PE Environmental key terms

Legally enforceable outdoor air concentration limits that the U.S. EPA sets for six criteria pollutants to protect public health with an adequate margin of safety, including sensitive groups such as children and people with asthma.

One of six widespread outdoor air pollutants (carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide) for which EPA must set National Ambient Air Quality Standards under the Clean Air Act.

A geographic region that persistently exceeds a National Ambient Air Quality Standard for a criteria pollutant, triggering stricter permitting and pollution-control requirements and a deadline to attain the standard.

A Clean Air Act permitting program that keeps air quality from worsening in areas already meeting NAAQS by requiring new or modified major sources to install best available control technology and limit emissions.

The most stringent emission limitation achievable for a new or modified major air source, considering energy, environmental, and economic impacts; required under Prevention of Significant Deterioration permitting in attainment areas.

The maximum degree of reduction in hazardous air pollutant emissions that EPA determines is achievable, considering cost and health effects; required for major sources under Clean Air Act Section 112.

Any of 187 toxic air pollutants listed by EPA, such as benzene, formaldehyde, and mercury, that are known or suspected to cause cancer or other serious health effects.

Organic compounds that readily evaporate at room temperature and take part in photochemical reactions forming ground-level ozone; regulated as smog precursors and often measured as total organic carbon.

A mathematical air dispersion model that predicts downwind pollutant concentrations from a continuous point source by assuming pollutant spreads in a normal (Gaussian) distribution horizontally and vertically.

A comprehensive, federally enforceable operating permit required under the Clean Air Act for major stationary air pollution sources, consolidating all applicable emission limits and monitoring requirements into one document.

A Clean Water Act permit program that regulates point-source discharges of pollutants into surface waters by setting effluent limits based on technology and water quality standards.

The maximum amount of a pollutant a water body can receive and still meet water quality standards, allocated among point and nonpoint sources; required for impaired waters under Clean Water Act Section 303(d).

A restriction on the quantity, rate, or concentration of pollutants that may be discharged from a point source, usually expressed as a maximum daily or monthly average allowed by a permit.

A measure of the dissolved oxygen consumed by microorganisms while decomposing organic matter in water over five days at 20 degrees Celsius; used as an indicator of organic pollution strength in wastewater.

The concentration of suspended solid particles, both organic and inorganic, retained by a filter when a water sample is filtered and dried; a common wastewater effluent limit and water quality indicator.

The highest permissible concentration of a contaminant in drinking water delivered to any user of a public water system, set by EPA under the Safe Drinking Water Act as close to health-based goals as feasible.

A discharge of untreated sewage and stormwater into surface waters that occurs when a combined sewer system is overwhelmed by rainfall; regulated through long-term control plans.

A site-specific plan required under NPDES stormwater permits that identifies sources of pollution, describes best management practices, and outlines inspection and training procedures to prevent contaminated runoff.

The federal law governing the generation, transportation, treatment, storage, and disposal of solid and hazardous waste, establishing a cradle-to-grave regulatory system and minimum technical standards for facilities.

A waste that is not specifically listed but exhibits one or more hazardous properties (ignitability, corrosivity, reactivity, or toxicity) as defined by RCRA regulations and confirmed by testing or generator knowledge.

The RCRA principle that waste generators remain responsible for their hazardous waste from the point of generation through final disposal, requiring tracking manifests and permitting of treatment, storage, and disposal facilities.

A laboratory test that simulates leaching of waste in a landfill by tumbling a sample in an acidic extraction fluid; results determine whether a waste exhibits the toxicity characteristic.

A category of widely generated, low-hazard wastes, such as batteries, lamps, mercury thermostats, and some electronics, subject to streamlined handling and disposal requirements instead of full hazardous waste rules.

Liquid that has percolated through solid waste and extracted dissolved or suspended contaminants; landfills collect it with liners and treat it to prevent groundwater pollution.

A non-intrusive investigation of a property's history and current use, including records review, site visit, and interviews, that identifies recognized environmental conditions before property acquisition, conducted according to ASTM standards.

The presence or likely presence of hazardous substances or petroleum products on a property under conditions that indicate an existing release, past release, or material threat of a release.

The investigative standards established by EPA that a prospective purchaser must satisfy to qualify for CERCLA liability protections, typically met by conducting a Phase I Environmental Site Assessment.

The federal Superfund law that authorizes cleanup of hazardous substance releases, establishes liability for responsible parties, and funds remediation when no viable responsible party can be found.

A formal EPA decision document that selects the remedial action for a Superfund site after the remedial investigation and feasibility study, explaining the chosen remedy and its cleanup goals.

A remediation approach that relies on natural physical, chemical, and biological processes, such as dilution, adsorption, and biodegradation, to reduce contaminant concentrations, with long-term monitoring to verify performance.

A liquid-phase contaminant, such as gasoline or heating oil, that is less dense than water and therefore floats on the water table, forming a separate phase that can be recovered by skimming.

An estimate of the daily oral exposure to a contaminant that is likely to be without an appreciable risk of harmful health effects over a lifetime, derived from toxicity studies with uncertainty factors.

A toxicity value that estimates the increased cancer risk per unit of lifetime daily dose of a carcinogen, used with exposure estimates to calculate excess lifetime cancer risk.

The ratio of an estimated exposure dose to a reference dose for a noncarcinogenic chemical; a value above one suggests potential health concern, and values for multiple chemicals are summed as a hazard index.

The route by which a person contacts a contaminant, comprising a source, a transport medium, an exposure point, and an exposure route such as ingestion, inhalation, or dermal contact.

A legally enforceable occupational exposure limit set by OSHA for airborne concentrations of a substance in workplace air, generally expressed as an eight-hour time-weighted average.

An atmospheric concentration of a hazardous substance that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair a person's ability to escape from a dangerous atmosphere.

An OSHA standard governing hazardous waste operations and emergency response, requiring training, medical surveillance, and protective equipment for workers at cleanup sites and emergency releases.

A space large enough for an employee to enter, with limited means of entry or exit, and not designed for continuous occupancy; permit-required spaces need atmospheric testing, ventilation, and an attendant before entry.