Introduction

Indoor air pollution poses many challenges to the health professional. This booklet offers an overview of those challenges, focusing on acute conditions, with patterns that point to particular agents and suggestions for appropriate remedial action.

The individual presenting with environmentally associated symptoms is apt to have been exposed to airborne substances originating not outdoors, but indoors. Studies from the United States and Europe show that persons in industrialized nations spend more than 90 percent of their time indoors¹. For infants, the elderly, persons with chronic diseases, and most urban residents of any age, the proportion is probably higher. In addition, the concentrations of many pollutants indoors exceed those outdoors. The locations of highest concern are those involving prolonged, continuing exposure - that is, the home, school, and workplace.

The lung is the most common site of injury by airborne pollutants. Acute effects, however, may also include non-respiratory signs and symptoms, which may depend upon toxicological characteristics of the substances and host-related factors.

Heavy industry-related occupational hazards are generally regulated and likely to be dealt with by an on-site or company physician or other health personnel². This booklet addresses the indoor air pollution problems that may be caused by contaminants encountered in the daily lives of persons in their homes and offices. These are the problems more likely to be encountered by the primary health care provider.

Etiology can be difficult to establish because many signs and symptoms are nonspecific, making differential diagnosis a distinct challenge. Indeed, multiple pollutants may be involved. The challenge is further compounded by the similar manifestations of many of the pollutants and by the similarity of those effects, in turn, to those that may be associated with allergies, influenza, and the common cold. Many effects may also be associated, independently or in combination with, stress, work pressures, and seasonal discomforts.

Because a few prominent aspects of indoor air pollution, notably environmental tobacco smoke and "sick building syndrome," have been brought to public attention, individuals may volunteer suggestions of a connection between respiratory or other symptoms and conditions in the home or, especially, the workplace. Such suggestions should be seriously considered and pursued, with the caution that such attention could also lead to inaccurate attribution of effects. Questions listed in the diagnostic leads sections will help determine the cause of the health problem. The probability of an etiological association increases if the individual can convincingly relate the disappearance or lessening of symptoms to being away from the home or workplace.

How To Use This Booklet

The health professional should use this booklet as a tool in diagnosing an individual's signs and symptoms that could be related to an indoor air pollution problem. The document is organized according to pollutant or pollutant group. Key signs and symptoms from exposure to the pollutant(s) are listed, with diagnostic leads to help determine the cause of the health problem. A quick reference summary of this information is included in this booklet. Remedial action is suggested, with comment providing more detailed information in each section. References for information included in each section are listed at the end of this document.

It must be noted that some of the signs and symptoms noted in the text may occur only in association with significant exposures, and that effects of lower exposures may be milder and more vague, unfortunately underscoring the diagnostic challenge. Further, signs and symptoms in infants and children may be atypical (some such departures have been specifically noted).

The reader is cautioned that this is not an all-inclusive reference, but a necessarily selective survey intended to suggest the scope of the problem. A detailed medical history is essential, and the diagnostic checklist may be helpful in this regard. Resolving the problem may sometimes require a multi-disciplinary approach, enlisting the advice and assistance of others outside the medical profession. The references cited throughout and the For Assistance and Additional Information section will provide the reader with additional information.

Diagnostic Quick Reference

1. Associated especially with formaldehyde.
2. In asthma.
3. Hypersensitivity pneumonitis, Legionnaires' Disease.
4. Particularly associated with high CO levels.
5. Hypersensitivity pneumonitis, humidifier fever.
6. With marked hypersensitivity reactions and Legionnaires' Disease.

Particular Effects Seen in Infants and Children

Environmental Tobacco Smoke: frequent upper respiratory infections, otitis media; persistent middle-ear effusion; asthma onset, increased severity; recurrent pneumonia, bronchitis.

Acute Lead Toxicity: irritability, abdominal pain, ataxia, seizures, loss of consciousness.

Diagnostic Checklist

It is vital that the individual and the health care professional comprise a cooperative diagnostic team in analyzing diurnal and other patterns that may provide clues to a complaint's link with indoor air pollution. A diary or log of symptoms correlated with time and place may prove helpful. If an association between symptoms and events or conditions in the home or workplace is not volunteered by the individual, answers to the following questions may be useful, together with the medical history.

The health care professional can investigate further by matching the individual's signs and symptoms to those pollutants with which they may be associated, as detailed in the discussions of various pollutant categories.

• When did the [symptom or complaint] begin?
• Does the [symptom or complaint] exist all the time, or does it come and go? That is, is it associated with times of day, days of the week, or seasons of the year?
• (If so) Are you usually in a particular place at those times?
• Does the problem abate or cease, either immediately or gradually, when you leave there? Does it recur when you return?
• What is your work? Have you recently changed employers or assignments, or has your employer recently changed location?
• (If not) Has the place where you work been redecorated or refurnished, or have you recently started working with new or different materials or equipment? (These may include pesticides, cleaning products, craft supplies, et al.)
• What is the smoking policy at your workplace? Are you exposed to environmental tobacco smoke at work, school, home, etc.?
• Describe your work area.
• Have you recently changed your place of residence?
• (If not) Have you made any recent changes in, or additions to, your home?
• Have you, or has anyone else in your family, recently started a new hobby or other activity?
• Have you recently acquired a new pet?
• Does anyone else in your home have a similar problem? How about anyone with whom you work? (An affirmative reply may suggest either a common source or a communicable condition.)

NOTE: A more detailed exposure history form, developed by the U.S. Public Health Service's Agency for Toxic Substances and Disease Registry (ATSDR) in conjunction with the National Institute for Occupational Safety and Health, is available from: Allen Jansen, ATSDR, 1600 Clifton Road, N.E., Mail Drop E33, Atlanta, Georgia 30333, (404) 639-6205. Request "Case Studies in Environmental Medicine #26: Taking an Exposure History." Continuing Medical Education Credit is available in conjunction with this monograph.

Health Problems Related To
ENVIRONMENTAL TOBACCO SMOKE

Key Signs/Symptoms in Adults ...

rhinitis/pharyngitis, nasal congestion, persistent cough conjunctival irritation headache wheezing (bronchial constriction) exacerbation of chronic respiratory conditions ... and in Infants and Children asthma onset increased severity of, or difficulty in controlling, asthma frequent upper respiratory infections and/or episodes of otitis media persistent middle-ear effusion snoring repeated pneumonia, bronchitis

Diagnostic Leads

• Is individual exposed to environmental tobacco smoke on a regular basis?
• Test urine of infants and small children for cotinine, a biomarker for nicotine

Remedial Action

While improved general ventilation of indoor spaces may decrease the odor of environmental tobacco smoke (ETS), health risks cannot be eliminated by generally accepted ventilation methods. Research has led to the conclusion that total removal of tobacco smoke - a complex mixture of gaseous and particulate components - through general ventilation is not feasible.³

The most effective solution is to eliminate all smoking from the individual's environment, either through smoking prohibitions or by restricting smoking to properly designed smoking rooms. These rooms should be separately ventilated to the outside.⁴

Some higher efficiency air cleaning systems, under select conditions, can remove some tobacco smoke particles. Most air cleaners, including the popular desk-top models, however, cannot remove the gaseous pollutants from this source. And while some air cleaners are designed to remove specific gaseous pollutants, none is expected to remove all of them and should not be relied upon to do so. (For further comment, see Questions That May Be Asked - Can Other Air Cleaners Help?)

Comment

Environmental tobacco smoke is a major source of indoor air contaminants. The ubiquitous nature of ETS in indoor environments indicates that some unintentional inhalation of ETS by nonsmokers is unavoidable. Environmental tobacco smoke is a dynamic, complex mixture of more than 4,000 chemicals found in both vapor and particle phases. Many of these chemicals are known toxic or carcinogenic agents. Nonsmoker exposure to ETS-related toxic and carcinogenic substances will occur in indoor spaces where there is smoking.

All the compounds found in "mainstream" smoke, the smoke inhaled by the active smoker, are also found in "sidestream" smoke, the emission from the burning end of the cigarette, cigar, or pipe. ETS consists of both sidestream smoke and exhaled mainstream smoke. Inhalation of ETS is often termed "secondhand smoking", "passive smoking", or "involuntary smoking."

The role of exposure to tobacco smoke via active smoking as a cause of lung and other cancers, emphysema and other chronic obstructive pulmonary diseases, and cardiovascular and other diseases in adults has been firmly established.^5,6,7 Smokers, however, are not the only ones affected.

The U.S. Environmental Protection Agency (EPA) has classified ETS as a known human (Group A) carcinogen and estimates that it is responsible for approximately 3,000 lung cancer deaths per year among nonsmokers in the United States.⁸ The U.S. Surgeon General, the National Research Council, and the National Institute for Occupational Safety and Health also concluded that passive smoking can cause lung cancer in otherwise healthy adults who never smoked.^9,10,11

Children's lungs are even more susceptible to harmful effects from ETS. In infants and young children up to three years, exposure to ETS causes an approximate doubling in the incidence of pneumonia, bronchitis, and bronchiolitis. There is also strong evidence of increased middle ear effusion, reduced lung function, and reduced lung growth. Several recent studies link ETS with increased incidence and prevalence of asthma and increased severity of asthmatic symptoms in children of mothers who smoke heavily. These respiratory illnesses in childhood may very well contribute to the small but significant lung function reductions associated with exposure to ETS in adults. The adverse health effects of ETS, especially in children, correlate with the amount of smoking in the home and are often more prevalent when both parents smoke.¹²

The connection of children's symptoms with ETS may not be immediately evident to the clinician and may become apparent only after careful questioning. Measurement of biochemical markers such as cotinine (a metabolic nicotine derivative) in body fluids (ordinarily urine) can provide evidence of a child's exposure to ETS.¹³

The impact of maternal smoking on fetal development has also been well documented. Maternal smoking is also associated with increased incidence of Sudden Infant Death Syndrome, although it has not been determined to what extent this increase is due to in utero versus postnatal (lactational and ETS) exposure.¹⁴

Airborne particulate matter contained in ETS has been associated with impaired breathing, lung diseases, aggravation of existing respiratory and cardiovascular disease, changes to the body's immune system, and lowered defenses against inhaled particles.¹⁵ For direct ETS exposure, measurable annoyance, irritation, and adverse health effects have been demonstrated in nonsmokers, children and spouses in particular, who spend significant time in the presence of smokers.^16,17 Acute cardiovascular effects of ETS include increased heart rate, blood pressure, blood carboxyhemoglobin; and related reduction in exercise capacity in those with stable angina and in healthy people. Studies have also found increased incidence of nonfatal heart disease among nonsmokers exposed to ETS, and it is thought likely that ETS increases the risk of peripheral vascular disease, as well.¹⁸

Health Problems Caused By
OTHER COMBUSTION PRODUCTS (Stoves, Space Heaters, Furnaces, Fireplaces)

Key Signs/Symptoms

• dizziness or headache
• confusion
• nausea/emesis
• fatigue
• tachycardia
• eye and upper respiratory tract irritation
• wheezing/bronchial constriction
• persistent cough
• elevated blood carboxyhemoglobin levels
• increased frequency of angina in persons with coronary heart disease

Diagnostic Leads

• What types of combustion equipment are present, including gas furnaces or water heaters, stoves, unvented gas or kerosene space heaters, clothes dryers, fireplaces? Are vented appliances properly vented to the outside?
• Are household members exhibiting influenza-like symptoms during the heating season? Are they complaining of nausea, watery eyes, coughing, headaches?
• Is a gas oven or range used as a home heating source?
• Is the individual aware of odor when a heat source is in use?
• Is heating equipment in disrepair or misused? When was it last professionally inspected?
• Does structure have an attached or underground garage where motor vehicles may idle?
• Is charcoal being burned indoors in a hibachi, grill, or fireplace?

Remedial Action

Periodic professional inspection and maintenance of installed equipment such as furnaces, water heaters, and clothes dryers are recommended. Such equipment should be vented directly to the outdoors. Fireplace and wood or coal stove flues should be regularly cleaned and inspected before each heating season. Kitchen exhaust fans should be exhausted to outside. Vented appliances should be used whenever possible. Charcoal should never be burned inside. Individuals potentially exposed to combustion sources should consider installing carbon monoxide detectors that meet the requirements of Underwriters Laboratory (UL) Standard 2034. No detector is 100% reliable, and some individuals may experience health problems at levels of carbon monoxide below the detection sensitivity of these devices.

Comment

Aside from environmental tobacco smoke, the major combustion pollutants that may be present at harmful levels in the home or workplace stem chiefly from malfunctioning heating devices, or inappropriate, inefficient use of such devices. Incidents are largely seasonal. Another source may be motor vehicle emissions due, for example, to proximity to a garage (or a loading dock located near air intake vents).

A variety of particulates, acting as additional irritants or, in some cases, carcinogens, may also be released in the course of combustion. Although faulty venting in office buildings and other nonresidential structures has resulted in combustion product problems, most cases involve the home or non-work-related consumer activity. Among possible sources of contaminants: gas ranges that are malfunctioning or used as heat sources; improperly flued or vented fireplaces, furnaces, wood or coal stoves, gas water heaters and gas clothes dryers; and unvented or otherwise improperly used kerosene or gas space heaters.

The gaseous pollutants from combustion sources include some identified as prominent atmospheric pollutants -- carbon monoxide (CO), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂).

Carbon monoxide is an asphyxiant. An accumulation of this odorless, colorless gas may result in a varied constellation of symptoms deriving from the compound's affinity for and combination with hemoglobin, forming carboxyhemoglobin (COHb) and disrupting oxygen transport. The elderly, the fetus, and persons with cardiovascular and pulmonary diseases are particularly sensitive to elevated CO levels. Methylene chloride, found in some common household products, such as paint strippers, can be metabolized to form carbon monoxide which combines with hemoglobin to form COHb. The following chart shows the relationship between CO concentrations and COHb levels in blood.

Tissues with the highest oxygen needs -- myocardium, brain, and exercising muscle -- are the first affected. Symptoms may mimic influenza and include fatigue, headache, dizziness, nausea and vomiting, cognitive impairment, and tachycardia. Retinal hemorrhage on funduscopic examination is an important diagnostic sign¹⁹, but COHb must be present before this finding can be made, and the diagnosis is not exclusive. Studies involving controlled exposure have also shown that CO exposure shortens time to the onset of angina in exercising individuals with ischemic heart disease and decreases exercise tolerance in those with chronic obstructive pulmonary disease (COPD)²⁰.

Note: Since CO poisoning can mimic influenza, the health care provider should be suspicious when an entire family exhibits such symptoms at the start of the heating season and symptoms persist with medical treatment and time.