindness) C) African Trypanosomiasis D) Lymphatic Filariasis
- Correct Answer: B
- Rationale: Onchocerciasis is caused by the microfilarial worm Onchocerca volvulus and is transmitted by Simulium blackflies that require highly oxygenated, rapidly flowing water to breed.
Q66. The mechanical transmission of enteric pathogens like Shigella and Salmonella from human feces to uncovered food items in kitchens is most commonly facilitated by which domestic insect vector? A) Bedbugs (Cimex lectularius) B) Houseflies (Musca domestica) C) Body lice (Pediculus humanus) D) Soft ticks (Ornithodoros)
- Correct Answer: B
- Rationale: Houseflies feed on waste and feces, collecting pathogens on their mouthparts, body hairs, and sticky leg pads, which are transferred mechanically when landing on human food.
Q67. Which vector species transmits Visceral Leishmaniasis (Kala-azar), a disease endemic to certain lowlands of Ethiopia? A) Phlebotomine Sandflies B) Tsetse flies C) Deer flies D) Stable flies
- Correct Answer: A
- Rationale: Leishmaniasis is a protozoan disease transmitted by the bite of infected female phlebotomine sandflies.
Q68. What biological vector control method introduces a specific natural predator to eliminate vector populations without chemical pollution? A) Spraying organophosphate chemicals into wetlands B) Introducing larvivorous fish (like Gambusia affinis) into ponds to consume mosquito larvae C) Installing mechanical wire meshes on house windows D) Burning neem leaves inside residential bedrooms
- Correct Answer: B
- Rationale: Biological control employs natural enemies to suppress pests. Larvivorous fish eat mosquito larvae, serving as an effective chemical-free intervention.
Q69. A community in a valley reports an outbreak of African Trypanosomiasis (Sleeping Sickness). Which vector must be targeted to manage this outbreak? A) Blackfly (Simulium) B) Tsetse fly (Glossina genus) C) Sandfly (Phlebotomus) D) Midges (Culicoides)
- Correct Answer: B
- Rationale: Tsetse flies are the biological vectors responsible for transmitting the protozoan parasite Trypanosoma, which causes sleeping sickness in humans and Nagana in livestock.
Q70. What is the fundamental public health reason for controlling infestations of the Norway rat (Rattus norvegicus) in urban grain stores? A) Rats consume excessive oxygen inside the storage facilities B) Rats are reservoirs for the bacterium Yersinia pestis, which is transmitted by oriental rat fleas (Xenopsylla cheopis) to cause the Plague C) Rat fur can be harvested for industrial textile production D) Rats chemically alter the nutritional value of proteins in grains
- Correct Answer: B
- Rationale: Rats maintain the urban reservoir for plague. When rats die, their fleas (Xenopsylla cheopis) leave the host and bite humans, transmitting Yersinia pestis.
Thematic Area 8: Air Quality and Noise Control
Q71. Which air pollutant is classified as a “Secondary Air Pollutant” because it is not emitted directly from sources, but forms in the atmosphere through photochemical reactions in the presence of sunlight? A) Carbon monoxide (CO) B) Sulfur dioxide (SO2) C) Ground-level Ozone (O3) D) Particulate Matter (PM10)
- Correct Answer: C
- Rationale: Secondary pollutants form via chemical reactions among primary pollutants. Ground-level ozone is generated when nitrogen oxides (NOx) and Volatile Organic Compounds (VOCs) react in sunlight.
Q72. In rural Ethiopian households relying on traditional biomass fuels (wood, animal dung) for indoor cooking on open three-stone fires, women and children suffer high exposure to which indoor air pollutant? A) Chlorofluorocarbons (CFCs) B) Carbon monoxide (CO) and Fine Particulate Matter (PM2.5) C) Radon gas D) Asbestos fibers
- Correct Answer: B
- Rationale: Incomplete combustion of biomass fuels in poorly ventilated kitchens generates dangerous concentrations of carbon monoxide and respirable particulate matter, driving respiratory illnesses.
Q73. What is the physiological mechanism by which Carbon Monoxide (CO) exerts its acute toxic effect on the human body? A) It destroys the alveolar walls of lungs causing immediate emphysema B) It binds to hemoglobin with an affinity 200 times higher than oxygen, forming carboxyhemoglobin and causing systemic hypoxia C) It paralyzes the vocal cords and causes asphyxiation D) It suppresses insulin production in the pancreas
- Correct Answer: B
- Rationale: CO competitively binds to hemoglobin sites, shifting the oxygen-hemoglobin dissociation curve and blocking oxygen transport to vital tissues.
Q74. Which particle size of Particulate Matter (PM) poses the greatest health risk to the human lower respiratory system because it can bypass upper airway defenses and penetrate deep into alveoli? A) PM100 (diameter of 100 micrometers) B) PM50 (diameter of 50 micrometers) C) PM2.5 (diameter of 2.5 micrometers or less) D) Coarse sand grains
- Correct Answer: C
- Rationale: Fine particles (≤2.5 μm) escape nasal hair and mucociliary clearance mechanisms, lodging deep within pulmonary alveoli and entering the bloodstream.
Q75. The atmospheric phenomenon where a layer of warm air settles over a layer of cooler air near the ground, trapping air pollutants close to the earth’s surface and preventing vertical dispersion is called: A) Acid deposition B) Thermal Inversion C) Greenhouse effect D) Stratospheric thinning
- Correct Answer: B
- Rationale: Thermal inversion reverses normal temperature gradients. The warm air cap prevents upward mixing, trapping emissions in the breathing zone.
Q76. Which gaseous air pollutant is primary responsible for the formation of “Acid Rain” when it reacts with atmospheric moisture to form sulfuric acid? A) Methane (CH4) B) Sulfur dioxide (SO2) C) Carbon dioxide (CO2) D) Argon (Ar)
- Correct Answer: B
- Rationale: Fuel combustion containing sulfur releases SO2, which oxidizes and hydrates in the atmosphere into H2SO4, causing acid precipitation.
Q77. What instrument is universally used by Environmental Health practitioners to measure ambient noise levels in workplaces or community environments? A) Anemometer B) Sound Level Meter C) Lux meter D) Barometer
- Correct Answer: B
- Rationale: A sound level meter captures acoustic pressure variations, converting them into decibel (dB) readings.
Q78. In the context of global environmental health, which class of synthetic chemical compounds is primary responsible for the depletion of the stratospheric ozone layer? A) Greenhouse carbon dioxide B) Chlorofluorocarbons (CFCs) C) Organophosphate compounds D) Volatile nitrogen oxides
- Correct Answer: B
- Rationale: CFCs drift into the stratosphere, where solar UV radiation breaks them down to release chlorine radicals that catalytically destroy ozone molecules.
Q79. What is the standard international threshold unit used to measure the intensity of sound waves relative to human hearing? A) Parts Per Million (ppm) B) Decibel (dB) C) Milligrams per cubic meter (mg/m3) D) Nephelometric Turbidity Units (NTU)
- Correct Answer: B
- Rationale: The decibel is a logarithmic unit used to quantify sound pressure levels.
Q80. Which radioactive gas can accumulate to dangerous levels inside the basements of homes built on specific granite soils, posing a high risk for lung cancer? A) Radon gas B) Helium gas C) Neon gas D) Chlorine gas
- Correct Answer: A
- Rationale: Radon-222 is a naturally occurring radioactive gas formed by uranium decay in soil and rocks. It seeps into buildings through foundation cracks and acts as a potent carcinogen.
Thematic Area 9: Environmental Impact Assessment (EIA)
Q81. In the standard Environmental Impact Assessment (EIA) process, what is the primary purpose of the “Screening” stage? A) To predict the exact magnitude of environmental changes B) To determine whether a proposed development project requires a full EIA or not based on legal thresholds C) To audit the environmental compliance of an operating factory D) To select the financial funding agency for the project
- Correct Answer: B
- Rationale: Screening is the initial step that evaluates project proposals to decide if their environmental impacts warrant formal, detailed EIA review.
Q82. Which step in the EIA process focuses on identifying the key environmental issues, alternatives, and boundaries that must be investigated in detail during the full assessment study? A) Mitigation planning B) Scoping C) Public auditing D) Project decommissioning
- Correct Answer: B
- Rationale: Scoping refines the focus of an EIA, identifying critical issues and establishing terms of reference to avoid wasting resources on minor impacts.
Q83. What is the primary focus of an Environmental Management Plan (EMP) developed within an EIA report? A) To maximize the stock dividend values for project investors B) To detail the specific mitigation measures, monitoring schedules, and institutional responsibilities designed to manage negative impacts C) To list the academic biographies of the assessment consultants D) To document the history of the industrial revolution
- Correct Answer: B
- Rationale: An EMP acts as an operational blueprint, detailing how identified impacts will be mitigated, monitored, and managed over a project’s lifecycle.
Q84. Under the Ethiopian Environmental Impact Assessment Proclamation (No. 299/2002), which type of project legally requires a mandatory full EIA before receiving an operational license? A) Opening a small neighborhood retail boutique shop ) Construction of a large-scale chemical manufacturing industry or major hydro-electric dam C) Repainting an existing administrative office building D) Planting flowers in a residential private garden
- Correct Answer: B
- Rationale: Proclamation 299/2002 mandates full EIAs for projects with high potential for transboundary or significant negative impacts, such as major dams, chemical factories, and mining operations.
Q85. What does the term “Mitigation” mean in Environmental Impact Assessment practice? A) Delaying project implementation until public opposition subsides B) Measures taken to avoid, minimize, rectify, or compensate for adverse environmental impacts resulting from project activities C) Paying financial bribes to regulatory authorities D) Completely stopping all forms of industrial infrastructure development globally
- Correct Answer: B
- Rationale: Mitigation encompasses steps designed to reduce structural damage to ecosystems by preventing, reducing, or offsetting negative impacts.
Q86. Why is “Public Participation” considered a critical legal component of the EIA process? A) It allows developers to sell shares to community members directly B) It ensures transparency, gathers local knowledge, and incorporates the concerns of affected communities into decision-making C) It extends the project completion timeline indefinitely D) It helps select the cheapest construction contractors available
- Correct Answer: B
- Rationale: Involving stakeholders ensures that democratic inputs, localized knowledge, and social equity issues are considered during regulatory reviews.
Q87. Conducting an assessment of the potential consequences of a project on human health parameters, such as changes in water-borne disease vectors or nutritional status, is technically known as: A) Strategic Environmental Assessment (SEA) B) Health Impact Assessment (HIA) C) Ecological Risk Profiling D) Economic Cost-Benefit Analysis
- Correct Answer: B
- Rationale: HIA uses specialized tools to estimate a policy or project’s potential effects on community health and distribution of health outcomes.
Q88. Which type of assessment extends EIA principles upstream to evaluate the environmental impacts of broad high-level initiatives like national policies, master plans, and development programs? A) Project-level EIA B) Strategic Environmental Assessment (SEA) C) Post-project Environmental Audit D) Baseline Ecological Survey
- Correct Answer: B
- Rationale: SEA applies predictive environmental frameworks to policies, plans, and programs (PPPs) rather than localized individual projects.
Q89. Who bears the financial cost of conducting an Environmental Impact Assessment study according to the “Polluter Pays Principle” and Ethiopian law? A) The local rural community members B) The federal environmental regulatory authority C) The project proponent (developer) D) Non-governmental charitable organizations
- Correct Answer: C
- Rationale: The developer or project proponent is legally responsible for funding the EIA study and implementing the resulting environmental management commitments.
Q90. What is the main objective of a “Post-Project Environmental Audit”? A) To check if the project has achieved its maximum sales targets B) To compare actual field impacts against predictions made in the EIA report and verify compliance with mitigation requirements C) To rewrite the original environmental legislation framework D) To dissolve the project management committee
- Correct Answer: B
- Rationale: Environmental auditing checks performance against baseline criteria and EIA expectations, ensuring accountability and improving future predictive models.
Thematic Area 10: Epidemiology and Biostatistics
Q91. An Environmental Health Officer investigates an outbreak of acute watery diarrhea in a district. They calculate the total number of new cases divided by the total population at risk during that specific week. What epidemiological measure is this? A) Prevalence rate B) Incidence rate (Attack rate) C) Case-fatality ratio D) Crude mortality rate
- Correct Answer: B
- Rationale: Incidence measures the velocity of new disease cases appearing in a population at risk over a specified timeframe.
Q92. Which study design selects a group of individuals exposed to a specific risk factor (e.g., uranium miners) and a group of unexposed individuals, following them forward in time to compare disease development? A) Cross-sectional study B) Case-control study C) Cohort study D) Randomized Controlled Trial (RCT)
- Correct Answer: C
- Rationale: Cohort studies are observational designs that follow subjects forward from exposure status to outcome development, enabling direct calculation of Relative Risk (RR).
Q93. An investigator wants to compare the occurrence of cholera between two villages. In Village A, 45 out of 500 people developed cholera. What is the calculated risk (cumulative incidence) of cholera in Village A? A) 1.0% B) 9.0% C) 45% D) 90%
- Correct Answer: B
- Rationale: Risk=New Cases/Population at risk=45/500=0.09, or 9.0%.
Q94. Which measure of central tendency is calculated by adding all the values in a dataset together and dividing the sum by the total number of observations? A) Median B) Mode C) Arithmetic Mean D) Range
- Correct Answer: C
- Rationale: The mean is the mathematical average computed by summing observations and dividing by the count (n).
Q95. In an epidemiological study investigating the association between arsenic exposure in drinking water and skin cancer, the calculated Odds Ratio (OR) is 4.2. How should this finding be interpreted? A) Arsenic exposure is protective against skin cancer B) Individuals exposed to arsenic are 4.2 times more likely to develop skin cancer compared to unexposed individuals C) Arsenic exposure has no statistical relationship with skin cancer D) Skin cancer causes individuals to drink more water containing arsenic
- Correct Answer: B
- Rationale: An OR>1 denotes a positive risk association. An OR of 4.2 indicates that the odds of disease are 4.2 times higher in the exposed cohort.
Q96. What type of bias occurs in a case-control study when patients with a disease (cases) recall past environmental exposures more thoroughly and accurately than healthy individuals (controls)? A) Selection bias B) Recall bias C) Confounding bias D) Interviewer bias
- Correct Answer: B
- Rationale: Recall bias is a form of information bias that occurs when differential memory accuracy exists between cases and controls regarding historical exposures.
Q97. A statistical distribution that is symmetrical, bell-shaped, and where the mean, median, and mode are all equal to each other is known as a: A) Positively skewed distribution B) Normal (Gaussian) distribution C) Binomial distribution D) Poisson distribution
- Correct Answer: B
- Rationale: The normal distribution is perfectly symmetrical about its center, aligning the mean, median, and mode at the peak.
Q98. In biostatistics, the probability value (p-value) is used to decide whether to reject the null hypothesis. If a study yields a p-value of 0.02 at a standard significance level (α=0.05), what should the researcher conclude? A) Accept the null hypothesis because the result is due to random chance B) Reject the null hypothesis; there is a statistically significant association C) The study is invalid and must be completely discarded D) The sample size was too large to draw any meaningful conclusions
- Correct Answer: B
- Rationale: A p-value<0.05 indicates that the observed data is highly unlikely under the null hypothesis, making the findings statistically significant.
Q99. What epidemiological term defines the continuous, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health practice? A) Environmental screening B) Public health surveillance C) Random sampling D) Clinical trial auditing
- Correct Answer: B
- Rationale: Surveillance serves as an early-warning system for public health networks, tracking disease patterns to guide interventions.
Q100. Which variable type is classified as a “Qualitative or Categorical Variable”? A) Blood lead concentration measured in μg/dL B) Daily volume of wastewater discharged in liters C) Type of household water source (e.g., Protected Well, Surface Water, Tap Water) D) Air temperature recorded in degrees Celsius
- Correct Answer: C
- Rationale: Categorical variables represent discrete qualitative groups or classifications rather than numerical values on a continuous scale.