Environmental History

Harold J. Farber, MD, MSPH, FAAP

Introduction

•Respiratory irritants, toxins, and allergens may all contribute to a child’s breathing problems.

•Problems can arise from indoor and outdoor sources; however, indoor exposures contribute most to respiratory symptoms in children.

•Exposures can occur in the home, at school, at day care, at play, or at work.

Types of Environmental Exposures

•Irritants stimulate airway inflammation by a mechanism of action not dependent on prior sensitization.

•Toxins directly cause damage to airway or lung tissues.

•Allergens

—Airway inflammation is stimulated by an allergic reaction.

—Mast cells, eosinophils, and immunoglobulin E (IgE) play important roles in allergic reactions.

—The individual needs to have been previously sensitized (ie, allergic) for exposure to the allergen to be a problem. Seasonal allergies are uncommon prior to the second year after birth.

—Relevant allergens are usually inhaled. It is unusual for a food allergy to cause only respiratory symptoms.

•Hypersensitivity pneumonitis

—Organic and inorganic antigens can trigger a T cell–mediated reaction in sensitized persons.

—Acute and subacute hypersensitivity pneumonitis can mimic pneumonia.

—Chronic hypersensitivity pneumonitis can lead to pulmonary fibrosis and severe lung disease.

—Implicated antigens include avian (bird) antigens, fungi and fungal spores, bacterial antigens, and low–molecular-weight chemicals.

—This type of reaction is uncommon; however, it is important to recognize.

•The most important part of identifying an environmental contribution to a child’s respiratory illness is the history of relevant exposures.

•The patient or parent may not connect the relevant exposure to the respiratory symptom.

•Often it is not 1 exposure exclusively that contributes to the respiratory symptoms but a combination of several.

Respiratory Irritants and Toxins

Respiratory irritants and toxins can be a problem for anyone with respiratory symptoms. Previous sensitization is not needed.

Common Indoor Respiratory Irritants and Toxins

•Smoke from any source

—Common sources of smoke include tobacco, other substances of abuse, incense, fireplaces, wood-burning stoves, barbecue grills, gas stoves, gas heaters, and kerosene heaters.

—Sometimes the source of smoke may be from a friend or neighbor. Smoking in multi-unit housing involuntarily introduces smoke exposure to those who live in proximity to smokers.

—Although not technically smoke from combustion, the emissions from electronic nicotine delivery systems (ENDS) contain chemicals that are known respiratory irritants and toxins.

•Strong chemicals

—These include air fresheners, cleaning agents, and insecticides.

—Chemicals used in hobbies or home remodeling can be irritants or a source of toxic exposures.

—Ask about exposure to formaldehyde due to off-gassing from building materials, household products (glues, paints, finishes, etc), and products of combustion (from gas stoves, kerosene space heaters, tobacco smoke, etc).

Common Outdoor Respiratory Irritants and Toxins

•Air pollution worsens asthma problems. Important effects on lung function have been demonstrated for ozone, fine particulate matter, oxides of nitrogen, volatile organic compounds, and diesel smoke.

Allergens

•Allergens are only a problem for an individual who has been sensitized to them.

•Symptoms may be difficult to associate with the exposure if the exposure is continuous, such as in the home.

•Late-phase allergic reactions can occur 8–12 hours after exposure, creating further challenges in identifying the relevant exposure.

Common Indoor Respiratory Allergens

•House dust mites

—House dust mites thrive on humidity and shed skin, both of which are in ample supply in the bed and bedding.

—Dust mites also thrive in the fabric of carpets and upholstered furniture.

—Dust mites do not grow well in areas of low humidity (<40%).