Indoor Air Quality & Human Health

Isaac Turiel

• Publisher: Routledge
• Year: 2012
• Print ISBN: 9780419138709
• eBook ISBN: 9781135259228
• Topic: Architecture
• Subtopic: Architecture Methods & Materials

First published in 1985. This book seeks to fill the gap of publicly available and understandable information on the subject of indoor air pollution and its public health effects. Its purpose is to provide general information on indoor air pollution sources and the pollutants commonly found indoors, and also to explore the potential health effects arising from exposure to these pollutants

1

Introduction

On the average, North Americans and Europeans spend 80 to 90 percent of their time indoors; thus, the air we breathe is mostly indoor air. Although that may appear to be obvious, until recent years most health studies did not take this fact into account. In the past, studies concerned with the effects of air pollutants on human health considered only the exposure to outdoor pollutants, but indoor pollutants are a distinct and diverse group of their own.

In order to understand the effects of airborne substances on human health, it is important to know how much time people spend both outdoors and indoors, and also the concentrations of the pollutants to which they are exposed. Working people divide their time between home and work, while homemakers spend as much as 85 percent of their time at home. At home, people smoke, cook, paint, clean, heat the air for comfort, and carry out many other activities that can add harmful substances to the indoor air. The house itself, even the soil beneath it, can be a source of indoor air contaminants. Table 1.1 summarizes the main sources of indoor air pollutants and the contaminants they emit. Note that not all of these contaminants come from indoor sources.

Awareness of indoor air quality could be said to be a child of the 1973 oil embargo, for with that event came the surge of energy-conserving practices and devices that had a direct effect on the nation's indoor air. Making machines run more efficiently and designing furnaces to waste less heat are entirely beneficial actions, but putting certain types of insulation in houses, reducing ventilation in office buildings, and stopping drafts by “tightening” homes had unexpected side effects: indoor air pollution– related complaints began to increase as pollutants were kept bottled up indoors for longer periods of time. It should be noted that not all indoor air quality problems are a result of energy-efficiency improvements.

Table 1.1. Summary of Sources and Types of Indoor Air Pollutants

Sources	Pollutant types
Outdoor
Stationary sources	Sulfur dioxide, ozone, particulates, carbon monoxide, hydrocarbons
Motor vehicles	Carbon monoxide, lead, nitrogen oxides
Soil	Radon, microorganisms
Indoor
Building construction materials
Concrete, stone	Radon
Particle board, plywood	Formaldehyde
Insulation	Formaldehyde, fiberglass
Fire retardant	Asbestos
Paint	Organics, lead
Building contents
Heating and cooking combustion appliances	Carbon monoxide, nitrogen oxides, formaldehyde, particulates
Copy machines	Ozone, organics
Water service	Radon
Human occupants
Metabolic activity	Carbon dioxide, water vapor, odorants
Biological activity	Microorganisms
Human activities
Tobacco smoking	Carbon monoxide, particulates, odorants
Aerosol sprays	Fluorocarbons, odorants
Cleaning	Organics, odorants
Hobbies and crafts	Organics, odorants

Several of these pollutants are of great importance and appear frequently in the news. Although our knowledge is still incomplete, the consensus is that three contaminants deserve the most intense study: (1) radon, a natural radioactive gas, (2) formaldehyde, a widely used chemical that emanates from many household items, and (3) tobacco smoke. The health effects involved range from eye and throat irritation through asthma and chronic respiratory disease to lung cancer.

These three do not exhaust the list. Residential kerosene heaters have dangers known and not-so-well known. Schools and offices may subject their occupants to asbestos-laden air. Many modern, airtight offices have been subject to epidemics of “tight-building syndrome.” Utility-sponsored programs to weatherize houses, if not done carefully, may have unexpected impacts on customers’ health. Finally, there are the spectacular outbreaks of illnesses such as Legionnaire's disease. This book provides the most up-to-date information for each of these issues, including ways to control exposure to contaminants indoors.

Exposures and Standards

Two factors that must be assessed in order to predict health effects are exposure levels and typical human responses for various levels of exposure. The type of exposure meant here is an integrated exposure, that is, the mathematical product of a pollutant concentration a person is exposed to and the time period over which the exposure occurs. Because the concentrations of pollutants that an individual is exposed to over the course of a day are often highly variable, the job of determining integrated exposures can be very difficult. Exposures may be acute (high concentrations for short time periods) or chronic (low concentrations for long time periods). Adverse health effects can be produced by either type of exposure.

For some airborne pollutants, the health effects of short-term exposures are well known. Data are often lacking, however, for long-term exposures to low concentrations of pollutants as experienced by occupants of residential and commercial buildings. The effect of a pollutant is often expressed in the form of a dose-response relationship. The response may range from eye irritation or headaches to lung cancer or death. For most of the pollutants we consider, the dose can be thought of as the amount of contaminant inhaled and reaching a particular part of the body; the dose is thus dependent upon the integrated exposure, the rate at which the individual takes in air, and the body's clearance rate for each contaminant. It is important to keep in mind that individuals vary in their respiratory rates and in their responses to various contaminants.

The federal government's efforts to monitor and improve air quality have concentrated on measuring pollutant concentrations in outdoor air and on controlling sources of outdoor air pollution. Because of this emphasis, there are large gaps in our knowledge of the integrated exposures to air pollutants experienced by various segments of the population. For example, we know comparatively little about the characteristics and concentrations of pollutants that homemakers, young children, and infirm adults are exposed to at home; neither are office workers a well-studied group. There are, however, a substantial number of studies from which we can make inferences about the range of exposures experienced by these groups given specific assumptions.

Once typical exposures are determined, health effects can be estimated for some pollutants. In this book we compare typical pollutant exposures to either dose-response relationships or to government health standards. These two approaches are often equivalent, since in most cases the health standards are derived from analysis of dose-response relationships. The health standards we refer to are those established by the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA). Although these health standards were not promulgated to apply to residential or office environments, they may be so used where the criteria they were based on are reasonable for that environment.

Table 1.2. National Primary Air Quality Standards

		Long-term		Short-term
Contaminant		Concentration (ppm)	Averaging time (years)	Concentration (ppm)	Averaging time (hours)
	Sulfur oxides	0.03	1	0.14	24
	Carbon monoxide	__	__	9.0	8
		__	__	35.0	1
	Ozone	__	__	0.12	1
	Nitrogen dioxide	0.05	1	__	__
	Particulates	75.0^a	1	260.0	24

^aMeasured in micrograms per cubic meter (µg/m³).

The Clean Air Act of 1970 directed the EPA to establish national standards for ambient air quality, which has thus far been interpreted to mean outdoor air. In 1971 the EPA announced final publication of national air quality standards for several classes of pollutants, including particulate matter, carbon monoxide, photochemical oxidants (mainly ozone), and nitrogen oxides. Although EPA standards apply to outdoor air, they were promulgated to protect the health of individuals of all ages, healthy or infirm. Therefore, assuming that the standards were soundly arrived at, for our purpose they can often be applied, with care, to indoor situations.* In particular, we will refer to the standards for ozone, carbon monoxide, and nitrogen oxides when attempting to predict the health effects resulting from indoor exposures to these pollutants. Indoor particulates, however, may be quite different from outdoor particulates: for example, tobacco-smoke particulates, often found indoors, are generally more harmful than the particulates found in outdoor air (such as ash, pollen, and soil).

Table 1.2 lists the EPA air quality standards. For some contaminants, such as carbon monoxide, there are two standards. A higher concentration is permissible for a shorter time period. The average carbon monoxide concentration for an 8-hour averaging period may not exceed 9 ppm (parts per million); for a 1-hour time period, however, the permissible concentration may go as high as 35 ppm.

A concentration of 35 ppm of carbon monoxide in air means that 35 of every million molecules in a sample of air are carbon monoxide molecules. Concentrations of gases can also be expressed in micrograms per cubic meter, a mass density. Particulate concentrations are always given as a mass density; that is, as a quantity of mass (often expressed in grams) that is found in some volume of air (for example, a cubic meter).

The occupational standards established by OSHA are designed to protect the health of most workers who are exposed to hazardous chemicals only during a 40-hour work week. They were intended to be applied to industrial environments. Office workers fall in a gray area, since they belong to the category of workers, but their activities are not carried out in an industrial environment. The National Institute of Occupational Safety and Health (NIOSH), a research arm of OSHA, and some state public health departments have been investigating indoor air problems in office buildings and, for lack of more applicable standards, have been applying OSHA standards. In this book, the most appropriate health standard will be chosen for determining health effects of a pollutant.

Air Infiltration

Substances emitted into the indoor air have much less opportunity to become diluted than those emitted outdoors, where there is a large vo...

Table of contents

• Front cover
• Title Page
• Copyright
• Preface
• Contents
• 1 Introduction
• 2 Formaldehyde and Other Household Contaminants
• 3 Radon
• 4 Particulates
• 5 Combustion Products
• 6 Involuntary Smoking
• 7 Energy-Efficient Buildings and Indoor Air Quality
• 8 Control of Indoor Air Pollutants
• 9 Indoor Air Quality Problems in Office Buildings
• 10 Legal and Regulatory Issues
• Appendixes
• Sources and Suggested Reading
• Glossary
• Index