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| Sample | One or more items taken from a population (biota or non-biota) or a process and intended to provide information on the population or process. |
| Sampling | Procedure used to obtain or constitute a sample. |
| Scientific method | The principles and processes regarded as necessary for scientific investigation, including rules for concept or hypothesis formulation, conduct of experiments, and validation of hypotheses by analysis of observations. |
| Screening | Carrying out of a test or tests, examination(s) or procedure(s) in order to expose undetected abnormalities, unrecognized (incipient) diseases, or defects: examples Pharmacological or toxicological screening consists of a specified set of procedures to which a series of compounds is subjected to characterize pharmacological and toxicological properties and to establish dose-effect and dose-response relationships. |
| Screening Risk Assessment | A risk assessment performed with few data and many assumptions to identify exposures that should be evaluated more carefully for potential risk. |
| Sediment | Topsoil, sand, and minerals washed from the land into water, usually after rain or snow melt. |
| Sediments | Soil, sand, and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish and wildlife habitat, and clouding the water so that sunlight cannot reach aquatic plants. Careless farming, mining, and building activities will expose sediment materials, allowing them to wash off the land after rainfall. |
| Seepage | Percolation of water through the soil from unlined canals, ditches, laterals, watercourses, or water storage facilities. |
| Sensitivity analysis | A “what-if†type of analysis to determine the sensitivity of the outcomes to changes in parameters. If a small change in a parameter results in relatively large changes in the outcomes, the outcomes are said to be sensitive to that parameter. |
| SF (Slope Factor for carcinogenic potency) | Factor multiplied to the calculated dose to estimate the incremental lifetime cancer risk. Usually separate SF factors are provided for oral and inhalation. A Canadian term, similar to the US EPA Cancer Slope Factor (CSF). |
| Short-Term Outcomes (of risk management) | The impacts on those groups who are immediately affected by risk management strategies, including changes in service levels and behavior. |
| Silt | Sedimentary materials composed of fine or intermediate-sized mineral particles. |
| Sink | Place in the environment where a compound or material collects. |
| Site | An area or place 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. |
| Site Safety Plan | A crucial element in all removal actions, it includes information on equipment being used, precautions to be taken, and steps to take in the event of an on-site emergency. |
| Soil | The unconsolidated mineral and organic matter on the surface of the earth that has been subjected to and influenced by geologic and other environmental factors. |
| Soil Texture | A measure of the percentages of various particles size groups in a volume of soil, typically sand, silt and clay. |
| Solubility | The amount of mass of a compound that will dissolve in a unit volume of solution. Aqueous Solubility is the maximum concentration of a chemical that will dissolve in pure water at a reference temperature. |
| Sorption | The action of soaking up or attracting substances; process used in many pollution control systems. |
| Species | 1. A reproductively isolated aggregate of interbreeding organisms having common attributes and usually designated by a common name.2. An organism belonging to belonging to such a category. |
| Spring | Ground water seeping out of the earth where the water table intersects the ground surface. |
| SSRA | Site-specific risk assessment |
| Stabilization Ponds | A body of water, usually a pond, used to convert the active organic matter in sludge into inert, harmless material. |
| Standard | That which is established as a measure or model to which others of a similar nature should conform, or technical specification, usually in the form of a document available to the public, drawn up with the consensus or general approval of all interests affected by it, based on the consolidated results of science, technology and experience, aimed at the promotion of optimum community benefits and approved by a body recognized on the national, regional or international level. |
| Standard Operating Procedure (SOP) | A written document that details the method for an operation, analysis, or action with thoroughly prescribed techniques and steps and that is officially approved as the method for performing certain routine or repetitive tasks. |
| Standardization | Establishment of precisely defined characteristics, or precisely defined methods, for future reference, or definition of precise procedures for administering, scoring and evaluating the results of a new method that is under development. |
| Standards | Norms that impose limits on the amount of pollutants or emissions produced. EPA establishes minimum standards, but states are allowed to be stricter. |
| Stockholm Convention on Persistent Organic Pollutants | International treaty to protect human health and the environment from persistent organic pollutants (POPs). It requires the reduction of persistent, bioaccumulating chemicals with adverse health/environmental effects. Governments implementing the Convention are required to take measures to eliminate or reduce the release of POPs into the environment and to consider these characteristics when assessing chemicals. |
| Sub chronic exposure | Multiple or continuous exposures lasting for approximately ten percent of an experimental species lifetime, usually over a three-month period. |
| Sub-chronic | Of intermediate duration, usually used to describe studies or periods of exposure lasting between 5 and 90 days. |
| Substitution Principle | that generally a hazardous substance or process should be replaced by a less hazardous substance or process where possible. Governments applying this principle often provide incentives to stimulate chemical users to continually substitute chemicals with less hazardous alternatives or non-chemical approaches. |
| Surface runoff | Precipitation, snow melt, or irrigation water in excess of what can infiltrate the soil surface and be stored in small surface depressions; a major transporter of non-point source pollutants in rivers, streams, and lakes. |
| Surface water | Any water on the surface of land (i.e., not groundwater). |
