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Environmental Yardstick for Pesticides

The Environmental Yardstick for Pesticides

Introduction :

J. Reus and P. Leendertse developed EYP for use in The Netherlands. EYP calculates a predicted environmental concentration in the compartments of groundwater, surface water, and soil. For each compartment, EYP first calculates a score based on a standard application rate of 1 kg/ha. After this standard score is calculated, it is multiplied by actual application rates to arrive at an EIP (environmental impact points) score. For groundwater concentrations, EYP relies on the PESTLA leaching simulation program or the PEARL leaching simulation program.


  • Reus, J., Leendertse, P. 1999. The environmental yardstick for pesticides (field crops). In J. Reus, P. Leendertse, C. Bockstaller, I. Fomsgaard, V. Gutsche, K. Lewis, C. Nilsson, L. Pussemier, M. Trevisan, H. van der Werf, F. Alfarroba, S. Blümel, J. Isart, D. McGrath, T. Seppälä (eds), Comparing Environmental Risk Indicators for Pesticides: Results of the European CAPER Project. Utrecht, The Netherlands: Centre for Agriculture and the Environment. 59-68.
  • Reus, J., Leendertse, P., Bockstaller, C., Fomsgaard, I., Gutsche, V., Lewis, K., Nilsson, C., Pussemier, L., Trevisan, M., van der Werf, H., Alfarroba, F., Blumel, S., Isart, J., McGrath, D., Seppala, T. 2002. Comparison and evaluation of eight pesticide environmental risk indicators developed in Europe and recommendations for future use. Agriculture, Ecosystems, and Environment 90, 177-187.
  • Tiktak, A., van den Berg, F., Boesten, J., van Kraalingen, D., Leistra, M., van der Linden, A. 2000. Manual of FOCUS PEARL version 1.1.1. RIVM report 711401008 / Alterra report 28. Bilthoven, The Netherlands: National Institute of Public Health and the Environment.

Reference Website:

Equations :

Groundwater :
For the groundwater compartment, the PEARL leaching simulation program calculates the predicted environmental concentration for a standard application of pesticide. That program takes into account such chemical information as the active chemical ingredient's half-life and Koc value as well as certain soil and meteorological conditions that are specific for each application site. After this predicted environmental concentration in groundwater is calculated by PEARL it is manipulated by EYP equations to determine an EIP score as shown in the following equation.

  • EIPgroundwater = [(PEARL PECgroundwater / 0.1μg/L)*100EIP]*[Application Rate]

In the equation, the 0.1μg/L value is the Dutch drinking water standard. As a result, any chemical that is predicted to exceed that 0.1μg/L standard will result in a score greater than 100 EIP and signify a violation of the Dutch standard for groundwater.

Surface Water :
In addition to groundwater, the EYP indicator also examines the amount of pesticide drifting onto nearby surface water and the potential danger to aquatic organisms that this may cause. To arrive at a predicted concentration in surface water, the EYP indicator uses the following formulas:

  • PECsurface water = (0.1)(1kg/ha)(emission% of pesticide to surface water/ditch depth)

  • EIPsurface water = [(PECsurface water / (0.1*LC50water organisms))* 100 EIP]*[Application Rate]

When specific ditch information is not available, an EYP default value of 25 cm is used. For our research, this value was used. The 0.1 value is again used as a scaling factor to arrive at a Dutch environmental standard. The LC50 water organisms value is for the most sensitive LC50 value for fish, daphnia, and algae.

Acute Soil :
The EYP indicator also arrives at a predicted concentration in soil. In the soil compartment, both the acute risk and the chronic risk are considered. The acute risk takes into account the amount of risk to soil organisms present immediately after the application event, while the chronic risk takes into account the amount of risk to soil organisms after two years. For the acute soil risk, an EIP acute soil score is calculated according to the following equations:

  • Amount of Soil Pesticide Applied to = 0.025*field size*soil bulk density

  • PECacute soil = 1/amount of soil pesticide applied to * 1000000

  • EIPacute soil risk = [(PECacute soil / 0.1*LC50worm))*100 EIP]*[Application Rate]
The EYP indicator assumes that the pesticide is distributed in the upper 0.025 meters of soil directly after application. For our research purposes, this 0.025 meters value was used to calculate the PECacute soil variable.

Chronic Soil :
EYP also considers the potential effect of a pesticide application on soil organisms after a time event of two years. This is the chronic soil risk of the pesticide application. For the chronic soil score the equations are:

  • PEC2 years = (% of pesticide in soil after 2 years) * (PECacute soil)

  • PECsoil moisture = PEC2 years/[(Kom*soil organic carbon content) + 0.2]

  • EIPchronic soil risk = [(PEC2 years / 0.1*NOECworms)*100 EIP]*[Application Rate]

Variables & Units :

Amount of Soil Pesticide Applied To (kg soil)
Application Rate (kg/ha)
Ditch depth (m)
Emission of Pesticide to Surface Water (%)
Field Size (Ha)
Kom (dm3/kg)
LC50worm (mg/kg)
NOECworm (mg/kg)
PEARL PECgroundwater (mg/L)
PEC2 years (mg/kg)
PECacute soil (mg/kg)
PECsurface water (mg/L)
Percentage of Pesticide in Soil After 2 Years
Soil Bulk Density (kg/m3)
Soil organic carbon content (%)

Analysis :

To arrive at the PEC 2 years variable, EYP first calculates a PEC in the soil for the upper 0.2 meters of soil. The upper 0.2 m is used because it is assumed that the pesticide will be distributed in this amount of soil in two years. The PEC 2 years value is then subject to a PESTLA graph that is included in the EYP article describing the system. This graph takes into account how much of the pesticide will degrade in the soil after two years. The graph has percentage lines that approximate how much of the pesticide is left in the soil after two years. These lines depend on the pesticide's Kom and half-life value. So for example, a pesticide with a half-life of 20 days and a Kom value of 60dm3/kg will have 0.01% of the original application amount remaining in the soil after two years. In contrast, a pesticide with a half-life of 160 days and a Kom value of 120 dm3/kg will have 10% of the original application remaining in the soil after two years. Unfortunately, the PESTLA graph used in the EYP description is for a soil with an organic matter content of 4.5%. Since the PESTLA system is no longer in use, application events that occur on soil with an organic matter content that is not 4.5% may be at a disadvantage when using this system.

Since NOEC worm values can be hard to find, the EYP system does allow a substitution. In this substitution, the PEC 2 years variable is converted into a PEC soil moisture variable and then NOEC water organism values are used to determine an EIP chronic soil risk score.

From the preceding discussion it can be seen that the EYP pesticide indicator considers the potential environmental effect of the pesticide application in four environmental compartments. These are the groundwater, the surface water, the acute soil, and the chronic soil compartments. The final values of these compartments stand alone and cannot be combined into one overall final risk score. Potential users of this model should also note that this indicator requires the use of either the PEARL or PESTLA leaching simulation program. However, these programs are fairly easy to use and readily available from the Internet.


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