The following words and terms, when used in this chapter, shall have the following meanings, unless the context clearly indicates otherwise.
  (1) Carcinogen--Substances which have been classified for human carcinogenic risk based on the United States Environmental Protection Agency's Weight of Evidence System of Carcinogenicity as:
    (A) Group A--Human Carcinogen;
    (B) Group B--Probable Human Carcinogen; or
    (C) Group C -Possible Human Carcinogen.
  (2) Carcinogen classification--The basis by which substances are classified for human carcinogenic risk based on the United States Environmental Protection Agency's Weight of Evidence System for Carcinogenicity:
    (A) Group A--Human Carcinogen;
    (B) Group B--Probable Human Carcinogen;
    (C) Group C--Possible Human Carcinogen;
    (D) Group D--Not Classifiable as to Human Carcinogenicity; and
    (E) Group E--Evidence of Non-Carcinogenicity for Humans.
  (3) Commercial/industrial land use--Any real property or portion of a property not currently being used for human habitation or for other purposes with a similar potential for human exposure. Examples of commercial/industrial land use include manufacturing; industrial research and development; utilities; commercial warehouse operations; lumber yards; retail gas stations; auto service stations; auto dealerships; equipment repair and service stations; professional offices (lawyers, architects, engineers, real estate, insurance, etc.); medical/dental offices and clinics (not including hospitals); financial institutions; publicly owned office buildings; any retail business whose principal activity is the sale of food or merchandise; personal service establishments (health clubs, barber/beauty salons, mortuaries, photographic studios, etc.); churches (not including churches providing day care or school services other than during normal worship services), and motels/hotels (not including those which allow residence).
  (4) Compliance point--Location(s) selected between the source area(s) and the potential exposure point(s) where concentrations of regulated substances must be at or below the determined target concentrations in media (for example, groundwater, air, soil).
  (5) Direct exposure pathway--An exposure pathway where the point of exposure is at the source, without a release to any other medium.
  (6) Engineering control--Modifications to a site or facility (for example, slurry walls, capping, point of use water treatment) to reduce or eliminate the potential for exposure to a regulated substance.
  (7) Exposure--Subjection of an organism to the action, influence, or effect of a regulated substance (chemical agent) or physical agent. Exposure is quantified as the amount of the agent available at the exchange boundaries (e.g., skin, lungs, gut) and available for absorption by the human body.
  (8) Exposure assessment--The determination or estimation (qualitative or quantitative) of the magnitude, frequency, duration and route of exposure.
  (9) Exposure factors--Those factors used to derive an estimate of the exposure to a regulated substance.
  (10) Exposure pathways--The course a regulated substance takes from a source to an exposed organism. An exposure pathway describes a unique mechanism by which an individual or population is exposed to chemicals at or originating from a leaking storage tank site. Each exposure pathway includes a source, an exposure point, and an exposure route. If the exposure point differs from the source, a transport mechanism must also be present.
  (11) Exposure point--A location where human or environmental receptors can come into contact with regulated substances; also, a location which can be arbitrarily determined for purposes of estimating or measuring the concentration of regulated substances available for exposure.
  (12) Hazard index--The sum of two or more hazard quotients for multiple regulated substances and/or multiple exposure pathways which impact the same target organ or act by the same method of toxicity.
  (13) Hazard quotient--The ratio of a single substance exposure level over a specific time period to a reference dose for that substance derived from a similar exposure period.
  (14) Indirect exposure pathway--An exposure pathway with at least one intermediate release to any media between the source and the point(s) of exposure (for example, chemicals of concern from soil through ground water to the point(s) of exposure).
  (15) Institutional control--Legally binding instruments that the responsible party and the agency may use as part of a corrective action plan to control or eliminate an otherwise viable exposure pathway to ensure that exposure to remaining regulated substances is reduced to a human health and environmentally protective level. Institutional controls may include record notice, land use restrictions, land access restrictions and controls, or other legally binding and practically feasible instrument.
  (16) Maximum contaminant level or MCL--The maximum concentration in water of a regulated substance established by the United States Environmental Protection Agency under Section 141 of the Federal Safe Drinking Water Act.
  (17) Non-carcinogen--Substances shown either through epidemiological studies or through laboratory studies to cause adverse health effects other than cancer.
  (18) Potential beneficial use--The potential use derived from a natural resource (for example, groundwater or surface water) to benefit a user if that resource was not affected by the released regulated substance. This will not consider uses that are unlikely to occur or otherwise extreme circumstances. Groundwater is considered to have a potential beneficial use as a drinking water source if the natural quality of the groundwater is less than 10,000 mg/l total dissolved solids content, yields of usable quantities of water are discharged to wells or springs, or there is a documented use of the groundwater.
  (19) Reasonable maximum exposure estimates--Combination of upper-bound and mid-range exposure factors to be used in dose estimation equations to provide a result which represents an exposure scenario that is both protective and reasonable; not the worst case. Exposure factors as presented in United States Environmental Protection Agency Office of Solid Waste and Emergency Response (OSWER) Directive 9285.6-03, March 25, 1991 or a superseding OSWER directive shall be considered appropriate values for estimation of the reasonable maximum exposure.
  (20) Receptor--Person, structure, utility, surface waters, and water supply wells that are or may be adversely affected by a release.
  (21) Residential land use--Property used for dwellings such as single family houses and multifamily apartments, children's homes and nursing homes. Because of the similarity of exposure potential and the sensitive nature of the potentially exposed population, day care facilities, educational facilities, hospitals, parks and like facilities shall also be considered "residential."
  (22) Risk--The probability that a regulated substance, when released into the environment, will cause an adverse effect in exposed humans or other living organisms.
  (23) Site--Includes all land, regardless of ownership considerations or property boundaries, which is directly affected by the regulated substance.
  (24) Target concentrations--Site-specific and chemical-specific concentration goals for affected media (for example, soil, air, groundwater, surface water) that are protective of human health and safety, and the environment.
  (25) Total excess cancer risk--The upper bound on the estimated excess cancer risk associated with exposure to multiple regulated substances and multiple exposure pathways.

Source Note: The provisions of this §334.202 adopted to be effective November 8, 1995, 20 TexReg 8800; amended to be effective November 23, 2000, 25 TexReg 11442