Heavy Metals in Produce: The Silent Threat Everyone Must Know – With Complete Prevention Guidelines
Heavy Metals in Produce: The Silent Threat Everyone Must Know – With Complete Prevention Guidelines
In an era where Thai agricultural produce like durians, mangosteens, and export vegetables are gaining momentum and playing a vital role in global markets, the word “quality” goes beyond taste, appearance, or freshness. It also encompasses “safety” that must be ensured at every step of production — especially concerning contamination from heavy metals and prohibited chemicals, which are still commonly found in many production systems.
A recent case, such as the detection of BY2 Yellow in durians, highlights concerns over elevated cadmium levels—an effect linked to this type of dye. The contamination may stem from improper handling or raw material contamination, ultimately impacting international confidence in Thai exports.
Heavy metals such as lead, cadmium, arsenic, and mercury, along with agricultural residues that fall outside safety standards, can unknowingly enter produce—through water, fertilizer, soil, or the use of unauthorized chemicals. All of these factors directly impact consumer safety and the country’s reputation in the global trade arena.
Understanding the Root Causes of Heavy Metals – Deep Insight for Effective Prevention
Addressing the issue of heavy metals in the production of fruits and economic crops like durians, longans, or export vegetables is not something that can be overlooked. Heavy metal contamination doesn’t stem from a single cause but is often the result of accumulation from multiple sources—such as soil, water, fertilizers, or even non-compliant containers and equipment used during production.
Once heavy metals like lead, cadmium, or arsenic contaminate the soil or water sources, they can be directly absorbed by crops—affecting both the quality of the produce and long-term consumer health. This also impacts export potential, as many importing countries enforce strict residue testing standards.
Producers must therefore deeply understand the sources of contamination and apply appropriate prevention measures—such as regular soil and water testing, choosing safe fertilizers and soil amendments, and maintaining strict control over production processes. These steps are essential to ensure the safety of Thai agricultural products and to sustain trust in global markets.
1. Growing Soil – The Primary Source of Contamination
- Areas that were once industrial zones or located near major roads may contain lead residues accumulated over decades from vehicle emissions or factory pollutants.
- Soil subjected to intensive chemical farming often retains cadmium from various chemical fertilizers and pesticides—residues that are not easily washed away.
Guideline: Before each planting cycle, conduct at least one soil analysis. If contamination is suspected, consider switching to commercial growing media or hydroponic systems.
2. Irrigation Water – Invisible Yet Hazardous
- Groundwater in many parts of Thailand contains arsenic contamination from natural rock layers.
- Water from canals or natural sources that flow through industrial areas often carries high levels of contaminants.
Guideline: Install a Reverse Osmosis (RO) filtration system or test irrigation water every 3–6 months to ensure safety.
3. Fertilizers and Soil Amendments – A Controllable Factor
- Low-cost, uncertified fertilizers may contain raw materials contaminated with heavy metals.
- Organic fertilizers aren’t always safe either—especially if made from organic waste that hasn’t been screened for toxic substances.
Guideline: Use fertilizers that are Heavy Metal Certified and choose brands with internationally recognized manufacturing standards.
4. Post-Harvest Process – A Small Step Often Overlooked
- Low-quality metal pruning tools can release heavy metals onto the flowers during trimming.
- Trimming or cutting machines made from non–food grade materials are another potential contamination risk.
Guideline: Use equipment that meets GMP (Good Manufacturing Practice) standards and clean thoroughly before each use.
Heavy Metal Contamination – A Hidden Danger Passed from Plants to Consumers
Heavy metals don’t just affect plant growth—they pose serious health risks to consumers, especially when residues accumulate in produce that hasn’t been properly monitored.
Impact on Plants
- Heavy metal accumulation in plant roots reduces the absorption of other essential nutrients, preventing the plant from producing key compounds effectively—compounds that directly influence the potency and quality of the yield.
- If heavy metals remain in the plant, they can contaminate the final produce and pose serious health risks to consumers.
Guideline: Use fertilizers that are Heavy Metal Certified and choose brands with internationally recognized manufacturing standards.
Impact on Consumers
| Heavy metals and | their associated dangers |
Lead (Pb) | Damages the nervous system and increases the risk of long-term memory loss. |
| Cadmium - Cadmium (Cd) | damages the kidneys and increases the risk of lung and prostate cancer. |
| Arsenic (As) | accumulates in the liver and skin, causing stomach cancer. |
| Mercury (Hg) | interferes with fetal brain development and damages the reproductive system. |
Once contaminated, it remains in the produce permanently.
International Safety Standards
Table showing the standard values of heavy metals permitted in agricultural products according to European (EU) standards.
(Heavy Metal Limits in Agricultural Products as Regulated by EU)
| Heavy Metal | EU upper limit (2019/1009) | Note (Details according to EU regulations) |
| Cadmium - Cadmium (Cd) | ≤ 60 mg/kg P₂O₅ | It is used only with phosphate fertilisers, as natural phosphates may be highly contaminated with cadmium, therefore specific control values have been established. |
| Lead - Lead (Pb) | ≤ 120 mg/kg dry matter | Covers all types of materials in the PFCs (Plant Fertilising Products Components) group to prevent lead accumulation in plants and the environment. |
| Mercury - Mercury (Hg) | ≤ 1 mg/kg dry matter | Available in both powder and granular forms to limit the risk of absorption into plants and accumulation in the ecosystem. |
| Nickel - Nickel (Ni) | ≤ 100 mg/kg dry matter | Although not directly used in the manufacturing process, nickel may be contaminated from natural raw materials, so maximum control values are set for safety. |
| Arsenic (As) | ≤ 40 mg/kg dry matter | Use specific control values for “inorganic arsenic”, which is a highly toxic form and likely to persist in plants. |
| Chromium - Chromium (Cr) | ≤ 2 mg/kg (Cr(VI) only in growing media) | No total chromium (Total Cr) values were determined, but only the highly toxic hexavalent chromium (Cr(VI)) in the growing media was controlled. |
| Cobalt - Cobalt (Co) | Not specified | It is not on the main control list under Regulation (EU) 2019/1009 and therefore no official limit value has been specified. |
Guidelines for Heavy Metal Free Agriculture
Modern agriculture no longer focuses solely on attractive appearance or high yield—“safety” is now equally essential. Heavy metals contamination, in particular, poses direct risks to consumer health and may become a major barrier to entering international markets. The following guidelines offer practical steps for growers to implement safe production systems that align with international standards and comprehensively reduce the risk of heavy metal contamination.1. Set up the system from the beginning – starting from selecting a safe planting site
A strong foundation begins with assessing and evaluating the risks of the cultivation site—especially “soil” and “water,” which are critical factors influencing heavy metal uptake in plants.
- Conduct soil and water analysis before each planting cycle by sending samples to certified laboratories to assess heavy metal concentrations such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg).
- Choose growing media that have been tested and certified to be free from heavy metals, such as organic soil with verified test results or soil alternatives like peat moss or coco peat sourced from controlled origins.
- If cultivation in high-risk areas is unavoidable, use closed growing systems—such as planting in pots or using hydroponics—to avoid direct uptake of heavy metals from the soil.
2. Choose fertilizers and nutrients with standards – important factors that should not be overlooked
Fertilizers nourish plants, but if they lack proper standards, they can also become a source of heavy metal accumulation.
- Avoid using fertilizers or soil amendments without clear labeling or source information, as they may pose a high risk of contamination.
- Choose fertilizers certified by trusted authorities—such as organic fertilizers from GAP or GACP-certified sources, or specialized formulas with lab test results confirming they are free from heavy metal contamination.
- Always review and compare fertilizer information before use, and regularly send random samples for testing—especially when used in large quantities.
3. Closely monitor the growing environment – to control risks from external factors.
- Maintain soil pH between 5.5 and 6.5, as pH levels influence the plant’s ability to absorb metals. An optimal pH range reduces the likelihood of heavy metals being taken up by the roots.
- Cultivate in greenhouses or controlled environment agriculture (CEA) systems to prevent contamination from dust, polluted water sources, or uncontrolled environmental factors.
- Use clean water filtration systems or filters specifically designed to remove heavy metals before irrigation, preventing metal contamination through water.
4. Regularly review and record data – for transparency and traceability.
- Establish a systematic cultivation logbook to record key data such as sources of soil, fertilizers, water, and growing media.
- Systematically store all analysis results—both pre-planting assessments and product testing before distribution.
- Test all produce before distribution to ensure it is free from contamination, and retain the results as supporting evidence for marketing and legal purposes.
Heavy Metal Detection Technology – Essential Knowledge Every Grower Should Understand
Ensuring produce is free from heavy metals requires the use of highly accurate detection technologies. Each method has its strengths and limitations, so selecting the right one should depend on budget, required precision, and the specific objectives of the analysis.
1. ICP-MS (Inductively Coupled Plasma – Mass Spectrometry)
It is the highest-standard technology for heavy metal detection, capable of identifying elements at the “parts per billion (ppb)” level with exceptional sensitivity and precision. Ideal for research, industrial-scale production, and laboratories requiring in-depth data to comprehensively analyze product safety across all elements.
2. AAS (Atomic Absorption Spectroscopy)
This method uses the principle of light absorption by metal atoms, making it suitable for detecting specific heavy metals such as lead, cadmium, mercury, or arsenic. With lower costs compared to ICP-MS, it is commonly used in mid-level laboratories or when only specific elements need to be tested.
3. XRF (X-ray Fluorescence)
This technology is known for its speed and ability to analyze samples without complex preparation. It is ideal for field applications, such as preliminary screening on farms or at checkpoints to assess initial risk. However, its accuracy may be lower than other methods, making it unsuitable for official confirmation of results.
The challenge of modern cultivation systems lies in the rising standards, which, while ensuring better quality and safety, also result in higher costs.
Although analytical technologies clearly enhance agricultural safety, in practice, there are significant obstacles that growers, especially small-scale ones, must regularly face.
The high cost of analysis is a significant challenge.
Especially when using ICP-MS or AAS, which are standard methods, the testing cost in Thailand for one sample may start from 3,000 to 5,000 baht, making it difficult for small-scale producers to conduct regular testing as needed.
Soil in many areas has accumulated heavy metals over a long period.
The accumulation of heavy metals from the use of chemical fertilizers, soil amendments, or proximity to industrial areas requires time, long-term planning, and sufficient financial support for soil restoration.
Knowledge and access to information are still limited among certain groups of farmers.
This results in a lack of continuous safety management, with some growers still unaware of the serious risks posed by heavy metals.
Safe agriculture starts with us. We build standards through the collaboration of all sectors.
To create a safe and sustainable agricultural ecosystem, it is not only the responsibility of the growers but also requires the appropriate involvement of all sectors.
Consumers
- Consumers should choose products from reliable sources.
- Request a Certificate of Analysis (COA) every time to confirm that the product is free from harmful contaminants.
- Avoid products with unclear sources or those that cannot be traced back for verification.
Growers
- Plan production under GACP and GMP standards to ensure safety at every stage.
- Conduct soil and water quality tests at least twice a year, and test the produce after harvest every time before distribution.
- Systematically record the use of fertilizers, soil amendments, and other factors for future traceability in case any issues arise.
Exporters
- Study the laws and standards of the destination country in detail, as each country has different heavy metal control limits.
- Prepare analysis documents in advance and store the information for reference in every shipment to prevent issues such as returns or business losses.
Ensure all heavy metal tests in produce are conducted in laboratories accredited both domestically and internationally.
This helps growers and producers confidently verify the quality of their products.
1.Central Lab Thai
Central Lab Thai, accredited to international standards, provides testing services for all types of agricultural products, including cannabis, at reasonable prices. It covers the analysis of essential substances and residues in all categories. For specialized tests, additional analysis packages can be arranged upon request.
2. TISTR – Thailand Institute of Scientific and Technological Research (TISTR) and other scientific agencies.
The Center of Agricultural Innovation and Creativity (CIC) is a government scientific agency with laboratories offering residue and heavy metal analysis services for plants and agricultural products. These labs are distributed nationwide, providing fast testing queues and saving time. It is ideal for farmers or entrepreneurs who need preliminary checks or in-depth analysis.
3. Laboratories accredited with ISO/IEC 17025 standards or top universities in Thailand
Laboratories accredited with ISO/IEC 17025 standards are internationally recognized testing facilities, ideal for businesses seeking analysis results that can be used for export trade certification. For cannabis flower analysis, the laboratory must have a specific license for drug testing, as the extraction processes used during testing may involve substances that could be classified as controlled during the testing phase.KINGWHALE is committed to elevating the safety standards of its products for the future of consumers.
In an era where consumer safety comes first, King Whale (KINGWHALE) is dedicated to enhancing comprehensive agricultural production standards, from cultivation to processing. With a clear goal of delivering clean, safe products ready to compete in the global market.
We pay attention to every detail, especially heavy metal testing in every production lot to ensure that our products are free from toxic residues and are friendly to the health of consumers in the long run.
- Every batch must undergo analysis from a certified laboratory.
- Utilize controlled environment farming technology to precisely manage various factors.
- KINGWHALE products are ready to meet the demands of international markets with strict standards.
KINGWHALE firmly believes that “Good quality starts with responsibility at every process,” from raw material selection, production standard control, safety checks at every step, to delivering clean, standardized products to consumers.
We focus on every small detail that could affect the quality of all agricultural products, not only to ensure great yields but also to build confidence in the Thai agricultural industry, both domestically and internationally.
KINGWHALE strives to be a driving force in advancing the Thai agricultural industry with a transparent, safe approach that prioritizes consumer well-being. We are committed to building a strong production ecosystem and laying a sustainable foundation for farmers, producers, and consumers, ensuring a future where all sectors can grow together with quality.
