What is a characteristic of teratogens? 

A)  They are harmful because they are irritating to skin or lungs. 
B)  They cause birth defects. 
C)  They cause mutations. 
D)  They are fatal to humans in low doses.

Teratogens

Agents or factors that can cause the development of physical defects in an embryo or fetus during pregnancy.

Birth Defects

Birth defects are physical or biochemical abnormalities present at birth that can result in physical, mental, or emotional disability or dysfunction.

Mutations

Changes in the DNA sequence of a cell's genome, which can lead to variations in the traits of an organism, and are a primary source of genetic diversity.