Science Terms Definitions - S

Sanitary Solid Waste - Non-radioactive and non-hazardous material including garbage, refuse, and other discarded solid sanitary waste materials including those materials resulting from industrial, commercial, and agricultural operations, and from community activities. Solid sanitary waste does not include solids or dissolved material in domestic sewage or other significant pollutants in water resources, such as silt, dissolved or suspended solids in industrial waste water effluents, dissolved materials in irrigation return flows or other common water pollutants.

Sanitary Waste - This waste stream consists of cardboard, paper, plastic, glass, metal, food waste, office waste, etc.

SARA - The Superfund Amendments and Reauthorization Act of 1986 was enacted to revise and extend the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980. CERCLA authorizes Federal cleanup of uncontrolled hazardous waste sites and the response to releases of hazardous substances. SARA and CERCLA fund the program to carry out the EPA solid waste emergency and long-term removal/remediation activities.

Secondary Drinking Water Regulations - Non-enforceable regulations applying to public water systems and specifying the maximum contamination levels that, in the judgment of EPA, are required to protect the public welfare. These regulations apply to any contaminants that may adversely affect the odor or appearance of such water and consequently may cause people served by the system to discontinue its use.

Secure Maximum Contaminant Level - Maximum permissible level of a contaminant in water delivered to the free flowing outlet of the ultimate user, or of contamination resulting from corrosion of piping and plumbing caused by water quality.

Sediment - Eroded soil and rock material, and plant debris, transported and deposited by water.

Sievert - A unit of equivalent absorbed dose equal to 100 rems.

Site - An area or place (usually contaminated) within the jurisdiction of the EPA and/or a state.

Site Assessment Program - A means of evaluating hazardous waste sites through preliminary assessments and site inspections to develop a Hazard Ranking System score.

Site Inspection - The collection of information from a Superfund site to determine the extent and severity of hazards posed by the site. It follows and is more extensive than a preliminary assessment. The purpose is to gather information necessary to score the site, using the Hazard Ranking System, and to determine if it presents an immediate threat requiring prompt removal.

Slope Factor - Toxicity value for evaluating the probability of an individual developing cancer from exposure to contaminant levels over a lifetime. See our toxicity values.

Solid Waste - Any solid, semi-solid, liquid and containerized gaseous material generated as a result of routine operations and/or construction/demolition activities. This is the legal definition per the Resource Conservation and Recovery Act.

Somatic Effects of Radiation - Effects of radiation limited to the exposed individual, as distinguished from genetic effects, which may also affect subsequent unexposed generations.

Source - A place where pollutants are emitted, for example a chimney stack.

Source Term - The release rate of hazardous agent from a facility or activity.

Special Nuclear Material (SNM) - SNM is defined in 10 CFR 20.1003 as "(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in isotope 235, and any other material that the NRC, pursuant to the provisions of section 51 of the Atomic Energy Act, determines to be SNM, but does not include source material; (2) or any material artificially enriched by any of the foregoing but does not include source material." SNM is important in the fabrication of weapons grade materials and as such has strict licensing and handling controls.

Specific Activity - A measure of the radioactivity of a unit weight (generally one gram) of material.

Spent Fuel - Spent fuel consists of irradiated fuel discharged from a nuclear reactor. Three categories of spent fuel are: fuel from commercial light-water reactors (LWRs), fuel from non-LWR commercial reactors, and special fuels associated with government-sponsored research and demonstration programs, universities, and private industries.

Spontaneous Fission - The spontaneous splitting of the nucleus into two new nuclei, generally with the emission of one or more neutrons and the release of energy.

Standard Deviation - A measure of dispersion or variation, usually taken as the square root of the variance.

Standard Geometric Deviation - Measure of dispersion of values about a geometric mean; the portion of the frequency distribution that is one standard geometric deviation to either side of the geometric mean; accounts for 68% of the total samples.

Standard Normal Deviation - Measure of dispersion of values about a mean value; the positive square root of the average of the squares of the individual deviations from the mean.

Statistical Significance - The statistical significance determined by using appropriate standard techniques of statistical analysis with results interpreted at the stated confidence level and based on data relating species which are present in sufficient numbers at control areas to permit a valid statistical comparison with the areas being tested.

Steady State Exposure - Exposure to an environmental pollutant whose concentration remains constant for a period of time.

Stochastic Effects - Effects that occur by chance, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose. In the context of radiation protection, the main stochastic effects are cancer and genetic effects.

Subchronic - Of intermediate duration, usually used to describe studies or levels of exposure between 5 and 90 days.

Superfund - The program operated under the legislative authority of CERCLA and SARA that funds and carries out EPA solid waste emergency and long-term removal and remedial activities. These activities include establishing the National Priorities List, investigating sites for inclusion on the list, determining their priority, and conducting and/or supervising the cleanup and other remedial actions.

Superfund Innovative Technology Evaluation - EPA program to promote development and use of innovative treatment technologies in Superfund site cleanups.

Surface Impoundment - Treatment, storage, or disposal of liquid hazardous wastes in ponds.

Surface Runoff - Precipitation, snow melt, or irrigation in excess of what can infiltrate the soil surface and be stored in small surface depressions; a major transporter of nonpoint source pollutants.

Surface Water - All water naturally open to the atmosphere (rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc.) and all springs, wells, or other collectors directly influenced by surface water.

Synergetic - Working together; an agent that works synergistically with one or more other agents.

Synergism - An interaction between two substances that results in a greater effect than either of the substances could have had acting independently.

Synergistic Effects - Joint effects of two or more agents, such as drugs that increase each other's effectiveness when taken together.

Systemic Effects - Systemic effects are those that require absorption and distribution of the toxicant to a site distant from its entry point, at which point effects are produced. Most chemicals that produce systemic toxicity do not cause a similar degree of toxicity in all organs, but usually demonstrate major toxicity to one or two organs. These are referred to as the target organs of toxicity for that chemical. Systemic effects do not include cancer.