Types of Plant Protection Products - Part 2

Types of Plant Protection Products - Part 2

Some plant protection products are toxic to people, but here we need to distinguish between acute and long-term toxicity. Acute toxicity manifests itself after direct contact with the toxin, whether through ingestion, absorption through skin or inhalation. In this case, the harmful effects occur more or less immediately. This is a risk for people working with pesticides, for example. The use of personal protection equipment is required such as gloves, masks and appropriate clothing when working with plant protection products in order to prevent acute intoxication.

By Ignacio García, CANNA Research

Read Types of plant protection products - Part 1

Are plant protection products hazardous to people?

Types of Plant Protection Products - Part 2

Long-term toxicity occurs as a result of repeated ingestion/contact with the product and is most common among consumers. Possible long-term intoxication is due to residue. Residue is defined as the plant protection substances that remain after treatment at a toxicologically significant level. Residue that is not toxic is referred to as ‘remains’.

Metabolites are also considered as residue and are produced as the plant protection product degrades into decomposition or reaction products where these continue to have toxic effects as defined above.

Once plant protection products have been used, they must disappear quickly from the environment to ensure that risks do not occur as a result of their toxic properties. The process of decomposition of the plant protection product after application is referred to as dissipation. An exogenous dissipation may occur because of plant growth or due to mechanical and physical causes such as, for example, rain. There are also chemical aspects that contribute to degradation such as hydrolysis, oxidation and photodecomposition processes (this is not an exhaustive list).

Another route for dissipation is through endogenous causes – that is, due to degradation processes that occur due to metabolism. In this case, metabolites are produced that may be harmless or toxic depending on the plant protection product that has been used.

The authorities set a maximum residue limit (MRL) that consumer products may result in, so that consumers are not exposed to the risk of toxicity. This parameter is linked to the ‘safety period’ – the time that elapses between applying the plant protection product and harvesting. The Lethal Dose 50 (LD50) parameter is used to assess toxicity. This parameter indicates the quantity of the active ingredient that leads to the death of 50% of the organisms on which tests are performed, using the route of ingestion. These tests are performed with laboratory animals such as mice and rats. Within the LD50 parameter, we can make a distinction between acute oral LD50 - where the product is ingested, acute dermal LD50 – where the product is applied to skin or Lethal Concentration 50 (LC50) - where the product is inhaled.

Types of Plant Protection Products - Part 2

‘No effect level’ (NEL) parameters are also used to indicate the quantity at which no harmful effects are perceived in organisms, such as problems with reproduction, teratogenesis, carcinogenesis, and so on. Based on the previous parameter, an Acceptable Daily Intake (ADI) level can be determined that indicates the quantity of plant protection product that may be ingested based in terms of body weight per day with no adverse effects on the organism.

The product is classified as category 1 (very toxic), category 2 (toxic) category 3 (harmful) and category 4 (low risk), depending on the product’s LD50 or LC50 parameters.

The label must bear a pictogram and a signal word (‘danger’ or ‘warning’) indicating the type of hazard involved when handling or using the pesticide. This must also include some hazard and precautionary statements.

Risk to land and aquatic animals

Some insecticides may cause significant harm to animal species near the location in which they are used, but their harmful effect may also extend to places further away due to the contamination of aquifers or because the products are washed into rivers and seas.

Types of Plant Protection Products - Part 2
We are all aware of the task that pollinating insects carry out and especially bees, which also produce valuable honey. Many plant protection products can be harmful to these insects and may, therefore, not be used on flowering crops or during the hours of the day when pollination takes place.

Plant protection products are classified as follows, depending on the risk they represent to land and aquatic animals:

  • Category A: Their use does not represent any risk as long as they are used correctly.
  • Category B: Moderate risk. These include products that can cause harm to land or aquatic animals if used incorrectly or in a non-controlled manner.
  • Category C: High or very high risk. These insecticides may cause significant harm if not used correctly and in areas where there is an important presence of fauna. The products that pose a risk to land animals may not be used in grasslands, pasture land, forest areas, humid areas and river networks. Products that entail a risk to aquatic animals are completely prohibited in humid areas and near rivers.
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