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Hazards, risks and safety precautions

Edexcel IAL Biology · WBI13 Practical Skills in Biology I

Risk assessment questions want you to separate a hazard, the risk it causes and a precaution that reduces that risk, and to explain each one.

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Hazard, risk and precaution

A hazard is something that could cause harm (a scalpel, hydrochloric acid, a microorganism, formalin).
A risk is the chance of harm from that hazard and what the harm is (cutting a finger; acid in the eye; infection).
A precaution (control measure) reduces the risk (cut away from the body on a tile; wear eye protection; aseptic technique).

The June 2024 report: 'You need to be very clear in your mind about the difference between a hazard, a risk and a strategy to reduce the risk.' Use different hazards in different rows.

Hazard	Risk	Precaution
Scalpel (dissection, CP6, CP7)	Cuts to skin	Cut away from the body onto a white tile
Hydrochloric acid (CP6)	Irritates or burns skin and eyes	Wear eye protection and gloves; use dilute acid
Bacteria on agar (CP9)	Infection if a pathogen grows	Aseptic technique; tape lid; incubate at no higher than about 25 to 30 °C
Hot water bath (CP3, CP4)	Scalds	Use tongs; keep below a safe temperature
Iodine or Benedict's	Irritant to eyes	Eye protection

Microbiology safety (CP9)

Sterilise equipment (autoclave, flame inoculating loops until red hot).
Work near a Bunsen flame so convection currents carry microbes away.
Open lids as little as possible.
Secure the lid with two strips of tape, not sealed all round, so oxygen can enter and anaerobic (often pathogenic) bacteria are not favoured.
Incubate at about 25 °C, not 37 °C, so human pathogens are less likely to grow.
Dispose of plates by autoclaving. Each precaution needs its reason.

Ethics and implications

Unit 3 can ask you to comment on the implications of the biology, such as benefits and risks, or social or environmental context. Examples: using animal organs from a butcher rather than killing animals for dissection; returning organisms to their habitat; respecting volunteers' informed consent.

Worked example

Complete a risk assessment row for using formalin-preserved fish in a dissection.

Hazard: formalin (toxic, irritant vapour).
Risk: breathing in vapour or skin and eye irritation.
Precaution: work in a well-ventilated room or fume cupboard, wear gloves and eye protection, wash hands afterwards.

Answer: Hazard: formalin. Risk: irritation of eyes, skin or airways. Precaution: ventilation or fume cupboard, gloves, goggles, washing hands.

Key idea: Hazard = what can harm; risk = the chance and type of harm; precaution = what reduces it, with a reason. In microbiology use aseptic technique, partial taping and 25 °C incubation.

Check yourself

In a root tip squash (CP6), which is the hazard?
- Burning the skin
- Wearing eye protection
- Hydrochloric acid
- The chance of acid splashing
Show answer
Hydrochloric acid. The acid is the hazard; burns are the harm; eye protection is the precaution.
Which statement describes a risk rather than a hazard?
- Cutting your finger when using a scalpel
- A scalpel
- Formalin
- Bacterial cultures
Show answer
Cutting your finger when using a scalpel. A risk describes the harm that could happen and its chance.
Why are agar plates taped with two strips rather than sealed all round?
- So the lid can be removed easily
- So the agar dries out quickly
- So oxygen can enter and anaerobic pathogens are less likely to grow
- So the plate can be stacked
Show answer
So oxygen can enter and anaerobic pathogens are less likely to grow. Sealing all round creates anaerobic conditions that favour some pathogens.
Why are school bacterial cultures incubated at about 25 °C rather than 37 °C?
- Bacteria cannot grow at 37 °C
- Human pathogens grow best near body temperature
- Agar melts at 37 °C
- Colonies are easier to count at 37 °C
Show answer
Human pathogens grow best near body temperature. Lower temperature reduces the chance of growing pathogens.
Why is work with cultures done near a lit Bunsen burner?
- The flame warms the agar
- It makes colonies grow faster
- It sterilises the bacteria being studied
- Rising air carries airborne microbes away from the plate
Show answer
Rising air carries airborne microbes away from the plate. Convection currents reduce contamination.
Explain one precaution when cutting plant tissue with a scalpel.
Show answer
Cut away from the body onto a white tile, so that if the scalpel slips it does not cut your hand.. A precaution plus the reason scores; a precaution alone does not explain.
Which is an ethical advantage of using a heart obtained from a butcher for dissection?
- The heart is easier to cut
- It has no blood vessels
- It is free of all microorganisms
- No animal is killed specifically for the practical
Show answer
No animal is killed specifically for the practical. The animal was slaughtered for food anyway.

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Last updated 8 November 2026. Spotted a mistake? Tell us.