Restricted Entry and Pre-Harvest Intervals Explained

What Are REI and PHI?

Two of the most important numbers on every pesticide label are the Restricted Entry Interval (REI) and the Pre-Harvest Interval (PHI). Both are legally mandated waiting periods designed to protect human health. Violating either one can result in regulatory penalties, crop rejection, and most importantly, harm to workers and consumers.

The Restricted Entry Interval (REI) is the minimum number of hours after a pesticide application before workers can re-enter the treated area without full protective equipment. REI protects farmworkers from acute pesticide exposure through skin contact, inhalation, or accidental ingestion. REI values typically range from 4 hours for low-toxicity products to 48 hours or more for organophosphates and other higher-toxicity compounds.

The Pre-Harvest Interval (PHI) is the minimum number of days between the last pesticide application and when the crop can be harvested. PHI ensures that pesticide residues degrade to levels that meet food safety standards before the crop enters the food supply. PHI values range from 0 days (some biological products) to 60 days or more depending on the active ingredient and crop.

Why They Matter: Worker Safety and Food Safety

REI exists because pesticide residues on treated surfaces remain toxic for a period after application. Workers who enter treated fields during the REI can absorb pesticides through the skin (dermal exposure) or breathe in vapors and dried residue particles (inhalation exposure). Symptoms of acute exposure vary by product class but can include headaches, nausea, dizziness, and in severe cases, respiratory distress or neurological effects.

The EPA Worker Protection Standard (40 CFR Part 170) requires agricultural employers to inform workers about treated areas, post warning signs, and prevent entry during the REI. Workers who must perform emergency tasks during the REI must wear the full personal protective equipment (PPE) specified on the product label. Even with PPE, entry during the REI should be limited to situations where no alternative exists.

PHI protects consumers. Every country sets maximum residue limits (MRLs) for pesticides on food commodities. The PHI on the label is calculated to ensure that by harvest time, residues will be below the MRL. Harvesting before the PHI expires risks producing food with illegal residue levels. This can lead to shipment rejection, market losses, regulatory action, and damage to your operation's reputation.

Finding REI and PHI on Your Product Label

REI is typically listed in the Agricultural Use Requirements box near the beginning of the label. Look for phrases like "Do not enter or allow worker entry into treated areas during the restricted-entry interval (REI) of XX hours." The REI box is usually bordered and easy to find.

PHI is found in the Directions for Use section, typically listed under each specific crop. Look for phrases like "Do not apply within XX days of harvest" or "Pre-harvest interval: XX days." Some labels include a summary table listing PHI values for all registered crops, which makes it easy to find your crop quickly.

Important: A single product may have different PHI values for different crops. For example, a fungicide might have a 7-day PHI on strawberries but a 21-day PHI on grapes. Always check the PHI specific to your crop, not a generic value from a different crop section.

If you cannot find the REI or PHI on your label, or if the label is damaged, contact the manufacturer directly or look up the product on the EPA's Pesticide Product and Label System (PPLS). Never guess at interval values.

Tracking Compliance

Accurate record-keeping is essential for REI and PHI compliance. At minimum, record the following for every application:

• Product name and EPA registration number
• Date and time of application (not just the date — REI is in hours)
• REI in hours and the resulting safe re-entry date/time
• PHI in days and the resulting earliest harvest date
• Field or block treated
• Application rate and total product used

For REI tracking, calculate the exact time when the interval expires. If you applied at 2:00 PM with a 24-hour REI, workers cannot enter until 2:00 PM the next day. Post warning signs at all entrances to the treated area and remove them only after the REI has expired.

For PHI tracking, count forward from the application date. If you applied on March 15 with a 14-day PHI, the earliest harvest date is March 29. If you make multiple applications of the same product, the PHI countdown restarts with each application. The PHI is always counted from the last application date.

Common Intervals by Product Class

While you must always check the specific product label, the following ranges give a general idea of typical intervals by pesticide class. These are approximate ranges and should not be used for compliance decisions.

These ranges are for general education only. Always use the specific REI and PHI from your product label. Intervals can vary significantly between products within the same class.