Does fresh thyme have heavy metals? A complete guide

November 18, 2025 •

4 min read

Recent studies have detected concerning levels of heavy metals like lead and cadmium in various store-bought herbs and spices, including thyme, raising questions about food safety. This issue is particularly relevant for those who cook with or consume fresh thyme regularly.

Quick Summary

This guide explains the process of heavy metal absorption in plants, highlights the risks associated with contaminated thyme, and provides practical advice for minimizing exposure, including sourcing and growing methods.

Key Points

Thyme can contain heavy metals: Studies, including research by Consumer Reports, have found heavy metals like lead, cadmium, and arsenic in fresh and dried thyme products.
Contamination sources vary: Heavy metals enter thyme through contaminated soil, polluted water, or during the manufacturing process.
Growing your own is safest: Cultivating fresh thyme at home with clean soil and water is the most reliable method to minimize heavy metal exposure.
High-risk heavy metals identified: Lead, in particular, has been found in concerning levels in some fresh thyme samples, sometimes exceeding international standards.
Sourcing matters for store-bought thyme: Consumers should choose transparent brands that detail their sourcing and testing procedures to ensure food safety.
Consider overall exposure: While small amounts are not highly dangerous, regular consumption of contaminated herbs contributes to total heavy metal intake, which can pose health risks over time.

Sources of heavy metal contamination in herbs

Heavy metals can be absorbed by plants, including thyme, from their environment. This absorption occurs primarily through the soil and water where the plants are grown.

Industrial and environmental pollution

Industrial activity, vehicle emissions, and agricultural practices involving pesticides and fertilizers can all introduce heavy metals into the soil and water supply. As the thyme plant grows, its roots can take up these metals, which then accumulate in its tissues. Even organically grown herbs are not immune to this, as they are susceptible to environmental contamination.

Post-harvest processing and storage

Contamination is not limited to the growing phase. Heavy metals can also be introduced during manufacturing and processing. This can occur from contaminated equipment, improper storage, or in some cases, the intentional addition of toxic metals to enhance color, particularly in products sourced from less-regulated regions.

The specific risks of heavy metals in thyme

Studies have singled out thyme and oregano as particularly problematic, with some tests finding heavy metals in almost all brands.

Lead (Pb): Research in the UAE found fresh thyme herbs with lead concentrations of 0.718 mg/kg, exceeding international standards. The World Health Organization (WHO) has also reported permissible limits for lead in herbal materials, which are often exceeded in real-world testing.
Cadmium (Cd): While some studies have found cadmium levels in thyme below permissible limits, others report concentrations over the FAO/WHO standards. Cadmium exposure poses health risks due to its long half-life and accumulation in organs.
Arsenic (As) and Mercury (Hg): Elevated levels of arsenic and mercury have also been detected in thyme products, although in some cases, fresh herbs might have lower concentrations than dried varieties or teas.

Reducing your risk of heavy metal exposure from thyme

While the prospect of contaminants is worrying, there are actionable steps consumers can take to minimize their risk. The first step is to be an informed buyer and, when possible, a conscientious grower.

Strategies for consumers

Source from reputable brands: Look for companies that have strong heavy metal testing protocols and make their results public. While brand name is not a guarantee of safety, some companies are more transparent than others.
Look for lower-risk alternatives: Consumer Reports found some herbs and spices, such as black pepper and coriander, generally had lower heavy metal levels. Diversifying your spice rack can help reduce overall exposure.
Consider total dietary exposure: Experts recommend considering your total intake from all food sources. The occasional use of a contaminated herb is less risky than regular consumption, especially for sensitive groups like children.

Growing your own herbs

Growing your own fresh thyme is one of the most effective ways to control its quality and reduce heavy metal exposure.

A checklist for home growers

Use high-quality soil: Start with new, tested potting mix instead of relying on garden soil that might have decades of accumulated contaminants.
Ensure clean water: Use filtered water for irrigation. Well water, in particular, should be tested for contaminants like lead and arsenic.
Choose a safe location: If growing outdoors, avoid placing your herb garden near busy roads or industrial areas where airborne pollutants can settle on the plants.
Monitor environmental factors: Be aware of your local environment. Runoff from old buildings or nearby industries can affect soil and water quality over time.

Comparison of thyme options


Feature	Commercial Fresh Thyme	Homegrown Fresh Thyme	Dried/Processed Thyme Products
Control over Contamination	Very Low	Very High	Low
Source Transparency	Varies by Brand	Full Transparency	Low to Moderate
Risk of Heavy Metals	Medium to High	Very Low (with proper care)	High, especially in teas and blends
Cost	Regular purchase expense	Initial investment for seeds and soil	Varies, often cheaper per serving
Environmental Factors	Unknown growth conditions	Full control over soil and water	Unknown until testing is done
Processing Risks	Minimal post-harvest handling	No post-harvest processing issues	Can be contaminated during drying or grinding

Regulation and industry response

While regulatory bodies like the European Food Safety Authority (EFSA) and World Health Organization (WHO) set maximum permissible limits for heavy metals in food and herbal products, monitoring and enforcement can be challenging. The American Spice Trade Association acknowledges the difficulty in eliminating all heavy metals from herbs but provides guidance to suppliers. Some jurisdictions, like New York State, have implemented specific limits for heavy metals in spices following recalls.

Conclusion: Safe consumption and future considerations

Yes, fresh thyme can have heavy metals, but the risk is not insurmountable. The level of contamination is highly dependent on the plant's growing environment and post-harvest handling. For regular consumers, especially those with increased vulnerability, taking steps to reduce exposure is prudent. Growing your own fresh thyme using clean water and quality soil is the most effective way to guarantee its safety. For those purchasing fresh or dried thyme, sourcing from transparent companies with rigorous testing protocols is the best approach. Ultimately, awareness and responsible sourcing can ensure that this flavorful herb remains a healthy addition to your diet.

Frequently Asked Questions

Yes, organic fresh thyme can still be contaminated with heavy metals. The 'organic' label pertains to farming practices (e.g., avoiding synthetic pesticides), but it does not guarantee protection against environmental pollutants in the soil or water.

Not necessarily. Contamination levels depend more on the growing environment than on whether the herb is fresh or dried. However, some studies have found higher concentrations in dried products, and additional contamination can occur during processing and storage.

Thyme plants absorb heavy metals primarily through their roots from contaminated soil and polluted irrigation water. Sources of contamination include industrial waste, vehicular emissions, and certain pesticides or fertilizers.

While the occasional small amount is not typically cause for alarm, frequent exposure to even low levels of heavy metals can accumulate in the body over time and pose health risks, particularly for vulnerable populations.

Studies have most frequently detected lead (Pb), cadmium (Cd), and arsenic (As) in thyme. Some research also points to the presence of mercury (Hg).

Washing fresh thyme can help remove surface dirt and some residue, but it will not remove heavy metals that have been absorbed into the plant's internal tissues. The metals are taken up by the roots and become part of the plant itself.

Heavy metal exposure can cause a variety of health issues. Long-term exposure to lead can damage the nervous system, while cadmium can cause kidney damage. These metals are non-biodegradable and accumulate in the body over time.

To reduce exposure, purchase herbs and spices from trusted sources known for robust testing. Diversify your herb usage rather than relying on just a few types, and consider your total dietary intake from all sources.