mobile feed weather

Visit our new site for advice on how to protect yourself when using pesticides.


Hazard, risk, human health and pesticides

Hazard, risk, human health and pesticides

The purpose of this four page section is to explain how governments and regulators assess the risk to human health associated with using a particular pesticide and seek to manage that risk. On this page we introduce the:

Key terms -hazard, exposure and risk - as relates to pesticides:

If exposure is managed such that absorption is non-existent or below a level that causes an effect (threshold dose), any chemical, however hazardous or toxic, can be handled safely.

Safety, evaluation and registration of pesticides

Pesticides are designed to control biological organisms. The same chemical properties that control pests may also harm humans thus there may be a risk of harm to human health if people are exposed to pesticides.   Huge efforts are made to avoid, manage and/or minimise that risk; governments create laws governing the development, sale and use of pesticides and develop regulatory frameworks to bring those laws to life. Industry works to increase awareness of the risks of using pesticides and to enable users to follow best practices.

In the vast majority of countries, pesticides undergo a rigorous safety evaluation and registration process before being placed on the market. In most countries this involves a ‘full assessment’ of the risks to human health and the most frequently used process by which to assess the safety of a pesticide to humans is to:

  1. Establish and classify how hazardous the pesticide is e.g. extremely hazardous, highly hazardous, moderately hazardous, slightly hazardous, unlikely to present a hazard in normal use. 
  2. Assess the risk of the pesticide being used to human health (e.g. by means of dose-response evaluation study, human exposure assessment and risk characterisation)
  3. Establish strategies for the management of that risk.

What is the difference between hazard and risk?

A hazard is something which is capable of causing harm e.g. a chemical, and which is classed as a hazard as a result of the intrinsic properties of the substance or object. It might be a physical hazard perhaps having the physical property of flammability (how easily something will burn), or it might be a chemical hazard such as an oxidiser (which can cause other substances to undergo a certain chemical reaction) or a toxicological hazard (such as causing a rash when contacting the skin). All these are hazards because they can potentially cause harm to people.

A hazard is classed as a hazard because it has the potential to cause harm. Yet because something is classed as a hazard doesn’t mean it will cause harm. As described above it also depends on the level or type of exposure. A wild animal such as a crocodile is a huge potential hazard, but if the crocodile is contained securely in a cage, there is no exposure and hence no harm. On the other hand many every-day objects can become hazards in certain exposure situations. For example a peanut can be fatal to a small child if inhaled into the airways.

A crocodile is a potential hazard, but if the crocodile is contained in a cage, then there is no exposure and hence no risk of harm.

The probability that harm occurs is defined as risk. Risk is a function of hazard and exposure. We can reduce the risk of harm from something that we perceive as inherently hazardous (such as a large crocodile) by eliminating exposure. We are exposed to multiple potential hazards every day but generally the risks are low and we do not come to harm. Very often we do take risks and we also avoid or minimise many others by using common sense and exercising caution.

Thus risks must be weighed up against the benefit of the activity/exposure situation.

How is the risk (associated with using a pesticide) to human health assessed?

Hazard, risk, human health and pesticides | Basic principles of toxicology | Assessing the risk to human health | Glossary - human health section