What is phosphine?

Phosphine is a colorless gas with a fishy or garlicky odor released when aluminum phosphide pellets, which are used as a pesticide, come into contact with moisture.

Who can use aluminum phosphide?

To purchase or apply the restricted use pesticide, users must be certified applicators and have a specialized license for fumigation, which requires extensive training and passage of a written exam.

How could a person be exposed to phosphine?

Inhalation is the most likely way. Workers handling the product might be exposed and people who live near where it's being used might inhale it.

How does phosphine affect health?

Exposure to phosphine can cause abdominal pain, nausea and vomiting. High levels can cause weakness, bronchitis, excess fluid in the lungs, shortness of breath, convulsions and death.

Who sets the requirements for using aluminum phosphide?

The federal government sets minimum requirements for use of the substance, which are listed on a lengthy product label. Applicators are required to follow this Environmental Protection Agency label, which includes precautions and specific use instructions. States can set more stringent standards but cannot lower the label standards.

The label on Fumatoxin, the brand identified as the one used at the Layton home, specifies that it cannot be used within 15 feet of an inhabited structure. Fumatoxin can be used to control voles, according to the label.

Sources: Agency for Toxic Substances and Disease Registry and Greg Baumann, vice president and senior scientist for the National Pest Management Association.