Volatile Organic Chemicals (VOCs) are carbon-containing compounds emitted as gases from certain solids or liquids. They evaporate easily from water into air at normal air temperatures. This high vapor pressure (and low boiling point) at room temperature is why you can easily detect the distinctive odor of gasoline and many solvents, as the VOCs exit into the air. Large numbers of molecules evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. Another example is formaldehyde slowly exiting paint and getting into the air.
What are the different types of VOCs?
VOCs are many and varied in number. VOCs include both human-made and naturally occurring chemical compounds. For an example in nature, VOCs play an important role in communication between plants. VOCs are contained in thousands of industrial, commercial and residential products. They are found in fuel oils and solvents, cleaners and degreasers, paints and lacquers, inks and dyes, cosmetics, refrigerants and pesticides. Hobby and craft materials contain VOCs, including glues and adhesives, permanent markers and photographic solutions. Office equipment contains VOCs in copiers and printers, correction fluid and copy paper. All of these products can release organic compounds while you are using them, and, to some degree, when they are stored. People are most commonly exposed to VOCs through the air, through skin contact, in food, and potentially in drinking water supplies.
There are two main categories of VOCs: chlorinated solvents and fuel components. Chlorinated solvents are widely used in industry settings and in common household products. These chemicals are or have been used as degreasing fluids for many different purposes such as dry cleaning clothes, decaffeinating coffee, and dissolving grease build-up in septic tanks. Some chlorinated solvents are found in spot removers, automotive cleaners, and wood furniture polishes. Vinyl chloride is used to make plastic materials, such plastic wrap and water pipes. Fuel components are chemicals that are found in products such as gasoline, kerosene and heating oil. For example, methyl tert-butyl ether (MTBE) is added to gasoline as an octane-booster and “oxygenator” to reduce carbon monoxide emissions. Benzene, toluene and xylene have been used as solvents in the workplace and as components in glues, paints and cleaners in the household. Benzene is also found in car exhaust and cigarette smoke.
How do VOCs get into my drinking water?
Most VOCs found in the environment result from human activity. VOCs can move easily through the environment. If improperly discarded onto the ground, a portion will evaporate but some can soak through the soil and eventually end up in the groundwater. Benzene, for example, can enter ground water from fuel spills on the surface or from leaking gas tanks underground. Other examples of VOCs commonly detected in groundwater are methylene chloride, an industrial solvent and perchloroethylene, a dry-cleaning chemical. Once in the soil, VOCs may be carried deeper by rain or melting snow, to eventually reach the groundwater table. When VOCs migrate underground to nearby wells, they can eventually end up in drinking water supplies. VOCs are not usually found in drinking water that comes from a surface water source, such as a river or lake, because they tend to evaporate from the water into the air.
Public water systems are required to be monitored on a routine basis for contamination. For private water supplies, however, it is the homeowner’s responsibility to regularly have their water quality evaluated.
In our next blog, we will look further at volatile organic compounds. We will consider specifically what happens once they enter our homes. What effects can VOCs have on our health? And what can we do to reduce VOCs from our drinking water?