Toxicology [2-Mark] Questions and Answer

 

Toxicology – 2-Mark Questions

1. Define toxicology and mention its major branches.

Toxicology is the scientific study of the adverse effects of chemical substances on living organisms, including their mechanisms, diagnosis, prevention, and treatment.

Major branches of toxicology include:

1.    Descriptive toxicology – studies and describes toxic effects of substances.

2.    Mechanistic toxicology – studies the mechanism by which toxic substances produce injury.

3.    Regulatory toxicology – applies toxicological data for setting safety standards and regulations.

4.    Clinical toxicology – deals with diagnosis and treatment of poisoning in humans.

5.    Forensic toxicology – deals with poisons in medico-legal investigations.

 

2. What is meant by toxicity? List its different types.

Toxicity is the ability of a substance to produce harmful or adverse effects in a living organism.

Types of toxicity based on duration of exposure include:

1.    Acute toxicity – adverse effects occurring after a single or short-term exposure.

2.    Subacute toxicity – effects occurring after repeated exposure for a relatively short period.

3.    Subchronic toxicity – effects produced by repeated exposure over a longer period.

4.    Chronic toxicity – adverse effects resulting from prolonged or repeated exposure.

5.    Local toxicity – effect occurs at the site of contact.

6.    Systemic toxicity – substance is absorbed and produces effects at distant organs.

 

3. Define poison and classify poisons with suitable examples.

A poison is any substance that, when introduced into the body in a sufficient amount, can cause harmful effects, illness, or death by its chemical action.

Poisons can be classified as:

1.    Corrosive poisons – cause tissue destruction.

Example: Sulfuric acid, sodium hydroxide.

2.    Irritant poisons – produce inflammation and irritation.

Example: Arsenic compounds.

3.    Neurotic poisons – mainly affect the nervous system.

Example: Opioids, strychnine.

4.    Cardiac poisons – mainly affect the heart.

Example: Digoxin.

5.    Asphyxiant poisons – interfere with oxygen utilization or transport.

Example: Carbon monoxide, cyanide.

 

4. Mention the major factors influencing toxicity.

The toxicity of a substance depends on several factors:

1.    Dose – generally, greater dose produces greater toxic effects.

2.    Route of exposure – oral, inhalation, dermal, injection, etc., can produce different toxicity.

3.    Duration and frequency of exposure – repeated or prolonged exposure may increase toxicity.

4.    Age – children and elderly persons may be more susceptible.

5.    Body weight and nutritional status – affect distribution and metabolism.

6.    Sex and genetic factors – may influence metabolism and response.

7.    Health status – liver, kidney, or respiratory disease can alter toxicity.

8.    Interactions with other chemicals or drugs – may increase or decrease toxicity.

 

5. List the important routes of exposure to toxic substances.

The major routes through which toxic substances enter the body are:

1.    Oral route – ingestion through the mouth; common in accidental or intentional poisoning.

2.    Inhalation route – breathing toxic gases, vapours, fumes, or dust.

3.    Dermal route – absorption through the skin.

4.    Ocular route – exposure through the eyes, mainly causing local toxicity.

5.    Injection/parenteral route – entry through intravenous, intramuscular, subcutaneous, or other injections.

6.    Mucosal route – absorption through mucous membranes.

The route of exposure affects the rate and extent of absorption and therefore the severity of toxicity.

 

6. What are EPA and WHO toxicity categories?

EPA toxicity categories are classifications used by the U.S. Environmental Protection Agency to indicate the acute toxicity of pesticide products. They are generally divided into Categories I–IV, with Category I representing the highest acute toxicity and Category IV the lowest.

WHO pesticide hazard classification categorizes pesticides according to their acute toxicity, mainly based on LD₅₀ values.

WHO classes include:

• Class Ia – Extremely hazardous
• Class Ib – Highly hazardous
• Class II – Moderately hazardous
• Class III – Slightly hazardous
• U – Unlikely to present acute hazard under normal use

These classifications help in safe handling, labeling, regulation, and risk management.

 

7. Define risk assessment and mention its major steps.

Risk assessment is the scientific process of estimating the likelihood and severity of harmful effects resulting from exposure to a hazardous substance.

The major steps are:

1.    Hazard identification – identifies whether a substance can cause harmful effects.

2.    Dose-response assessment – determines the relationship between dose and adverse effect.

3.    Exposure assessment – determines how much, how often, and by which route people are exposed.

4.    Risk characterization – combines hazard, dose-response, and exposure information to estimate the overall risk.

Mnemonic: HDER → Hazard → Dose → Exposure → Risk.

 

8. Differentiate between risk perception and risk management.

Risk Perception	Risk Management
It is the way people understand or judge a risk.	It is the process of controlling or reducing the risk.
It is influenced by fear, knowledge, experience, media, and culture.	It is based on scientific evidence, regulations, and control measures.
It describes how risky a situation is perceived to be.	It decides what actions should be taken to reduce risk.
Example: Public fear about pesticide exposure.	Example: Setting exposure limits and using protective equipment.

Thus, risk perception is about understanding/judging risk, whereas risk management is about controlling it.

 

9. What are the normal vital signs assessed in a poisoned patient?

The important vital signs assessed in a poisoned patient are:

1.    Body temperature: approximately 36.5–37.5°C

2.    Pulse rate: approximately 60–100 beats/minute in a healthy adult.

3.    Respiratory rate: approximately 12–20 breaths/minute in an adult.

4.    Blood pressure: approximately 90/60 to 120/80 mmHg in many healthy adults.

Oxygen saturation (SpO₂) and level of consciousness are also very important during toxicological assessment.

Abnormal vital signs may provide clues to the type and severity of poisoning.

 

10. State two important precautions/limitations associated with activated charcoal therapy.

Two important precautions/limitations of activated charcoal are:

1.    Risk of aspiration: It should generally be avoided in patients with reduced consciousness or an unprotected airway, because aspiration can cause serious pulmonary complications.

2.    It does not adsorb all poisons: It is ineffective or poorly effective for substances such as iron, lithium, alcohols, and many simple inorganic substances.

Activated charcoal should therefore be used selectively, after considering the poison, timing, and patient's airway condition.

 

11. Explain the ABC approach in the initial management of poisoning.

The ABC approach is the basic initial approach used to stabilize a poisoned patient:

• A – Airway: Assess whether the airway is open and protected. Remove secretions or obstruction and provide airway support if necessary.
• B – Breathing: Assess respiratory rate, effort, and oxygenation. Give oxygen and provide assisted ventilation if breathing is inadequate.
• C – Circulation: Assess pulse and blood pressure, establish IV access, give appropriate fluids, and manage shock or arrhythmias.

The priority is to stabilize life-threatening problems first, before detailed identification of the poison.

 

12. What are antidotes? Mention their role in the management of poisoning.

Antidotes are substances that prevent, neutralize, or reverse the toxic effects of a poison or drug.

Roles of antidotes:

1.    They may directly block the action of a poison.

2.    They may bind or chemically inactivate the toxic substance.

3.    They may prevent formation of toxic metabolites.

4.    They may restore substances depleted by the poison.

5.    They can reduce morbidity and mortality in specific poisonings.

Examples:

• Naloxone → opioid poisoning
• N-acetylcysteine → paracetamol poisoning
• Atropine → organophosphate poisoning

Antidotes are used along with supportive and symptomatic treatment.

 

13. Define NOEL, NOEAL, LOEL & LOEAL.

• NOEL – No Observed Effect Level: The highest tested dose or exposure level at which no effect is observed compared with the control.
• NOEAL – No Observed Effect Adverse Level: The highest exposure level at which no adverse effect is observed.
• LOEL – Lowest Observed Effect Level: The lowest tested dose or exposure level at which an effect is observed.
• LOEAL – Lowest Observed Effect Adverse Level: The lowest exposure level at which an adverse effect is observed.

These values are useful in dose-response assessment and risk assessment.

 

14. Differentiate between hazard and risk in toxicology.

Hazard	Risk
Hazard is the inherent ability of a substance to cause harm.	Risk is the probability that harm will actually occur under particular exposure conditions.
It depends mainly on the toxic properties of the substance.	It depends on hazard and exposure.
Example: Cyanide has a high toxic hazard.	The risk depends on how much cyanide a person is exposed to and by what route.

In short:

Hazard = potential to cause harm

Risk = likelihood of harm occurring

 

15. Mention any two important factors that influence toxicity.

Two important factors influencing toxicity are:

1.    Dose: The amount of toxic substance entering the body strongly affects the severity of toxic effects. Generally, a higher dose produces a greater toxic response.

2.    Route of exposure: The route, such as oral, inhalation, dermal, or injection, affects absorption and distribution. For example, inhalation may produce rapid systemic effects for some substances.

Other factors include age, body weight, duration of exposure, genetics, health status, and interactions with other substances.

 

16. What is a toxidrome? Mention any two examples.

A toxidrome is a recognizable group of signs and symptoms produced by poisoning with a particular class of toxic substances.

It helps clinicians identify the likely poison when the exact substance is unknown.

Examples:

1.    Opioid toxidrome: CNS depression, respiratory depression, and pinpoint pupils (miosis).

2.    Anticholinergic toxidrome: Dilated pupils, dry skin, tachycardia, urinary retention, and altered mental status.

Other examples include cholinergic and sympathomimetic toxidromes.

 

17. Write two important principles for the management of convulsions in poisoning.

Two important principles are:

1.    Stabilize ABC and correct reversible causes: Maintain airway and breathing, provide oxygen/ventilatory support when required, and check and correct hypoglycemia and major electrolyte abnormalities.

2.    Use benzodiazepines as first-line treatment: Drugs such as diazepam or lorazepam are commonly used to control toxicological seizures.

The suspected poison should also be identified and specific treatment/antidote given when available, such as pyridoxine in isoniazid poisoning.

 

18. Mention two methods of elimination enhancement used in poisoning.

Two important methods of enhanced elimination are:

1.    Urinary alkalinization: Administration of sodium bicarbonate can increase renal excretion of certain weak acids, especially salicylates, by ion trapping in the renal tubules.

2.    Hemodialysis: An extracorporeal technique that removes certain toxic substances from the blood. It may be useful in selected severe poisonings such as lithium, methanol, ethylene glycol, and severe salicylate poisoning.

Other methods include multiple-dose activated charcoal and, in selected situations, continuous renal replacement therapy.

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