Contaminants in Pet Food. The Safety of Food for Our Pets

Why does the topic of contamination in pet food still surprise manufacturers and owners?

At first glance, kibble or canned dog food is just… food. However, what is invisible – trace amounts of mycotoxins, heavy metals, pesticide residues, dioxins, or pathogens – can turn a daily meal into a health threat for your animal. That’s why control and analysis are not a luxury, but a fundamental part of the manufacturing and distribution of pet food.

The Scale of the Problem and Why We Can’t Assume “It’s Just Pet Food”

Contaminants in feeds and pet foods come from various sources: plant and animal raw materials can already contain pesticide residues, mycotoxins, or heavy metals when received at the facility; the production process and storage can introduce additional contaminants (e.g. through contact with contaminated packaging, production lines, or improper additives). Additionally, importing raw materials from regions with different agricultural standards increases the risk. The consequences may include acute poisoning, chronic health problems in animals, and also risk to humans in case of improper handling (e.g. contamination with zoonotic bacteria).

Quality control in pet food production must therefore combine the assessment of raw materials, processes, and the finished product – this is not only the responsibility of manufacturers but also analytical laboratories, inspection authorities, and distribution networks. EU and national laws set out frameworks regulating safety requirements for feeds and pet foods.

Main Categories of Contaminants Found in Pet Food

Below is an overview of the most important groups of contaminants – those that most often appear in quality control and have the greatest health significance.

1. Mycotoxins (aflatoxins, ochratoxin A, DON, fumonisins)
   Mycotoxins are toxic metabolites of molds (mainly Aspergillus, Fusarium, Penicillium), which may be present in grains, seeds, and plant raw materials used in food. In animals, symptoms depend on the type of mycotoxin, dose, and duration of exposure – from digestive disorders and immune suppression to liver damage and cancer development (e.g. in the case of aflatoxins). The risk is particularly significant in poorly stored raw materials or those harvested under unfavorable weather conditions. Risk assessment institutions (including the European Food Safety Authority – EFSA) continuously monitor the incidence and impact of mycotoxins in the food chain.
2. Heavy metals (lead, arsenic, cadmium, mercury)
   Heavy metals may derive from contaminated environments, seeds, fish (e.g. mercury), fertilizers, or mineral additives. Long-term exposure even to low doses can lead to accumulation in the body and result in chronic health problems.
3. Pesticide and insecticide residues
   Chemical residues used in agriculture can enter feeds and food, especially if the raw materials come from intensively cultivated fields. Although many substances have established residue limits, their presence requires monitoring, especially in ingredient blends and with raw materials imported from regions with different agrotechnical practices.
4. Dioxins, PCBs, and polycyclic aromatic hydrocarbons (PAHs)
   Substances that are difficult to remove, accumulated in fats – may appear in animal raw materials (e.g. fats, fish meal) as a consequence of incorrectly conducted production processes or environmental contamination. They have the potential for long-term toxic effects – including carcinogenic and immunotoxic effects. Studies and risk assessments in the EU also include these groups of contaminants.
5. Biological contaminants: bacteria, molds, and viruses
   Salmonella, Listeria, E. coli, or some parasites may end up in food, especially in wet products or under poor thermal processing and packaging conditions. The threat concerns both animal health (acute infections) and – when it comes to specific pathogens – human health through handling food. Hence the requirements for hygiene and appropriate testing before releasing a product onto the market.
6. Adulteration (e.g. melamine)
   Examples from the past show that adding substances to “enhance” nutritional value (specifically “protein content”) can lead to serious health crises. Reliable testing of composition and identification of protein sources are thus extremely important in this context.

Legal Framework: Which Regulations Apply to Pet Food?

Pet food is formally classified as feed. In the European Union, the main legislation producers should be aware of includes, among others, regulations covering feed hygiene, market placement requirements, and limits for certain contaminants. Key elements:

• Regulations on the marketing and use of feed (including Regulation (EC) No 767/2009) – sets out general rules on placing feed on the market, labeling, and user information.
• Regulations concerning feed hygiene and production requirements (including Regulation (EC) No 183/2005 and guidelines for its application). These regulations set obligations related to HACCP systems, registration, and inspection of feed producing plants.
• Acts setting maximum levels of certain contaminants (e.g. Directive 2002/32/EC of the European Parliament and of the Council of 7 May 2002 laying down maximum levels for undesirable substances in animal feed, including aflatoxin B1, dioxins, or metals). Commission rules set limits for specific contaminants, and EFSA provides scientific risk assessment.

In Poland, the classification, supervision, and detailed implementation rules for feed law are supplemented by national institutions (e.g. Veterinary Inspection) – manufacturers and distributors are advised to be familiar with local guidelines and inspection practices.

Research Methods: How Do We Test for Contaminants and Why Does It Work?

Laboratories analyzing pet food use a wide range of techniques. The choice of method depends on the goal of the analysis (quantitative/qualitative), type of matrix (dry food, canned, raw material), and required sensitivity.

1. LC-MS/MS (high-performance liquid chromatography with tandem mass spectrometry)
   A commonly used method for detecting and quantifying mycotoxins, pesticide residues, and a range of toxic metabolites. LC-MS/MS is highly sensitive, selective, and allows simultaneous determination of multiple analytes. It is the “method of choice” for testing pesticide and toxin residues.
2. GC-MS and GC-MS/MS (gas chromatography-mass spectrometry or tandem mass spectrometry)
   Suitable for the determination of volatile and semivolatile substances and some organic contaminants (e.g. PAHs). Often used in the analysis of pesticide residues or compounds formed during technological processes.
3. ICP-MS / ICP-OES (atomic plasma techniques)
   Used to determine heavy metals at very low concentrations (Pb, Cd, As, Hg). ICP-MS provides the sensitivity needed to assess compliance with permissible levels.
4. Microbiological and molecular methods (culture, PCR, rapid detection methods)
   For detecting Salmonella, Listeria, or other pathogens, both classical cultures and rapid PCR/real-time PCR tests are used, which allow fast identification and confirmation of results. Production hygiene control also requires regular environmental and finished product testing.

The GMP+ system is one of the most recognized and rigorous standards in the European feed sector. It covers both quality requirements and complete safety across the supply chain – from raw materials, through production, to transport and storage. It is not only a set of procedures, but a comprehensive risk management system aimed at one goal: guaranteeing that animal feed is free from chemical, physical, and microbiological hazards.

That’s why it’s so important that the J.S. Hamilton laboratory is officially registered in the GMP+ system for the identification of critical chemical contaminants. This registration confirms that our testing methods, equipment, validation processes, and team competence meet or exceed industry standards. Critical chemical contaminants in the GMP+ system include:

• Aflatoxin B1
• Dioxins
• Dioxin-like PCBs
• Non-dioxin-like PCBs
• Heavy metals: cadmium, arsenic, lead, mercury
• Fluorine
• Pesticides

In the area of other chemical contaminants, accreditation in accordance with the standard is required.

In practice, this means that our clients can benefit from tests that are accepted in international feed trade and provide a solid foundation for compliance with legal requirements and quality audits. GMP+ is a real guarantee of safety that we build together at every stage of our analyses.

Practical Example: How a Laboratory Verifies Suspected Mycotoxin Contamination

1. Receipt of samples at the laboratory – delivering a representative sample is key (adequate amount, correct collection method, and transport conditions)
2. Performing analyses – quantitative determination using appropriate analytical techniques
3. Test report – in addition to the results, comparison to criteria set out in law is possible.

This scheme enables fast and reliable determination of whether a problem exists, its scope, and action steps to undertake.

Conclusions – What Does This Mean for Manufacturers, Distributors, and Pet Owners?

1. There is no such thing as “zero risk”- what we have is risk management. Raw material control, regular testing, proper hygiene systems (HACCP/GMP), and cooperation with an accredited laboratory are the foundation. EU and national regulatory frameworks set minimum requirements; best practices must go further.
2. Raw materials are where the fight for safety truly begins. Supplier control, certificates, monitoring of seasonal materials, and a plan for preliminary tests minimize the risk of contaminants entering the process.
3. Laboratory testing = certainty of action. Using appropriate analytical methods (LC-MS/MS, GC-MS, GC-MS/MS, ICP-MS, PCR) allows for a reliable assessment and helps avoid false alarms.
4. Transparency and communication with the customer build trust. Access to test results (e.g. as part of contractor audits) and swift response in case of a problem are elements of responsible market strategy.

Solution: Specific Steps That Can Be Implemented in a Month, Quarter, and Year
Below is a practical action plan for pet food manufacturers who want to reduce contamination risk and demonstrate this to customers.

Within 1 month (quick operational actions):

• Ensure sampling procedures are up to date and staff are trained – a representative sample is 50% of analytical success.
• Create a list of critical raw materials and run laboratory tests for the most important ones.
• Check supplier documentation and request analytical certificates for new batches.

Within 3 months (systematics and monitoring):

• Develop a periodic testing plan (e.g. quarterly LC-MS/MS tests for selected mycotoxins and ICP-MS for metals).
• Order an audit of production and storage hygiene (drying conditions, humidity, inventory rotation).
• Establish procedures for handling non-compliant results (e.g. batch quarantine, supply chain tracing, communication with customers and authorities).

Within 12 months (strategy and communication):

• Implement a quality system compliant with relevant standards (e.g. GMP+, own safety KPIs).
• Maintain cooperation with an accredited laboratory (e.g. contract test program, rapid reporting, assistance with result interpretation).
• Be transparent toward clients: publish selected results and describe control procedures (this builds market advantage).

Most Frequently Asked Questions from Producers – Practical Answers

Do I have to test every package of food?
No – a reliable control plan is based on representative sampling and risk analysis. Each batch should have a specific sampling scheme tailored to production and raw materials.

How often should seasonal raw materials be tested?
The more variable the material quality (e.g. grains from different suppliers), the more often – at least with each new delivery batch and during high-risk seasons (post-drought, heavy rains).

Do laboratory results have legal validity?

Accredited laboratory results are the basis for technical and legal decisions (e.g. batch withdrawal). Depending on the country and situation, authorities may require such documents during inspections.

Pet food safety is a multi-layered issue: it starts in the field and ends in the pet’s bowl. Good production practices, conscious supply chain management, and reliable laboratory testing are the only way to minimize risk and build lasting customer trust.

If you want to move from theory to practice, J.S. Hamilton Poland laboratories offer a wide range of tests using highly sensitive techniques (including mycotoxins, metals, pesticide residues, microbiological studies), as well as result interpretation. Contact us – we will help you construct a testing program tailored to your raw materials and production processes.