Risk assessment of plant protection products

The authorization of a plant protection product requires that, when the product is used correctly and in line with its intended purpose, the protection of the health of all groups of people who may come into contact with the pesticide or its residues is ensured. In order to achieve this, toxicological effects must be identified and quantified. Furthermore, for each group of people who may be exposed to the plant protection product, the amount of the product they can come into contact with must be estimated (exposure).

Risk assessment procedure

The risk is determined by comparing the toxic effect of the product with the exposure. Additional risk mitigation measures may be specified if necessary.

People can come into contact with plant protection products in various ways:

• Users can be exposed to plant protection products or their components through the skin or through inhalation during application, as can people carrying out follow-up work on the treated area.
• People who live or work in the vicinity of the treated areas or people who happen to be in the area during application (e.g. people walking by) can be exposed to plant protection products or their components through the skin, through inhalation or, in the case of small children, through the mouth.
• Consumers may ingest residues of plant production products via food.

Risk assessment diagram

Identification of toxic effects

In order to ensure that the application of plant protection products does not pose an unacceptable risk to humans and animals, the products and the active substances they contain are evaluated and toxicologically assessed by BfR. This takes place before authorisation.

Plant protection products can be made up of a variety of components:

• Active substance(s); finished plant protection products usually contain one or two active substances; in individual cases, as many as four active substances may be present.
• Various co-formulants such as surfactants, preservatives, antioxidants, anti-foam agents, emulsifiers, and solvents.
• Safeners and synergists which influence the effect of active substances; safeners reduce potentially undesired effects on cultivated plants; synergists enhance the desired effect on the target organism.

The scope of toxicological analyses for plant protection products is regulated by law. Information on this subject can be found under Legal foundations.

Active substances which are to be used in plant protection products must undergo very extensive tests for potential adverse health effects:

• Toxicokinetics and metabolism (intake, metabolic processes and excretion)
• Acute toxicity (toxicity after one-time intake), skin and eye irritation, sensitisation (allergenic potential)
• Subchronic toxicity (toxicity after repeated dose exposure)
• Genotoxicity (mutagenic effect)
• Chronic toxicity (long-term toxicity)
• Carcinogenicity (cancer-causing potential)
• Reproductive and developmental toxicity (harmful effect on fertility and offspring)
• Neurotoxicity (harmful effect on the nervous system)
• Endocrine disrupting properties (harmful effect on the hormone system)
• Additional studies if necessary, e.g. on toxicological mechanisms of action

In addition, BfR assesses the following effects of the plant protection product submitted for authorisation:

• Acute toxicity (oral, dermal, inhalation)
• Irritation of skin and eyes, skin sensitisation
• Dermal absorption (uptake through the skin)

If necessary, further assessments may be carried out regarding the combination effects of plant protection product ingredients.

Derivation of limit values

Dose-response relationships are derived for the detected toxic effects. It is assumed that the majority of toxic effects are subject to a threshold value - in other words, an adverse health effect only occurs if a certain dose (threshold) is exceeded.

The NOAEL (no observed adverse effect level) serves as the basis for the determination of limit values. This is the dose at which no adverse health effects were observed in experimental studies. The NOAEL, taken from a study on rats for example, is divided by a(n) (un)certainty factor which not only accounts for the different sensitivities of humans and animals, but also the differences in sensitivity of individuals, and therefore includes particularly sensitive groups of people such as children, pregnant women or sick people. A factor of 100 is usually used for this. The following limit values are derived for active substances of plant protection products:

• ADI stands for "acceptable daily intake" and specifies the amount of a substance that consumers can ingest on a daily basis over a lifetime without any discernible health risk. The ADI represents a limit value for the long-term exposure of consumers.
• ARfD stands for "acute reference dose" and specifies the amount of a substance that consumers can ingest with food over one or more meals in the course of one day without any discernible health risk. The ARfD represents a limit value for the short-term exposure of consumers.
• AOEL stands for "acceptable operator exposure level” and represents the exposure limit for users of plant protection products and uninvolved third parties. These are people who come into direct contact with the plant protection product by chance either during or shortly after its application.

Substances with no derived limit value

It can be assumed that certain toxic effects are not subject to a threshold, meaning no exposure level can be identified that does not have a harmful effect. No limit values are derived for substances with these toxic effects. Carcinogenic substances in particular are not approved as active substances in plant protection products if they exhibit a mutagenic mechanism of action without a threshold value. This is regulated by Regulation (EC) No 1107/2009 concerning the placing of plant protection products on the market. Further information on this matter can be found under Legal foundations.

Exposure assessment

To assess a health risk, not only are data on toxicological effects required, but also on the exposure of the affected groups of people during or after the application of plant protection products in line with their intended purpose. To this end, the amount of plant protection products or their residues that can be taken up by humans is determined. The fact that different groups of people can be exposed in very different ways with regard to uptake path, duration and level of exposure is taken into account. Consumers, for example, can ingest residues of plant protection products through food (orally). This is evaluated as part of a comprehensive assessment of consumer safety and plant protection product residues.

During the application of plant protection products, users, workers (e.g. during follow-up work), residents or bystanders (e.g. people taking a walk) may inhale the product or absorb it through their skin. These uptake routes are taken into account in the assessment of the application safety of plant protection products.

Risk characterisation

For the assessment of health risks that may be caused by plant protection products, the possible exposure levels of the various groups of people are compared to the health-based limit values.

As long as the exposure level does not exceed the calculated limit values, there is no unacceptable health risk for users, uninvolved third parties or consumers.

Risk characterisation diagram

A plant protection product is therefore only authorised for an application when the expected exposure for users, workers, residents and bystanders is lower than the AOEL value determined in toxicological studies. If necessary, conditions are set for the safe handling of plant protection products (e.g. personal protective measures, the use of drift-reducing devices or waiting times etc.).

Furthermore, a plant protection product is only authorised when the expected intake of residues by consumers is lower than the ADI and ARfD limit values derived from toxicological studies. In order to assess lifelong exposure, the exposure level from an average amount of food and an average residue is calculated and compared to the ADI toxicological limit value. For the assessment of one-time exposure, the exposure level from a high amount of food and the highest expected/measured residue is calculated and compared to the ARfD toxicological value.

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