What pesticide residue analysis measures (pesticide and herbicide residue)
FDA's multiresidue methods are capable of simultaneously determining many different pesticide chemical residues. Selective residue methods are sometimes needed to analyze pesticides that the multiresidue methods do not adequately detect.
In its regulatory monitoring program, FDA selectively tests imported and domestic commodities, such as raw fruits and vegetables, for approximately 800 pesticide residues.
EPA calls the small amounts of pesticide that remain in or on fruits, vegetables, grains and other foods residues.
Ask the laboratory which of the residues you care about its proposed method covers, and whether a selective method is needed in addition. Give it the commodity, the product and ingredient history, and the chemicals of interest, and get the analyte list before you commission the test.
Pesticide residue analysis in vegetables
FDA's regulatory monitoring covers raw fruits and vegetables among its commodity examples. EPA's tolerances apply to the same group of foods: fruits, vegetables, grains and other foods.
Before you ask for a panel, write down the crop, lot, destination and treatment history. Ask the laboratory for its sampling instructions and its list of residues, and do not assume that a general screen name covers your case.
Tolerance: the limit a result is compared with
A tolerance is the maximum residue level of a specific pesticide chemical permitted in or on a specific human or animal food in the United States. The tolerance is the residue level that triggers enforcement: a commodity with residues above it is subject to seizure by the government.
When EPA sets a tolerance, it considers the toxicity of the pesticide and its break-down products, how much is applied and how often, how much remains on the food by the time it is marketed and prepared, and all possible routes of exposure.
Some pesticides are exempted from the requirement to have a tolerance. When new data raise safety concerns about specific uses of a pesticide, EPA may lower or revoke the tolerance altogether.
The tolerance applies to food imported into the United States as well as to food grown here.
Check two things: the concentration, and whether a tolerance or exemption exists for that pesticide on that commodity. Look up the current provision for the chemical and commodity rather than a historical summary, and keep the rule date and commodity description with your comparison. Name the chemical and the exact commodity, not the trade name of the product.
Over-tolerance and no-tolerance violations
An over-tolerance violation means pesticide chemical residues are detected at a level above a tolerance. A no-tolerance violation means a residue is detected in a commodity for which EPA has not established a tolerance or an exemption from the need for a tolerance.
For import shipments containing violative pesticides, FDA may refuse entry into US commerce. The responsible firm and product may be placed on an import alert under "Detention Without Physical Examination," which can be invoked for future shipments of that firm's commodity based on the finding of a single violative shipment.
If you receive an official notice, check which kind of violation it describes and keep that wording in your reply. For an export lot, the US rules are only one reference: ask the buyer and the destination country's authority for their own criteria and compare the result with those separately.
Which agency enforces tolerances
FDA enforces EPA tolerances for domestic foods shipped in interstate commerce and foods offered for import, except for meat, poultry, catfish (Siluriformes) and certain egg products, which USDA's Food Safety and Inspection Service regulates. State enforcement agencies also check foods produced in this country, and USDA tests meat and milk.
When you have a residue question, decide first which agency covers the commodity: meat, poultry, catfish and certain egg products go to FSIS, other foods to FDA. Do not apply a fruit or vegetable monitoring summary to an animal-food product.
Monitoring data: Pesticide Data Program and Total Diet Study
The USDA Pesticide Data Program is a national pesticide residue monitoring program. It samples, tests and reports pesticide residues on agricultural commodities in the US food supply, with an emphasis on commodities highly consumed by infants and children, in cooperation with State agriculture departments and other Federal agencies.
PDP data enable EPA to assess dietary exposure, facilitate the global marketing of U.S. agricultural products and provide guidance for FDA and other governmental agencies.
FDA's Total Diet Study monitors pesticide chemical residue levels in table-ready foods representative of the US diet. It is distinct from FDA's regulatory pesticide residue monitoring program and focuses on information gathering rather than enforcement.
If you show a monitoring chart to a buyer, name its program, period, commodity and source. Without those, a national observation can look like a result for your shipment, which that program never sampled.
Keep your spray records in one place. Free to start.
Phytosanitary certificate: a separate export document
APHIS provides plant health inspection and certification for plants and plant products shipped to foreign countries. Importing countries require these certificates, which attest that products are pest- and disease-free.
A phytosanitary certificate certifies that a plant or plant product has been inspected per appropriate procedures and conforms to the current phytosanitary regulations of the importing country.
A phytosanitary certificate for reexport applies to foreign-origin plants or plant products that entered the United States with a valid phytosanitary certificate. It certifies that the product is considered to conform to the importing country's regulations based on the original foreign certificate, an additional inspection, or both, and has not been subjected to the risk of infestation during storage.
APHIS directs exporters to contact their State's export certification specialist first, then to work with an authorized certification official, who helps apply for the certificate through PCIT. User fees apply and vary with the authority conducting the inspection and issuing the certificate.
Keep the phytosanitary certificate in the shipment file next to the chemical residue report, and remember they come from different processes: a laboratory analyst writes the residue report, an authorized certification official decides on the certificate.
Soil and water residues
Pesticides in soil may be taken up by plant roots and moved to other plant tissues, including the fruit.
The type of soil and the type of pesticide can affect pesticide persistence. Pesticides applied to sandy or coarse-grained soils are more likely to leach through the soil and contaminate groundwater.
Do not apply a soil or water result to a harvested lot: pesticide in soil is not by itself evidence that the food is over a tolerance, and food, soil and water each need their own sampling and reading.
Half-life
A half-life is the time it takes for a certain amount of a pesticide to be reduced by half. After one half-life 50% of the original amount remains, after two 25%, and after three about 12%.
Each pesticide can have many half-lives depending on conditions in the environment. For permethrin, the soil half-life is about 40 days (range 11-113 days), and in the water column it is 19-27 hours.
Sunlight, temperature, the presence of oxygen, soil type, how acidic the soil or water is, and microbe activity all affect how long a pesticide remains in the environment. Half-lives are commonly reported as time ranges because environmental conditions change over time.
Half-life values group into low (less than 16 days), moderate (16 to 59 days) and high (over 60 days) persistence.
How pesticides break down and move
Radiation from the sun breaks certain chemical bonds. Bacteria and fungi can break down chemicals. Water breaks chemicals apart into pieces that dissolve better in water (hydrolysis), which is typically a very slow process. Plants and animals can change chemicals into forms that dissolve better in water (metabolites).
Chemicals that stick tightly to particles can become inaccessible or move away with those particles (sorption). Some chemicals are absorbed by plants or animals from soil, water, food and air, and accumulate when the organism is exposed again before it can remove them (bioaccumulation).
When a pesticide breaks down it forms new chemicals that may be more or less toxic than the original chemical. A pesticide product's formulation can also change how the active ingredient behaves in the environment, and the properties of the formulation may dominate initially.
Half-lives are often determined in a laboratory, where conditions like temperature are controlled and soil, water or plant material mixed with a known amount of pesticide is sampled over time. Field studies expose the pesticide to outdoor conditions, and their half-life values can vary greatly with the exact conditions.
Before commissioning a soil or water test, ask the laboratory which parent chemicals and which breakdown products its method measures, because a lower parent-compound result alone can mislead when new chemicals form. Write down the sampled medium and location (sediment, water, plant or animal tissue), so a reviewer can tell the results apart.
Keep the full product name, including the formulation, with the treatment history, and note any earlier use of the same active ingredient in a different formulation. When you use a published half-life, note whether it came from a laboratory or a field study. Treat a half-life as background about the environment, not as a countdown to a clean lot.
Next step
Send the laboratory the commodity, destination, lot and treatment history, and ask for its list of residues. Check the applicable tolerance against that list. Product labels and registration records are covered in how to read a pesticide label and the EPA product lookup.