Why is Acute Oral Toxicity Testing Important in the Safety Assessment of Microbial Biopesticides?

Microbial biopesticides are increasingly chosen as more environmentally friendly pest control agents. However, even though they are derived from natural microorganisms, these products still need to be evaluated for their safety in humans.

One important aspect assessed is the potential hazard when the product is accidentally ingested. Acute oral toxicity testing serves as an initial step to understand how the body responds to a single-dose exposure of the biopesticide.

The results can indicate whether short-term harmful effects occur, including signs of poisoning.

• The Importance of Acute Orak Toxicity Testing in the Safety Assessment of Microbial Biopesticides
• How Is Acute Oral Toxicity Testing Conducted in Animals According to Regulatory Standards?
• The Acute Toxicity Estimate (ATE) Method: An Non-Animal Alternative Still Under Debate

The Importance of Acute Orak Toxicity Testing in the Safety Assessment of Microbial Biopesticides

When people hear the word pesticide, they often think of chemicals. In reality, a growing number of pesticides are based on microorganisms—such as bacteria or fungi—which are considered more environmentally friendly.

Nonetheless, “natural” does not automatically mean “safe.” Microorganisms must still be assessed to determine whether they may cause toxic effects when entering the body, particularly through ingestion. This is where acute oral toxicity testing becomes crucial.

Acute oral toxicity testing is conducted to determine whether harmful effects occur after a person (or animal) accidentally ingests a certain amount of a microbial biopesticide. This is important because various exposure scenarios may arise, from improper storage to accidental food contamination.

If prior data or information is insufficient to ensure that a microorganism is safe, acute oral toxicity testing becomes an essential step in protecting users and consumers.

How Is Acute Oral Toxicity Testing Conducted in Animals According to Regulatory Standards?

Different countries or regulatory bodies have their own guidance documents, but for acute toxicity, two major references are the OECD guidelines and the US EPA guidelines.

In this test, rodents, typically rats, are given a single oral dose of the test substance (via oral gavage). The animals are fasted beforehand to ensure optimal absorption of the dose. After dosing, the rats are observed for a full 14-day period.

Researchers record various parameters, including changes in body weight, signs of poisoning, and mortality, if any occur. At the end of the observation period, a necropsy (a type of autopsy for animals) is performed to identify any damage or abnormalities in major organs.

These guidelines are outlined in standards such as OECD Test Guidelines 420 and 423, as well as US EPA Guideline 870.1100. Although the test may appear straightforward, it provides direct insight into how the body reacts to a microbial biopesticide formulation.

Read more:
Eco-Friendly Doesn’t Mean Risk-Free: Why Fungal Biopesticides Require Laboratory Testing?

The Acute Toxicity Estimate (ATE) Method: An Non-Animal Alternative Still Under Debate

As technology advances, scientists and regulators have begun searching for ways to reduce the use of animals in testing. One alternative approach currently being widely discussed is the Acute Toxicity Estimate (ATE).

Instead of conducting animal studies, the ATE method estimates toxicity based on the known toxicity data of each component in the formulation. The principle is additivity, in simple terms, the “total hazard” is assumed to be the sum of the hazards of its individual components.

Unfortunately, according to various studies, the ATE method is not yet fully reliable. Reported accuracy rates vary, some studies show 52%, others 43%, and some up to 75%.

More importantly, the method tends to underestimate toxicity in more hazardous formulations. This means that in some cases, ATE may present a product as “safer” than it truly is.

Because of this, although ATE holds potential as a supporting tool within a weight-of-evidence framework, it is not yet robust enough to replace in vivo testing entirely. For microbial biopesticides in particular, given their unique biological properties, matching toxicity data becomes even more complex.

Given the biological complexity of microbial biopesticides and the limitations of alternative methods such as ATE, pesticide laboratory testing is a critical step to ensure product safety before market release. Acute oral toxicity testing provides a strong scientific basis for assessing potential risks from accidental exposure and is an essential component of regulatory compliance and product registration.

To support these pesticide laboratory testing needs, IML Testing and Research offers acute oral toxicity testing services in accordance with OECD guidelines and applicable regulations. Testing is conducted in a standardized and well-documented manner to generate accurate, reliable, and defensible data, helping microbial biopesticide producers ensure product safety from early development through the approval process.

Author: Dherika
Editor: Sabilla Reza

References:

Hamm, J., Allen, D., Ceger, P., Flint, T., Lowit, A., O'Dell, L., Tao, J., & Kleinstreuer, N. (2021). Performance of the GHS Mixtures Equation for Predicting Acute Oral Toxicity. Regulatory toxicology and pharmacology : RTP, 125, 105007. https://doi.org/10.1016/j.yrtph.2021.105007.

Wend, K., Zorrilla, L., Freimoser, F.M., & Gallet, A. (2024). Microbial Pesticides – Challenges and Future Perspectives for Testing and Safety Assessment with Respect to Human Health. Environmental health, 23, 49, 1-29. https://doi.org/10.1186/s12940-024-01090-2.