A Casual Talk on Pesticide Residues

Crops are attacked by diseases and pests during natural growth, so chemical pesticides are often applied to secure yields.

As chemical agents used to prevent and control plant diseases and pests, pesticides are key production inputs. Without them — or if humanity stopped using them — the world would face a food crisis. News about pesticide‑related suicides or “toxic long beans” has led many consumers to equate pesticides with poison and to panic at the mention of residues. In reality, there are thousands of pesticide types: highly toxic, low‑toxic, and even non‑toxic. With advances in fine chemicals and stronger environmental/health standards, highly toxic products are being phased out, and even low‑toxic ones are strictly regulated. The R&D, trials, and approval of new pesticides are lengthy — not unlike pharmaceuticals — to ensure maximum efficacy with minimal harm once on the market.

Toxicity and efficacy are different concepts. Efficacy refers to the effect on the target; when we say a pesticide works well, we mean it suppresses or kills the pest effectively. Toxicity refers to the impact on non‑targets (bees, birds, fish, humans, etc.).

Toxicity depends on dose. Only when the dose reaches a certain level do acute or chronic toxic effects occur. Talking about toxicity without considering dose is misleading. Toxicity levels for non‑target organisms are established through rigorous toxicology experiments. Regulators then set maximum residue limits (MRLs) in food based on mammalian toxicity. Residues are quantities; each pesticide has its own MRL. As long as residues in a food are below the official MRL, the food is considered compliant and safe.

Residue levels are measured with chromatography, immunochromatography, Raman spectroscopy, and other methods. If the measured level exceeds the standard, we say the residue is over the limit; if below, it is compliant and the food is safe. Food safety does not mean “zero pesticide,” often it just means “below the detection limit.” There are thousands of pesticides — we cannot test for every possible one in every food. In practice, ingesting some residues is nearly unavoidable; consumers should accept this reality 😂.

Still, we can take simple steps to reduce potential intake:

• Crops that easily get sick or attract pests are usually sprayed more — eat less of them (e.g., chives, strawberries).
• If you can’t abstain, wash well. Soak fruits and vegetables in warm water for a longer time and rinse to remove surface residues.
• Peel when possible (e.g., grapes).
• Buy in season. At lower temperatures, pests are less active and spraying is lighter; for example, pre‑Qingming tea is typically safer than pre‑rain tea.
• Eat less of vegetables that adsorb pesticides strongly (e.g., celery).
• When brewing tea, discard the first infusion.
• Finally: avoid large one‑time intakes. If a particular batch exceeds the MRL and you eat one or two pieces, risk is small; eat a lot, and cumulative exposure can become a problem.

Published at: Apr 23, 2019 · Modified at: Dec 11, 2025