Aaron is 5 years old. what does the u. s. department of health and human services consider to be the most hazardous to his health?

The most hazardous to his health is lead poisoning. It is because Aaron is still young and he doesn't know mostly all of the things around him and the things that which is bad and good for him. Considering he is a child, he is likely exposed to materials such as toys and he would not know that some of these toys are contaminated with hazardous materials that could contribute to lead poisoning.