Stressors: Physical

Introduction

This entry describes the measurement of physical environmental stressors and design elements that affect human well-being. We discuss stressors encountered in both outdoor and indoor environments, including residential and work settings.

First, we will describe the three most commonly recognized environmental stressors—noise, crowding and air quality (see Table 1) (Evans, 1999). Second, we will discuss measures of overall housing or building quality. Finally, we will describe specific design characteristics that may have an impact on health or well-being. These features include floor height, architectural depth, and characteristics of floor plan (e.g. enclosure and proximity).

Noise

Exposure to noise has been empirically linked to both auditory and non-auditory effects. Non-auditory effects of noise include physiological detriments (increased heart rate or blood pressure), low motivation, and poor cognitive or attentional performance (Evans & Lepore, 1993; Evans, 2001). Auditory effects of exposure to loud sound include short term acuity loss (‘temporary threshold shift’) and, over time, permanent hearing loss (‘permanent threshold shift’) (Kryter, 1994). Noise is defined as unwanted sound. In other words, while sound is a physical phenomenon, noise is a psychological phenomenon—bothersome or annoying sound. Typically, noise is measured using the logarithmic decibel (dBA) scale. An increase in [Page 926]10 dBA is perceived as approximately twice as loud. Exposure to noise is measured over a period of time, often 24 hours. Because noise at nighttime is generally more annoying to people, another strategy is to weigh nighttime noise exposure more heavily than daytime noise (Ldn).

Crowding

The distinction between density and crowding parallels that between sound and noise. Density is a physical index, whereas crowding depends on an individuaL's cognitive appraisal of need for space (Stokols, 1972). Often, however, density is interpreted as a measure of crowding. There are two types of density—interior density and exterior density. Exterior density refers to the number of people in a geographic area, such as a square mile, an acre or an urban block. Interior density, in contrast, is typically measured by the number of residents per room in a household. There is considerable evidence that interior density is a more meaningful measure with respect to human health than is exterior density (Baum & Paulus, 1987). Customarily, people-to-room ratios exceeding 1.0 are considered ‘crowded’, but it is also common to question occupants regarding their perceptions of crowding.

Air Quality

Together outdoor air pollution and indoor air quality constitute another type of environmental stressor: air quality. Indoor air quality issues include volatile organic compounds (VOCs), radon, carbon monoxide, and suspended particulates. A source for air quality information is the Environmental Protection Agency's (EPA) website (http://www.epa.gov/ebtpages/aindoorairpollution.html).