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

A naturally-occurring poisonous metal element which occurs naturally in the earth's surface.

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

A chemical that is required for metabolic processes, which must be taken from food or another external source. Macronutrients taken from food sources include carbohydrates, proteins, fats and vitamins.

A lipid, any of a diverse group of organic compounds including fats, oils, hormones and certain components of membranes that are grouped together because they do not interact appreciably with water, combined chemically with oxygen.

Vegetable oils that have been hydrogenated or partially hydrogenated for the purpose of being solid at room-temperature, which contain trans-fats.

A family of fluorine-containing chemicals with unique properties to make materials stain- and stick-resistant.

A former commercially produced synthetic organic chemical compound that may be present in products and materials produced before the 1979 PCB ban.

A synthetic resin used chiefly in paints and varnishes. Diisocyanates in polyurethane products can be toxic if inhaled or touched during installation.

Radioactive, carcinogenic noble gas generated from the decay of natural deposits of uranium.

Neurotransmitter hormone produced in the gut and brain stem which regulates mood, sleep and digestion.

Sodium is consumed as sodium chloride in common salt. It is a vital nutrient, but unhealthy in high amounts.

A chlorinated hydrocarbon used as a dry cleaning solvent, an additive in textile processing and metal degreasing that has been linked to cancer.

A poisonous substance produced by a living organism.

Also called nanoparticles, ultrafine particles are a subcategory of PM₂.₅ which are exclusively less than 0.1 µm. Due to the small size they are often airborne and can easily reach the alveoli of the lungs.

Organic, and therefore carbon and hydrogen containing, materials which evaporate and diffuse easily at ambient temperature. VOCs are emitted by a wide array of building materials, paints and common consumer products.

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.

Measurement of luminous intensity and the SI base unit of light.

Comparison of the appearance of 8 to 14 colors under a light source in question, to a blackbody source of the same color temperature. CRI or Ra refers to the average of the first 8 comparisons and R9 describes the lighting accuracy on red surfaces.

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

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.

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

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.

Extent to which a physical structure blocks out sound, typically used in describing flooring, a higher IIC reduces footfall noise, and other impact sounds.

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.

Unit of illuminance, one lux being equivalent to one lumen per square meter.

Enforceable water quality limits for a substance, based on the Maximum Contaminant Level Goal, but taking into account technology and cost limitations of treatment.

Rate that chemical energy in the body is converted to heat and mechanical energy.

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

Measure the turbidity of water.

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.

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

A non-SI unit of radioactivity.

Time it takes for sound to decay. The most commonly used reverberation time is RT60, the time it takes for the sound level to decrease 60 decibels. Additional reverberation time measurements are RT20 and RT30, for decreases of 20 and 30 decibels, respectively.

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.

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

The distance between two points on a wave in which the wave repeats itself. Often used to describe light waves.