Chlorpyrifos

MedEd Pesticide lists Chlorpyrifos as an insecticide in the organophosphate class.

MedEd Pesticide Summarizes Chlorpyrifos at a Glance

Type

Insecticide

Chemical class

Organophosphate

CAS number

2921-88-2

Formula

C9H11Cl3NO3PS

Molar mass

350.6 g/mol

EU status

Not approved as an active substance in the EU.

US status

Registered with EPA. 29 active products contain Chlorpyrifos.

MedEd Pesticide Summarizes Chlorpyrifos’s Toxicity Records

MedEd Pesticide holds 1,151 toxicity records for Chlorpyrifos, from 9 sources. The headline values are below.

Oral LD50 in ratsAcute, swallowed

Lowest reported 66 mg/kg, median 145 mg/kg, from 12 records.

Dermal LD50Acute, skin contact

Lowest reported 202 mg/kg, median 2000 mg/kg, from 4 records.

Lowest NOAELLong term, mammals

0.01 mg/kg-day in dog, 24 months. Source: ToxRefDB.

EPA signal wordsActive US products

Danger 0, Warning 13, Caution 16.

See all 1,151 Chlorpyrifos toxicity records in the explorer. The records come from EPA’s Toxicity Values Database, and the methodology explains their limits.

MedEd Pesticide Reports Chlorpyrifos’s EU Safety Reference Values

MedEd Pesticide finds no safety reference values for Chlorpyrifos in the EU database.

MedEd Pesticide Lists Chlorpyrifos’s EU Hazard Classification

MedEd Pesticide lists the harmonised EU hazard statements for Chlorpyrifos below.

• H301 Toxic if swallowed
• H400 Very toxic to aquatic life
• H410 Very toxic to aquatic life with long-lasting effects

MedEd Pesticide takes EU status, reference values and hazard classification from the EU Pesticides Database. MedEd Pesticide takes US status from EPA’s Pesticide Product Information System (dated 2026-10-13) and chemical identity from PubChem. Retrieved 2026-10-16. Values and approvals change, so check the source for the current entry. See the methodology and the glossary, or compare Chlorpyrifos with another pesticide.

MedEd Pesticide. (2026). Chlorpyrifos. https://mededpesticide.org/pesticides/chlorpyrifos/ (accessed Month Day, Year)