Glossary

An element found in the earth’s crust that has applications in various industrial processes, however runoff from factories, agricultural practices and natural deposits can lead to high concentrations in water.

Enters groundwater and surface water by dissolution of rocks and soils, from atmospheric fallout and biological decays and waste disposal.

Widely used as a precursor to various materials such as detergents, dyes, pesticides, Styrofoam, nylon and other synthetic fibers.

Typical applications include solvents for the printing, rubber and leather industries as well as ingredients in paper and fabric coatings.

Among the most widely used pesticides in the United States and among the most commonly detected pesticide in drinking water.

A non-selective herbicide used in many pesticide formulations; exposure may result from its normal use due to spray drift, residues in food crops and from runoff into drinking water sources.

A highly irritating, greenish-yellow gaseous halogen, capable of combining with nearly all other elements, produced principally by electrolysis of sodium chloride and used widely to purify water, as a disinfectant and bleaching agent.

Chlorine in water can combine with organic matter to form compounds called disinfectant byproducts (DBPs), such as trihalomethanes.

Small amounts are required for a healthy diet, but higher amounts may cause neurological damage.

Sulfates occur naturally and can erode into water supplies; the health effects of sulfates are uncertain, but ingesting large amounts has been linked to negative health effects.

Bacteria and microscopic algae and fungi, especially those living in a particular site or habitat.

A potentially toxic and potentially cancer-causing substance that can be naturally present in uncooked, raw foods in very small amounts.

A measure of how many times the volume of air within a defined space is replaced, used in the context of building ventilation and air tightness.

Clothing insulation is the resistance to heat transfer provided by clothing measured in clo (1 clo = 0.155 m²K/W = 0.88°F ft²h/BTU).

Spectral distribution of electromagnetic radiation of a blackbody at a given temperature. For example, the color temperature during the daytime is approximately 15,000 K, while during sunset is approximately 1,850 K.

Temperature of air measured by a thermometer freely exposed to the air but shielded from radiation and moisture. This temperature is usually thought of as air temperature and it is the true thermodynamic temperature. Dry bulb temperature does not take humidity into account.

The number of times an event repeats itself per a specified unit of time. Hertz (Hz) is a common unit for frequency and equals cycles per second i.e. 1 Hz = 1 cycle/second. Most commonly used with waves (sound and light) and is the number of times the wave repeats itself at its particular wavelength.

Amount of light passing through a given area in space. Measured in lux or foot-candles.

Measure of luminous flux, derived from the SI base unit candela, and therefore weighted to the eye's sensitivity to light; 1 W of light at 555 nm equates to 683 lumens.

Total luminous output of a light source, measured in lumens. Weighted to the eye's visual sensitivity.

Concentration of a substance in drinking water believed to result in no adverse effects. Derived from on Population Adjusted Dose and estimated daily water consumption, fraction of exposure from water and body weight.

The uniform surface temperature of an imaginary black enclosure in which an occupant would gain or lose the same amount of radiant heat as in the actual non-uniform space; MRT is a primary driver of human thermal comfort, roughly equal in influence to air temperature.

Field test for determining the sound transmitting abilities of a wall. Higher NIC values indicate better sound insulation i.e. more effective sound cancellation between spaces. NIC specifications are defined in ASTM Standard E366.

A laboratory method for determining the sound transmission through a wall. Higher STC values indicate more effective noise isolation than lower ones. STC specifications are found in ASTM Standards E90-09 and E1425.

Define the sound pressure limits of the octave band spectra ranging from 63-8000 Hz. The noise criteria equals the lowest curve which is not exceeded in the spectrum.

Unit of illuminance, equivalent to one lumen per square foot.

Percentage of space in which the light level from direct sun alone exceeds a pre-defined threshold (such as 1000 lux) for some quantity of hours (such as 250) in a year.

A measure of light used to quantify how much a light source will stimulate melanopsin’s light response.

Measurement of the mass of a chemical or contaminate per unit volume of water.

A unit of measurement to express very dilute concentrations of substances.

Measures the mass of gas that passes through a certain point.

Unit of measurement for electromagnetic radiation, equal to 1/1000 watt. Not weighted to biological responses such as vision.

Amount of light in the visible portion of the spectrum that passes through a glazing material.

Average value that determines the absorptive properties of materials.