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The body’s developmental period begins at pregnancy when a sperm fertilizes an egg. The developmental period continues through birth and ends at the time of sexual maturity. This maturity involves the formation and change of the body’s organs and tissues.

The respiratory system starts with the nose, nasal cavities, paranasal sinuses, nasopharynx, and larynx. It continues with a conducting segment (trachea and bronchi) that enters the lungs. transitional segment made up of respiratory bronchioles and primary, secondary, and tertiary bronchioles moves air deep into the lungs.

Warfare or terrorism agents are a class that includes chemicals, biological substances, radioactive materials, nuclear materials, or explosives. These agents can be used in war against enemies or to frighten groups of individuals.

Hydrocarbons are a class of chemicals that contain only hydrogen and carbon atoms. Some have hydrogen with rings of carbon atoms, called polycyclic aromatic hydrocarbons or PAHs. Hydrocarbons with additives, such as gasoline, also are included.

Nitrosamines are a group of organic chemicals formed by the interaction of nitrites with amines or amides inside the body; they have been found to cause cancer in animals. Ethers contain hydrocarbon groups connected by an oxygen atom. They are volatile and highly flammable organic compounds, and ; some have been used as anesthetics.

Inorganic substances are a group of chemicals that contain no carbon. Examples include ammonia, hydrogen sulfide, all metals, and most elements (such as calcium).

Emergency Responders

The Steps program, formerly known as Steps to a HealthierUS, was the first Centers for Disease Control and Prevention (CDC) program to support a community-based, integrated approach to chronic disease prevention. Steps interventions addressed both diseases and risk factors, focusing on the 3 leading causes of preventable deaths in the United States — tobacco use, poor nutrition, and physical inactivity — and the associated chronic conditions of asthma, diabetes, and obesity.

Persons using assistive technology might not be able to fully access information in this file. For assistance, please send e-mail to: mmwrq@cdc.gov.

Persons using assistive technology might not be able to fully access information in this file. For assistance, please send e-mail to: mmwrq@cdc.gov.