# Toxic substances with LD50 oral toxicity greater than 5 mg/kg but no more than 50 mg/kg — Postal shipping restrictions by item category

For Toxic substances with LD50 oral toxicity greater than 5 mg/kg but no more than 50 mg/kg, carrier is USPS; restriction type is restricted; scope is domestic mail; conditions is Mailable only when sent between authorized parties (manufacturers, dealers, bona fide research labs, or government employees for official use); for domestic air a Shipper's Declaration for Dangerous Goods is required, recorded from its source on 2026-08-04.

- **Item category:** Toxic substances with LD50 oral toxicity greater than 5 mg/kg but no more than 50 mg/kg
- **Carrier:** USPS _(our reading, not quoted from the source)_
- **Restriction type:** restricted _(our reading, not quoted from the source)_
- **Scope:** domestic mail _(our reading, not quoted from the source)_
- **Conditions:** Mailable only when sent between authorized parties (manufacturers, dealers, bona fide research labs, or government employees for official use); for domestic air a Shipper's Declaration for Dangerous Goods is required _(unconfirmed — we could not tie this to the quote below)_

## What the source says

> Toxic Substances with LD 50 Oral Toxicity of 50 mg/kg or Less: Division 6.1 toxic substances having LD 50 for oral toxicity greater than 5 mg/kg but less than or equal to 50 mg/kg are mailable only when sent between authorized parties under specified conditions

## Source

- https://pe.usps.com/text/pub52/pub52c3_025.htm

Last verified: 2026-08-04. Review by: 2027-08-04.
Part of [Postal shipping restrictions by item category](https://referencesource.org/shipping-restrictions-by-class/).