Glossary

Units
kg kilogram
mcg or µg microgram
mEq milliequivalent
mg milligram
mg/dL milligrams per deciliter
mmHg millimeters of mercury, 1 mmHg = 1 torr
ng/mL nanograms per milliliter
nM/L or nmol/L nanomoles per liter
nm nanometer, one billionth of a meter
Upper Limit (UL)
Maximum daily nutrient intake amount that is unlikely to pose risks of adverse health effects.
Ultraviolet Radiation (UV or UVR)
Light that is produced by the sun or sunlamps. Ultraviolet light is the portion of the electromagnetic spectrum with wavelengths shorter than visible light and is split into 3 bands:
Ultraviolet A (UVA): wavelength 315–400 nm. UVA penetrates deep into the skin and can cause damage like wrinkles and discolouration. UVA's intensity is more constant than UVB, as it does not vary with time of day or year. No UVA is blocked by the ozone layer nor is it filtered by glass. Sunscreen lotions do not protect against UVA unless they are wide-spectrum.
Ultraviolet B (UVB): wavelength 280–315 nm. UVB can cause sunburn yet is also what enables vitamin D production in the skin by 7–dehydrocholesterol. Dependent upon the angle at which the sun's rays reach the earth, optimal UVB exposure is between 10:00 am–2:00 pm and in the summer (70% of a person's yearly dose is received in summer). Sunscreens block UVB, preventing vitamin D production. UVB does not penetrate glass and most is blocked by the ozone layer.
Ultraviolet C (UVC): wavelength less than 280 nm. All UVC is blocked by the ozone layer.