Product Contamination: Dangers & How to Avoid Contaminants in Cannabis

In a study of black market cannabis in Spain, nearly 90% of the cannabis samples collected tested positive for E.coli. In a review by the National Institute of Health, up to 50% of liquid samples tested showed levels of detectable lead. These are not rare occurrences and represent just two examples of cross contamination.

Many cannabis companies are discovering that cross contamination is a huge risk no matter how careful they are. In the case of hemp and cannabis, cross contamination refers to the presence of harmful organisms that have been transported from one source to another through a carrier. It can occur as early as the pre-harvest stage all the way through to harvest and post production.

The most common types of cross contamination are microbial but also include mold, metals, and pesticides. Lesser known contaminants, like pollen and non-cannabis additives are also risk factors for cross contamination.

So why is hemp at such a high risk for cross contamination what are all the different methods by which it can occur? More importantly, what can you do to prevent cross contamination?

In this post:

  • Cannabis contamination risk
  • Soil contamination & prevention
  • Cross pollination contamination & prevention
  • Mold outbreak contamination & prevention
  • Dirty equipment & hands contamination
  • Non cannabis terpenes contamination
  • Why test for contaminants
  • Contamination during sample collection
  • Working with a trusted laboratory

The Risk Factor

Cross contamination of crops is a huge issue that affects cannabis more than most plants. The reason is that cannabis is a bioaccumulator, which means it can easily take in pesticides, heavy metals and toxins from the air and soil. This is an even bigger issue if you grow outdoors due to the environmental elements beyond your control.

But that doesnt mean indoor plants are immune from cross contamination either. Indoor plants are no strangers to cross contamination through equipment, but this is an even bigger issue in outdoor grows due to environmental elements you may have not considered.

Soil Cross Contamination

If you or your neighbor’s soil has been heavily treated with chemical pesticides, your crops are at risk for cross contamination. For example, if you’re a Florida grower, you may be located next to a citrus farm which can sustain higher levels of pesticides than hemp. The problem is that these pesticides can seep into groundwater, which can carry the chemicals from your neighbor’s farm to yours.

That means despite your efforts to grow organic crops or use safe levels of pesticides, your crop may still become contaminated. You may experience a similar issue if you recently purchased your farm. In this case, you may not know what pesticides the person before you was using.

For example, if the previous farmer grew cotton or soybeans, they probably sprayed the soil with heavy doses of pesticides. At high enough levels, these pesticides may remain in the soil long after they were originally sprayed.


If you’re in the market for a new plot of land, the best method of prevention is to do your due diligence before you purchase. Find out who your neighbors are and who your potential seller is. Then ask what they grow and what pesticides they may use.

To help prevent contaminated groundwater from reaching your plant, you may also consider growing vegetative buffer plants which can act as a barrier.  Regardless of your method of prevention, make sure to submit a sample to an accredited laboratory for a soil analysis.

At ACS Laboratory we test soil for trace elements of pesticides as well as all potential contaminants and even micronutrients so you know exactly what you’re getting. If you currently own a plot of land, you’ll still want to test your soil before you plant to help guarantee that your end product is safe for use.

Cross Pollination

If you’re growing CBD hemp or cannabis, you want female-only plants to increase your yield and cannabinoid potency. More specifically, you want virgin unpollinated female plants. However, your pesky neighbor may be growing industrial hemp, which means his or her plot contains male plants as well.

Male cannabis plants can produce hundreds of thousands of pollen grains, which can be carried great distances through the wind and pollinate your females. While cross pollination is one of the more rare cases of contamination, it is still a risk factor you should be aware of. A strong gust of wind can carry pollen over to your field and pollinate your female plants, which will lead to fruiting instead of flowering.

That means a gust of wind can be the deal breaker that compromises your entire yield.


Similar to soil contamination, the best way to prevent cross pollination is to check out your neighborhood before buying a plot. If it’s too late for that, your best options may be to build a protected grow house or consider moving your operation to a different location. Vegetative buffers could also prevent cross pollination by making a barrier.

Mold Outbreak

Mold can grow on almost any substance where moisture is present, which means that you and your neighbor’s plants are at risk for developing this fungal contamination. Mold reproduces by spores that can easily travel through the air with the right gust of wind and attach to your skin or your plants. The damage can cause slight odor, spoilage or significant illness to the end user if left unchecked.

This a huge threat especially in humid Florida where common mold outbreaks can destroy an entire crop. Not only is your plant at risk for mold during the growth phase, it can also develop this fungus during drying and curing phases. In fact a large percentage of mold begins after harvest, as a result of poor air quality and high moisture levels.

As long as the buds have at least 12.5% moisture content, they are at risk for developing mold. Moreover, if your hands or machinery are contaminated with spores, you can easily cross contaminate your crop during any phase of the harvest process.


To help prevent cross contamination of your outdoor crops, consider growing vegetative buffers to prevent mold spores from reaching your crop. They also have the benefit of protecting your plants from other contaminants such as pollen and pests. If growing indoors, you must completely sanitize your space to kill all microbes before you start.

While this will prevent most issues, unfortunately traditional cleaning methods may not prevent all airborne spores that exist in small cracks, for example. That means you’ll have to be diligent and consistently monitor your crop for signs of mold so you can catch the spores before they spread. You must also make sure there is always proper ventilation.

During the drying phase, the best method of prevention is to monitor moisture levels and carefully handle the plant with clean hands and equipment. Additionally, you must set up drying racks with proper spacing to ensure that each plant receives the ventilation it needs to dry. To confirm that your plant contains safe levels of moisture, we recommend that you send samples to a laboratory like ACS to test.

Within 3-5 days, we’ll let you know exactly how much water and moisture your sample contains so that you can prevent mold from growing. Later after the drying phase, you’ll want to confirm that your final product is safe by testing for mold, mildew and other microbial pathogens.

Dirty Equipment & Hands

Unsanitized equipment and handling can easily cause detrimental cross contamination in the form of mold, bacteria and even heavy metals from old equipment. This type of contamination can either destroy your crop or become a major health threat if your final product is compromised. This can occur at your farm during every phase of the growth process but unfortunately the risk doesn’t end at your facility.

Cross contamination may also happen at the processing facility that you send your hemp or cannabis to. For example, your hemp may become contaminated if a processing facility handles another crop like tobacco and doesn’t properly clean the equipment before processing your product.


Wash your hands: This is the most basic and effective strategy to prevent cross contamination at your farm or facility. Wash your hands before and after handling the plant, as well as between batches. Moreover you want to establish a formal hand washing policy to ensure that everyone at your facility is maintaining strict hygienic standards.

Establish equipment, surfaces and storage cleaning protocols: Make sure to store different batches in separate containers and don’t use the same equipment to process them, unless you sanitize them first. Make sure all countertops are clean at all times using effective methods to eliminate pathogens. Test, test, test: Take proactive steps to test your samples early and throughout the product development process.

The earlier you test samples and catch potential issues, the better chances you have to remediate the problem before it spreads to the final production phase.

Non-Cannabis Terpenes

One of the most interesting cases of cross contamination that we’ve seen at ACS Laboratory occurred when one of our customers’ products tested positive for pesticides. At first, we couldn’t figure out why because their cannabis plants were 100% clean. But we conducted a thorough R&D investigation, and discovered that the source of contamination was non-cannabis citrus dried terpenes that were infused in the product.

Unknowingly, this customer had received contaminated terpenes from a local supplier which caused the final product to fail the safety test. Based on this discovery, the customer was able to mitigate the problem by seeking an alternative supplier.


If you’re using non-cannabis terpenes or any other natural additives in your final hemp or cannabis product, the best method of prevention is testing the compounds before you process them. Even if you trust your supplier, the only way to be sure that all ingredients are clean is to order an analysis through an accredited laboratory like ACS.

Why You Need to Test

When it comes to cross contamination, ignorance is not bliss. It can only lead to the destruction of your entire crop or unsafe and non-compliant finished product. That’s why you need to test early and often to be sure that your product is viable.

Before you plant, send your soil to a laboratory like ACS for testing. At ACS we conduct a comprehensive analysis of micronutrients pesticides and heavy metals to ensure your soil is suitable for growth. We can test for 70 pesticides, including glyphosate, which is found in the weed killer Roundup.

Moreover, we test for 4 heavy metals, and dozens of microbial pathogens in soil, plant and finished products. We will ensure that your final product is safe and compliant with all federal and state regulations. Check out our hemp testing timeline blog for more information.

Cross Contamination Risk When Collecting Samples

Unfortunately cross contamination can also occur during the process of collecting samples to send for testing. To prevent this risk, make sure to wash your hands and vacuum seal all samples to prevent moisture buildup. Then, schedule a test with ACS Laboratory.

If you live in Florida, you can also request a courier service. We’ll pick up your samples and transport them in a temperature controlled van to ensure they remain uncompromised.

The Importance of a Trusted Laboratory

Cross contamination doesn’t just happen in the ground or from improper sampling procedures. Unqualified or otherwise negligent laboratories can also cross contaminate your samples, leading to fallacious results. This type of contamination can occur from dirty equipment, a staff member who does not wash his or her hands, or due to a non-sterile environment.

The fact is that not all labs are made equal.

ACS Laboratory

At ACS, we have 10+ years of experience conducting medical grade clinical testing. We are the largest laboratory in the Southeast and we are ISO Accredited, DEA registered and CLIA certified. We utilize medical sterilization techniques and disposable instruments to eliminate any chance of cross contamination between tests.

We also have standard operating procedures in place to sterilize and calibrate machinery. Additionally, our technicians always wear lab coats, gloves, goggles and protective equipment because your product’s integrity is our highest priority.  

We’ve won 21 Emerald Test Badges for precision in testing, which include screenings for pesticides, mycotoxins, STEC, salmonella, aspergillus mold, heavy metals, and water activity. Our results and experience sets us apart and we’re proud to help cannabis companies in the pursuit to sell high quality products.

The Cannabinoids Guide

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