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Lead (Pb): A soft, heavy, blue-gray metal. It occurs naturally in the earth’s crust, and human activities such as burning fossil fuels, mining, and manufacturing have spread it throughout the environment, including our homes and workplaces. Lead is hazardous to human health. Lead can occur in the air as small particles, often from emissions from lead smelters and other metal-processing plants. Lead exposure can also occur through:

  • Eating food or drinking water that contains lead,
  • Eating lead-based paint chips, chewing on objects painted with lead-based paint, or swallowing house dust or soil that contains lead are the most common routes of exposure to lead for small children,
  • Engaging in certain hobbies in which lead is used (for example, making stained glass),
  • Swallowing or breathing chips or dust from lead-based paints,
  • Using health-care products or folk remedies that contain lead,
  • Working in a job where lead is used.

Low birth weight: A baby is considered to be of low birth weight when its weight is less than 5.5 lbs., or 2500 grams, at birth. For Tracking, low birth weight is measured among singleton births only.

Lower limb reduction defects: Lower limb reduction defects occur when a part of or the entire leg (lower limb) of a fetus fails to form completely during pregnancy. The defect is referred to as a "limb reduction" because a limb is reduced from its normal size or is missing.

Lung disease: A broad term that refers to many disorders affecting the lungs. Lung disease includes diseases such as asthma, emphysema, and chronic bronchitis.


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Mean: The average of a list of numbers by calculating the sum of all the members of the list and dividing by the number of items in the list.

Measure: On the Tracking Network, a measure is a summary characteristic or statistic, such as a sum, percentage, or rate. Measures are available for each indicator.

Mercury: A naturally occurring element that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Elemental or metallic mercury is a shiny, silver-white metal and is liquid at room temperature. It is used in thermometers, fluorescent light bulbs and some electrical switches. When dropped, elemental mercury breaks into smaller droplets which can go through small cracks or become strongly attached to certain materials. At room temperature, exposed elemental mercury can evaporate to become an invisible, odorless toxic vapor. People can be exposed to elemental mercury vapor when products that contain mercury break and expose mercury to the air, particularly in poorly-ventilated spaces. Inorganic mercury compounds take the form of mercury salts and are generally white powder or crystals, with the exception of mercuric sulfide (cinnabar) which is red.

Inorganic mercury compounds have been included in products such as fungicides, antiseptics or disinfectants. Some skin lightening and freckle creams, as well as some traditional medicines, can contain mercury compounds.

Organic mercury compounds, such as methyl mercury, are formed when mercury combines with carbon. Microscopic organisms convert inorganic mercury into methyl mercury, which is the most common organic mercury compound found in the environment. Methyl mercury accumulates up the food chain.

Metadata: This is simply "data about data". Metadata is the information about a data source, for example, a book contains information, but there is also information about that book such as the author and publisher - this is the metadata.

Metal: A chemical element that usually has a shiny surface, is generally a good conductor of heat and electricity, and can be melted or fused, hammered into thin sheets, or drawn into wires. The metals comprise about two-thirds of all known elements. Unlike nonmetals, metals form positive ions and basic oxides and hydroxides. Upon exposure to moist air, many metals react chemically with the oxygen of the atmosphere to form a metallic oxide, such as rust on exposed iron.

Microgram: A unit of mass equal to one millionth of a gram.

Micron: A unit of length equal to one millionth of a meter.

Microorganisms: Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when consumed in drinking water. Also known as microbes.

Milligram: A unit of mass equal to one thousandth of a gram.

Morbidity: State of being ill or diseased. Morbidity is the occurrence of a disease or condition that alters health and quality of life.

Mortality: Death.

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New Hampshire Environmental Public
Health Tracking Program
NH Department of Health and Human Services,
Division of Public Health Services
29 Hazen Drive  |  Concord, NH 03301
(603) 271-4988  |  (800) 852-3345 ext.4988