Chicken Embryo Test: The First Step in Pesticide Safety Evaluation
- What is PBT and Why is it Dangerous?
- The Importance of Pesticide Toxicity Testing
- What is Chicken Embryo Test?
- Application of the Chicken Embryo Test Method on Pesticide
Pesticides are chemical substances commonly used in the agricultural and livestock sectors to control pests, diseases, and weeds. Their use can increase crop productivity and improve the health of livestock. However, certain types of pesticides are classified as hazardous substances, such as Persistent, Bio-accumulative, and Toxic substances (PBTs).
What is PBT and Why Is It Dangerous?
PBTs are compounds that are difficult to break down in the environment, tend to accumulate in the fatty tissues of living organisms, and are toxic. When these pesticides are applied to food crops or livestock, residues can remain in food products such as vegetables, meat, milk, and even eggs. These residues can enter the food chain and eventually be consumed by humans.
Because PBT compounds are fat-soluble and not easily metabolized, they can accumulate in the human body and cause long-term effects, such as hormonal disruptions, organ damage, reproductive disorders, and an increased risk of cancer. The most concerning effects are on vulnerable groups such as pregnant women and fetuses, as these chemicals can negatively impact embryonic development.
The Importance of Pesticide Toxicity Testing
Exposure to pesticides during early development can lead to deformities, growth delays, or even fetal death. These concerns have prompted countries such as the European Union to establish Maximum Residue Limits (MRLs) for pesticides in plant- and animal-based foods to protect public health. As a preventive and monitoring measure, effective methods are needed to test the toxicity level of a pesticide before it is widely used.
One such method is the chicken embryo toxicity test. This test allows researchers to directly assess the effects of chemicals on embryonic development and serves as an initial step in ensuring pesticide safety for living organisms, including humans.
What is Chicken Embryo Test?
The Chicken Embryo Test (CET) is a toxicity testing method that uses fertilized chicken embryos as a model system to assess the effects of chemical substances, including pesticides, on the development of living organisms. This test has become one of the widely used approaches in toxicological research, as it provides an early indication of the potential hazards a compound may pose to health and the environment, particularly during embryonic development.
Chicken embryos are chosen for their various advantages, such as biological uniformity, ease of handling, and high sensitivity to chemical exposure. Moreover, chicken embryos closely resemble the developmental processes of other vertebrate embryos, including humans—especially in terms of growth stages and organogenesis. This similarity allows researchers to directly observe lethal effects as well as morphological abnormalities (teratogenic effects) caused by pesticide exposure, such as nervous system disorders, skeletal malformations, and embryo death.
However, in practice, the use of CET varies widely. In some developing countries or academic studies, CET is still used as part of preliminary toxicity testing due to its simplicity and relatively low cost. Meanwhile, in countries with stricter regulations like those in the European Union, this method is rarely used as primary data for pesticide registration. Nevertheless, CET is still maintained as a complementary method that can enrich information from other toxicological tests.
Application of the Chicken Embryo Test Method on Pesticide
In the chicken embryo test, there are two main methods used to apply the active ingredient of pesticides to the egg: the injection method and the immersion method. The eggs and embryos are examined through necropsy procedures on the 19th day of incubation. During the evaluation, several key parameters are observed, including embryo mortality rate, embryo body weight, and any developmental abnormalities present. Monitoring these parameters aims to assess the toxic or teratogenic effects of the test substance administered, whether by injection or immersion.
Injection Method
The most commonly used method is injection, in which the test substance is injected into a specific part of the egg, such as the air cell. In this method, the test substance (either as a single compound or in combination) is directly administered into the air cell of the chicken egg in a volume of 0.1 ml using a micropipette. Before injection, the blunt end of the egg is disinfected with 70% ethanol, and then the eggshell is drilled to create an entry point for injection.
After the substance is introduced, the hole is sealed with paraffin to prevent contamination or evaporation. This method offers several advantages, including avoiding physical injury to the embryo, allowing for precise dosing, and facilitating the calculation and evaluation of teratogenic changes due to the concentration of the administered chemical.
Immersion Method
The immersion method reflects a more natural exposure condition, as the entire egg is submerged in a chemical solution. In this method, chicken eggs are immersed in a solution or emulsion of the test substance for 30 minutes at room temperature. However, this method has a significant drawback: it is difficult to determine the exact amount of chemical that penetrates the egg.
This is due to factors such as varying eggshell permeability and environmental conditions like temperature and humidity. Each method has its own advantages and limitations, so the choice of method depends on the specific objectives of the toxicological study being conducted. Before pesticides are used in the field, ensure their active ingredients have undergone toxicity testing in a reputable laboratory.
Read more:
3 Recommended Pesticide Lab Tests to Pass the Ministry of Agriculture’s Distribution Permit!
Laboratory testing not only helps ensure safety for humans and animals but also protects the environment from the risk of hazardous chemical accumulation. Proper testing is key to creating pesticide products that are both effective and safe to use.
Author: Dherika
Editor: Sabilla Reza
References:
Hamid, A., Yaqub, G., Sajid, R.A., & Nida, A. (2017). Assessment of Human Health Risk Associated with the Presence of Pesticides in Chicken Eggs. Food Sciences and Technology, 37(3), 378-382. http://dx.doi.org/10.1590/1678-457X.11616.
Lehel, J., Szemeredy, G., Rita, S., Laszlo, M., Adrienn, G., & Peter, B. (2021). Reproductive Toxicological Changes in Avian Embryos Due To A Pesticide And An Environmental Contaminant. Acta Veterinaria Hungarica, 69(4), 363-371. DOI: 10.1556/004.2021.00043.
Pourmirza, A.A. (2000). Toxic Effects of Malathion and Endosulfan on Chick Embryo. J. Agr. Sci. Tech., 2, 161-166.
