glossary

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ACCM – Asbestos-Containing Construction Material – Under California regulations, any manufactured construction material containing more than 0.1% asbestos by weight.

ACM – Asbestos-Containing Material – Any material containing more than 1% asbestos.

AHERA – Asbestos Hazard Emergency Response Act – A federal law enacted in 1986 addressing asbestos-containing materials in public and nonprofit private elementary and secondary schools. AHERA established requirements for asbestos inspections, management plans, response actions, periodic surveillance, and accredited asbestos personnel.

Air Scrubber – A portable HEPA-filtered air-cleaning machine used to remove airborne particles from an enclosed work area. Depending on its setup, an air scrubber may recirculate filtered air within the space or exhaust filtered air outside the containment.

Asbestiform – A mineral growth form characterized by long, thin, flexible fibers that typically occur in bundles and possess characteristics associated with commercial asbestos fibers.

Asbestosis – A chronic, non-cancerous lung disease caused by inhalation of asbestos fibers. The disease involves scarring of lung tissue and may impair breathing.

Asbestos – A group of naturally occurring fibrous silicate minerals. Asbestos fibers are extremely small and may become airborne when asbestos-containing materials are disturbed, damaged, cut, sanded, drilled, demolished, or otherwise handled.

ASTM International – An international standards organization that develops voluntary technical standards and testing methods used in environmental, construction, industrial, and many other fields. The organization was formerly known as the American Society for Testing and Materials.

BAAQMD – Bay Area Air Quality Management District – The regional air-quality agency responsible for regulating air emissions, including asbestos requirements associated with certain demolition and renovation activities within the San Francisco Bay Area.

Bulk Sample – A representative portion of a suspect building material collected for laboratory analysis to determine whether asbestos is present and, when applicable, its percentage.

Cal/OSHA – California’s occupational safety and health program, administered by the Division of Occupational Safety and Health (DOSH). Cal/OSHA establishes and enforces workplace safety requirements, including regulations governing employee exposure to asbestos.

Carcinogen – A substance or agent capable of causing or contributing to the development of cancer.

Category I Non-Friable ACM – Asbestos-containing packings, gaskets, resilient floor coverings, and asphalt roofing products that cannot be crumbled, pulverized, or reduced to powder by hand pressure when dry.

Category II Non-Friable ACM – Non-friable asbestos-containing material that is not classified as Category I. Certain Category II materials may become friable or release asbestos fibers when subjected to demolition, crushing, cutting, grinding, or other significant disturbance.

Chrysotile – A serpentine mineral and the most commonly used commercial form of asbestos. Chrysotile is sometimes referred to as “white asbestos.”

Containment – A temporary enclosure, commonly constructed using polyethylene sheeting, designed to isolate an asbestos work area from surrounding occupied or unaffected portions of a building.

Contaminant – A substance present in an environment where it is not normally expected or present at a concentration that may adversely affect human health or the environment.

Continuous Exposure – Exposure occurring continuously or repeatedly over an extended period of time.

Critical Barriers – Protective barriers used to seal openings into an asbestos work area, including doors, windows, HVAC openings, penetrations, and other pathways through which airborne fibers could migrate.

DOSH – Division of Occupational Safety and Health – The California agency responsible for enforcing occupational safety and health regulations. DOSH administers California’s Cal/OSHA program.

DTSC – California Department of Toxic Substances Control – The California agency responsible for regulating hazardous waste and overseeing certain hazardous-material investigation and cleanup activities.

EPA – U.S. Environmental Protection Agency – The federal agency responsible for protecting human health and the environment and administering numerous environmental regulations, including federal asbestos requirements.

Exposure – Contact with a substance through inhalation, ingestion, skin contact, or another exposure pathway. Exposure may be short-term, intermittent, or long-term.

Friable Asbestos Material – Asbestos-containing material that, when dry, can be crumbled, pulverized, or reduced to powder by hand pressure.

HEPA – High-Efficiency Particulate Air – A filtration classification capable of removing at least 99.97% of airborne particles measuring 0.3 micrometers in diameter.

HEPA Vacuum – A vacuum-cleaning system equipped with HEPA filtration and designed to capture very small particles rather than exhausting them back into the work environment.

HEPA Vacuuming – Cleaning surfaces using a vacuum equipped with HEPA filtration to capture very small particles, including asbestos-containing dust and debris.

Homogeneous Area / Homogeneous Material – An area of suspect building material that is uniform in color, texture, appearance, and application and is reasonably considered to have been installed as the same material. Homogeneous areas are used to determine appropriate representative asbestos sampling locations.

Lockdown – The application of an approved encapsulating or sealing product to surfaces within an asbestos work area after removal and cleaning to help bind residual microscopic fibers or dust.

Miscellaneous Material – Building material other than surfacing material or thermal system insulation that may contain asbestos. Examples include flooring, mastics, roofing products, cement board, wallboard systems, siding, and other manufactured building materials.

Negative-Air Machine – A HEPA-filtered air-filtration device used during asbestos abatement to remove airborne particles and establish negative pressure within a regulated work-area containment.

NESHAP – National Emission Standards for Hazardous Air Pollutants – Federal EPA regulations that include requirements governing asbestos associated with certain demolition and renovation activities, including inspection, notification, handling, removal, and disposal requirements.

Non-Friable ACM – Asbestos-containing material that, when dry, cannot be crumbled, pulverized, or reduced to powder by hand pressure. EPA classifies non-friable ACM as either Category I or Category II.

OSHA – Occupational Safety and Health Administration – The federal agency responsible for establishing and enforcing workplace health and safety standards.

PACM – Presumed Asbestos-Containing Material – Under occupational asbestos regulations, certain thermal system insulation and surfacing materials in older buildings may be presumed to contain asbestos unless that presumption is properly rebutted through inspection, laboratory analysis, or other acceptable documentation.

PCM – Phase Contrast Microscopy – A microscopic analytical method used to count airborne fibers. PCM is not asbestos-specific and cannot distinguish asbestos fibers from other fibers of similar size and shape.

PLM – Polarized Light Microscopy – A laboratory analytical method commonly used to identify and estimate the percentage of asbestos present in bulk building-material samples.

Point Counting – A more precise PLM analytical technique used to determine the percentage of asbestos in certain bulk samples, particularly materials initially reported as containing less than 1% asbestos. Point counting may be used when a more definitive asbestos percentage is required for regulatory or project-planning purposes.

RACM – Regulated Asbestos-Containing Material – A federal regulatory classification that includes friable ACM and certain non-friable asbestos-containing materials that have become, or are likely to become, friable, crumbled, pulverized, or reduced to powder through demolition or renovation activities. Certain Category I materials that are sanded, ground, cut, or abraded may also become RACM.

Regulated Area – A designated work area where asbestos work is being performed or where airborne asbestos concentrations may exceed applicable occupational exposure limits. Access is restricted and specific protective measures are required.

Surfacing Material – Material that is sprayed, troweled, or otherwise applied to a surface for purposes such as acoustical treatment, fireproofing, decoration, or similar applications. Examples may include sprayed fireproofing, acoustical ceiling materials, and certain textured coatings.

TEM – Transmission Electron Microscopy – A highly sensitive analytical method capable of identifying very small asbestos fibers and structures. TEM is commonly used for asbestos air analysis and may also be used for certain bulk, dust, soil, and specialized analyses.

Thermal System Insulation (TSI) – Insulation applied to pipes, fittings, boilers, tanks, ducts, breeching, or other mechanical-system components to prevent heat loss or heat gain. Examples include certain pipe, boiler, tank, and HVAC insulation materials.

Waste Shipment Record / Manifest – Documentation used to track asbestos-containing waste or other regulated waste from its point of generation through transportation to an approved disposal facility. Specific documentation requirements depend on the type and regulatory classification of the waste.

Wet Method – The application of water, generally amended with a wetting agent or surfactant, to asbestos-containing material before and during disturbance or removal to reduce the release of airborne fibers.

Air Sample – A sample of airborne particles collected to help characterize mold spores and other fungal structures present in the air at a particular location and time. Air-sampling results represent conditions during the sampling period and should be interpreted together with visual inspection, moisture measurements, building history, and other available information.

Air Scrubber – A portable HEPA-filtered air-cleaning machine used to remove airborne particles from an enclosed work area. Depending on its configuration, an air scrubber may recirculate filtered air within the area or exhaust filtered air outside the containment.

Allergenic Mold – A general term used for molds capable of producing allergens that may trigger allergic reactions in susceptible individuals. Sensitivity to mold varies considerably from person to person.

Alternaria – A common dark-pigmented fungus frequently found outdoors on plants, soil, and decaying vegetation. Alternaria spores may also be found indoors and may be associated with damp building materials. It is a recognized allergen for some individuals.

Amplification – A condition in which fungal growth or a particular mold type appears elevated indoors compared with expected background conditions. Amplification may indicate an indoor moisture source supporting fungal growth.

Ascospores – Sexual reproductive spores produced by fungi belonging to the phylum Ascomycota. Ascospores are common in outdoor air and may enter buildings through doors, windows, ventilation systems, and normal air exchange.

Aspergillus – A large genus of fungi naturally found in soil, vegetation, dust, and indoor environments. Certain species can grow on damp building materials. Some species may produce allergens, irritants, or mycotoxins, while certain Aspergillus species can cause infections primarily in susceptible or immunocompromised individuals.

Aspergillus/Penicillium-Like Spores – A common laboratory reporting category because many Aspergillus and Penicillium spores cannot be reliably distinguished from one another using routine nonviable spore-trap microscopy.

Aureobasidium – A common environmental fungus that may appear pink, brown, or dark in color. It is frequently associated with damp painted surfaces, wood, window frames, caulking, and other areas subject to condensation or moisture.

Background Sample / Outdoor Control Sample – An outdoor air sample collected during an indoor mold investigation to provide a general comparison with naturally occurring outdoor fungal conditions. Outdoor mold populations can vary substantially with weather, season, vegetation, location, and time of day.

Basidiospores – Sexual spores produced by fungi belonging to the phylum Basidiomycota, which includes mushrooms, puffballs, rusts, and other fungi. Basidiospores are commonly found in outdoor air and frequently enter buildings through normal air exchange.

Bipolaris – A dark-pigmented environmental fungus commonly associated with grasses, plants, and soil. It may occasionally be identified indoors, particularly in damp or water-damaged environments.

Black Mold – A common non-technical or media term used to describe dark or black-colored mold. The term is often associated with Stachybotrys chartarum, although many different mold species can appear black, dark green, brown, or otherwise dark in color. The color of mold does not determine whether it is toxic or how significant its potential health effects may be. Mold should instead be evaluated based on the presence of growth, moisture conditions, extent of contamination, location, and other site-specific factors.

Chaetomium – A fungus commonly associated with chronically wet cellulose-containing materials such as drywall paper, wood, and other water-damaged building products. Its presence indoors can be an indicator of a significant or prolonged moisture condition.

Cladosporium – One of the most common molds found in both indoor and outdoor environments. Outdoor vegetation and soil are major sources. Indoors, Cladosporium may also grow on damp surfaces, window components, HVAC materials, wood, and other substrates.

Condensation – Water that forms when moisture in the air contacts a surface cold enough for water vapor to change into liquid. Persistent condensation can create conditions favorable for mold growth.

Containment – A temporary enclosure, commonly constructed using polyethylene sheeting, designed to isolate a mold-remediation work area from surrounding occupied or unaffected portions of a building.

Critical Barriers – Protective barriers used to seal doors, windows, HVAC openings, penetrations, and other pathways through which dust, mold spores, or other contaminants could migrate from a remediation work area.

Cross-Contamination – The unintended transfer of mold spores, dust, debris, or other contaminants from an affected area to an unaffected area through air movement, foot traffic, equipment, demolition activities, or improper work practices.

Dew Point – The temperature at which air becomes saturated with moisture and condensation begins to form. Dew-point conditions can help explain condensation and moisture accumulation on building surfaces.

Fungi – A biological kingdom that includes molds, mushrooms, yeasts, and other organisms. Fungi obtain nutrients from organic materials and reproduce through spores or other reproductive structures.

Fusarium – A genus of fungi commonly associated with soil and plants. Some species may also grow on very wet or chronically damp building materials and furnishings.

Geotrichum – A group of yeast-like fungi commonly found in soil, water, plants, foods, and other organic materials. Geotrichum may occasionally be identified in indoor environmental samples, particularly where moisture is present.

HEPA – High-Efficiency Particulate Air – A filtration classification capable of removing at least 99.97% of airborne particles measuring 0.3 micrometers in diameter.

HEPA Vacuum – A vacuum-cleaning system equipped with HEPA filtration and designed to capture very small particles rather than exhausting them back into the surrounding environment.

HEPA Vacuuming – Cleaning surfaces using a vacuum equipped with HEPA filtration to remove dust, mold spores, fungal fragments, and other small particles.

Hidden Mold – Mold growth located in concealed or inaccessible areas such as wall cavities, beneath flooring, above ceilings, behind cabinets, beneath carpeting, or within other building assemblies. Hidden mold is commonly associated with an unresolved or historical moisture source.

Hyphae / Hyphal Fragments – Hyphae are thread-like fungal structures that collectively form the vegetative portion of a mold colony. Portions of these structures may break apart and become airborne as hyphal fragments.

Indoor/Outdoor Comparison – The evaluation of indoor mold air-sampling results in relation to outdoor fungal conditions. Interpretation considers mold types, relative concentrations, distribution of spores, inspection findings, and moisture conditions. There is no single indoor/outdoor ratio that automatically determines whether a building has a mold problem.

Microbial Disinfectant / Antimicrobial Product – A product formulated or registered for controlling microorganisms on appropriate surfaces. Such products may be used as part of certain remediation procedures; however, chemical treatment does not substitute for correcting moisture sources and physically removing contaminated materials when removal is necessary.

Memnoniella – A dark-pigmented fungus with environmental characteristics similar to Stachybotrys and commonly associated with wet cellulose-containing materials. Its spores are generally produced in chains rather than the clustered arrangement commonly associated with Stachybotrys.

Moisture Content – The amount of moisture contained within a material. Moisture measurements can assist in identifying damp building materials and conditions that may support mold growth.

Moisture Intrusion – The unwanted entry or accumulation of water or excessive moisture within a building. Common sources include plumbing leaks, roof leaks, exterior drainage problems, foundation seepage, appliance leaks, condensation, and elevated humidity.

Moisture Meter – An instrument used to evaluate moisture conditions in building materials. Depending on the instrument, measurements may be obtained using penetrating pins, non-invasive scanning, or other sensing technology.

Mold – A general term describing microscopic fungi that grow as multicellular filaments. Mold is naturally present indoors and outdoors. Indoor mold growth occurs when sufficient moisture is available on a suitable material or surface. Controlling moisture is the primary means of controlling indoor mold growth.

Mold-Resistant Coating – A coating formulated with ingredients intended to resist fungal growth on the coated surface. Mold-resistant coatings should generally be applied only after the moisture source has been corrected and affected surfaces have been appropriately cleaned and prepared.

MVOC – Microbial Volatile Organic Compound – A volatile chemical produced by microorganisms, including some molds and bacteria, during metabolism. Some MVOCs may contribute to characteristic musty or mold-like odors. A musty odor may indicate microbial activity or moisture but does not identify a particular mold species or concentration.

Mycelium – The interconnected network of fungal hyphae that forms the primary growing structure of a mold colony.

Mycotoxin – A naturally occurring chemical compound that may be produced by certain fungi under particular environmental conditions. The ability to produce mycotoxins varies by fungal species, strain, substrate, moisture level, temperature, and other environmental conditions. Identification of a potentially mycotoxin-producing mold does not by itself establish that significant mycotoxin exposure has occurred.

Negative-Air Machine – A HEPA-filtered air-filtration device configured to establish negative air pressure within a containment so that air tends to move into, rather than out of, the mold-remediation work area.

Non-Porous Material – Material with a relatively impervious surface that does not readily absorb water. Examples include glass, metal, and certain plastics. Depending on conditions, mold contamination on non-porous surfaces can often be removed through appropriate cleaning.

Pathogenic Mold – A general term for fungi capable of causing infection. Serious fungal infections are uncommon in healthy individuals but can be more significant for people with compromised immune systems, certain chronic lung diseases, or other susceptibility factors.

Penicillium – A large genus of fungi commonly found in soil, vegetation, foods, household dust, and indoor environments. Certain species can grow on damp building materials. Penicillium spores are frequently reported together with Aspergillus-like spores during routine nonviable air-sample analysis because of their similar microscopic appearance.

Porous Material – Material containing pores or spaces capable of absorbing water or allowing moisture to penetrate. Examples include drywall, insulation, carpet, ceiling tile, fabric, and certain wood products. Mold contamination may penetrate porous materials, sometimes making effective cleaning difficult.

Post-Remediation Verification (PRV) – An assessment performed after mold remediation to evaluate whether the work area is dry, visibly clean, free of obvious mold growth and remediation debris, and consistent with established completion criteria. Depending on the project, PRV may include visual inspection, moisture measurements, and air or surface sampling.

PPE – Personal Protective Equipment – Protective equipment used to reduce worker exposure to potential hazards. During mold investigation or remediation, PPE may include gloves, protective clothing, eye protection, and appropriate respiratory protection.

Relative Humidity (RH) – The amount of water vapor present in air compared with the maximum amount the air can hold at the same temperature, expressed as a percentage. Persistently elevated indoor relative humidity can contribute to condensation and mold growth.

Remediation – The process of correcting a mold-contamination condition. Remediation generally includes identifying and correcting the moisture source, establishing appropriate work controls, removing or cleaning affected materials, controlling dust and airborne particles, drying the area, and verifying completion.

Source Removal – The physical removal of mold-contaminated materials, dust, debris, or other microbial contamination from a building. Source removal is generally preferable to simply painting over or chemically treating active mold growth.

Spore – A microscopic reproductive structure produced by fungi. Mold spores occur naturally in outdoor and indoor air and can be transported by air currents, people, animals, ventilation systems, and other mechanisms.

Spore-Trap Air Sample – A nonviable air-sampling method in which airborne particles are impacted onto an adhesive collection surface and examined microscopically. Results typically identify and quantify recognizable fungal spores or groups but generally do not determine whether individual spores are viable.

Stachybotrys – A dark-pigmented mold commonly associated with persistently wet cellulose-containing materials such as drywall paper, ceiling tile, and other water-damaged building products. Certain strains can produce mycotoxins under appropriate environmental conditions. Stachybotrys is frequently referred to in the media as “black mold,” although many other molds can also appear black or dark in color.

Surface Sample – A sample collected directly from a surface to determine whether fungal structures are present or to help identify the type of fungal growth. Common surface-sampling methods include tape lifts and swabs.

Swab Sample – A surface sample collected by rubbing a sterile swab across a suspect surface and submitting the swab for laboratory analysis.

Tape-Lift Sample – A surface-sampling technique in which transparent adhesive material is placed directly against a suspect area to collect fungal structures for microscopic examination and identification.

Thermal Imaging / Infrared Imaging – The use of an infrared camera to identify surface-temperature differences that may indicate moisture-related conditions, insulation deficiencies, air leakage, or other building anomalies. Thermal imaging does not directly detect mold or moisture and suspected conditions should be confirmed using appropriate inspection methods and moisture-testing equipment.

Toxigenic Mold / “Toxic Mold” – Toxigenic mold is a more technically appropriate term for fungal species capable of producing mycotoxins under certain environmental conditions. “Toxic mold” is a commonly used public and media term but can be misleading because the mold itself is not automatically toxic, and the presence of a potentially toxigenic species does not establish that mycotoxins are being produced or that harmful exposure has occurred.

Trichoderma – A genus of fungi commonly found in soil and decaying organic material. Certain species may grow on damp cellulose-containing building materials, particularly where significant moisture is present.

Ulocladium – A dark-pigmented fungal group historically reported in environmental samples and commonly associated with soil, vegetation, and damp building materials. Some organisms historically classified as Ulocladium have subsequently been reclassified through modern fungal taxonomy.

Visible Mold Growth – Fungal growth that can be observed on a surface without laboratory analysis. Visible mold typically indicates that moisture has been or is currently available to support growth.

Water-Damaged Building Material – Building material that has been wetted by leakage, flooding, condensation, plumbing failure, appliance malfunction, exterior water intrusion, or another moisture source. Wet building materials should be dried promptly to reduce the potential for microbial growth.

Abatement – Measures designed to permanently eliminate lead-based paint hazards. Lead abatement is different from ordinary renovation, repair, or painting because the specific intent of abatement is permanent lead-hazard reduction.

Air Scrubber – A portable HEPA-filtered air-cleaning machine used to remove airborne particles from an enclosed work area. Depending on its configuration, an air scrubber may recirculate filtered air or exhaust filtered air outside the containment.

Blood Lead Level (BLL) – The concentration of lead measured in a person's blood, typically reported in micrograms per deciliter (µg/dL). Blood lead testing is performed by healthcare professionals and laboratories and is used to evaluate lead exposure.

Blood Lead Reference Value (BLRV) – CDC currently uses a blood lead reference value of 3.5 µg/dL to identify children ages 1–5 whose blood lead levels are higher than those of most U.S. children. The BLRV is not a threshold separating safe from unsafe exposure; CDC states that no safe blood lead level in children has been identified. CDC

CDPH – California Department of Public Health – The California agency responsible for numerous public-health programs, including the Childhood Lead Poisoning Prevention Branch and certification of lead-related construction professionals.

Child-Occupied Facility – A building, or portion of a building, constructed before 1978 and regularly visited by children under six years of age, such as certain childcare facilities, preschools, and kindergarten classrooms, as defined under applicable EPA regulations.

Cleaning Verification – A procedure used under EPA's Renovation, Repair and Painting (RRP) Rule to verify that a renovation work area has been adequately cleaned. Cleaning verification is not the same as a formal lead clearance examination involving laboratory analysis of dust-wipe samples.

Clearance Examination / Lead Clearance – An evaluation conducted following lead-hazard reduction or abatement activities to determine whether the work area meets applicable completion criteria. Clearance generally includes a visual assessment and collection of dust-wipe samples for laboratory analysis. In California, paid lead clearance inspections in residential or public buildings generally must be conducted by an appropriately CDPH-certified professional. California Department of Public Health

Containment – A temporary enclosure or barrier system used to isolate a lead work area from surrounding occupied or unaffected portions of a building and prevent the migration of lead-containing dust and debris.

Critical Barriers – Protective barriers used to seal HVAC openings, doors, windows, penetrations, and other pathways through which lead-containing dust or debris could migrate from a work area.

D-Lead Wipes – A commercial brand of disposable cleaning wipes formulated to help remove lead and other heavy-metal contamination from hands and surfaces. Similar lead-specific cleaning products are also available. These products do not replace required lead-safe work practices or clearance procedures.

Deteriorated Paint – Paint or another surface coating that is peeling, chipping, chalking, cracking, damaged, or otherwise separating from the substrate. Deteriorated lead-based paint can contribute to lead-contaminated dust and paint chips.

Dust-Lead Action Level (DLAL) – Federal EPA – EPA's current federal post-abatement dust-lead action levels are 5 µg/ft² for floors, 40 µg/ft² for window sills, and 100 µg/ft² for window troughs. These replaced EPA's former dust-lead clearance levels and became applicable beginning January 12, 2026 in EPA-administered lead-based paint programs. US EPA

Dust-Lead Reportable Level (DLRL) – Federal EPA – EPA's current federal standard considers dust lead a hazard at any reportable level detected by an EPA-recognized laboratory during a regulated lead risk assessment or lead hazard screen. EPA adopted the term “dust-lead reportable level” to replace the previous term “dust-lead hazard standard.” US EPA

Dust Wipe Sample – A sample collected by wiping a measured surface area with an approved wipe and submitting it to a laboratory for lead analysis. Dust-wipe results are normally reported as micrograms of lead per square foot (µg/ft²).

EPA – U.S. Environmental Protection Agency – The federal agency responsible for administering numerous environmental regulations, including lead-based paint disclosure, RRP requirements, lead-based paint activities, and drinking-water regulations.

First-Draw Water Sample – A drinking-water sample collected after water has remained unused in the plumbing system for a specified period, typically several hours. First-draw sampling can help evaluate lead contributed by plumbing fixtures, solder, pipes, and other components.

Friction Surface – A painted surface that is subject to abrasion or friction, such as certain windows and doors. Repeated movement can generate lead-contaminated paint chips or dust when lead-containing coatings are present.

HEPA – High-Efficiency Particulate Air – A filtration classification capable of removing at least 99.97% of airborne particles measuring 0.3 micrometers in diameter.

HEPA Vacuum – A vacuum-cleaning system equipped with HEPA filtration and designed to capture very small particles, including lead-containing dust, rather than exhausting them back into the surrounding environment.

HUD – U.S. Department of Housing and Urban Development – The federal agency responsible for housing programs and regulations, including additional lead-based paint requirements affecting certain federally assisted housing.

Impact Surface – A building surface that is repeatedly struck or contacted by another surface or object, potentially causing paint deterioration and generating chips or dust.

Interim Controls – Temporary or ongoing measures designed to reduce exposure to lead-based paint hazards without permanently eliminating all lead-based paint. Examples may include specialized cleaning, paint stabilization, repairs, and controlling lead-contaminated soil or dust.

Lead – A naturally occurring metallic element with the chemical symbol Pb and atomic number 82. Lead has historically been used in paint, plumbing, gasoline, batteries, industrial products, and many other applications. Lead is toxic, and exposure can adversely affect multiple organ systems.

Lead Abatement – Work specifically designed to permanently eliminate lead-based paint hazards. Abatement may involve paint removal, component replacement, enclosure, encapsulation, soil removal, or other approved permanent hazard-control methods.

Lead-Based Paint (LBP) – Paint or other surface coating containing lead at or above 1.0 milligram per square centimeter (mg/cm²) or 0.5% by weight, equivalent to 5,000 parts per million (ppm). This definition is used under federal regulations and California Title 17. US EPA

Lead-Based Paint Hazard – A condition involving lead-based paint, lead-contaminated dust, or lead-contaminated soil that can result in lead exposure. Examples may include deteriorated lead-based paint and lead-based paint on certain friction, impact, or chewable surfaces.

Lead-Containing Paint – A general term describing paint in which lead is detected. Paint may contain measurable lead at concentrations below the regulatory definition of “lead-based paint.” Paint below 0.5% lead should not automatically be described as lead-free, and occupational requirements may still apply when work generates employee lead exposure.

Lead-Contaminated Dust – California – Under current California Title 17 regulations, lead-contaminated dust is dust containing lead at or above 10 µg/ft² on interior floors, 100 µg/ft² on interior horizontal surfaces, or 400 µg/ft² on exterior floors and horizontal surfaces. California Department of Public Health

Lead-Contaminated Soil – California – California Title 17 defines lead-contaminated soil as bare soil containing 400 ppm or more in children's play areas and 1,000 ppm or more in other areas. Separate health-based screening levels may be substantially lower. California Department of Public Health

Lead in Construction – Cal/OSHA – California's occupational lead standard applies to construction work in which employees may be exposed to lead, including construction, alteration, repair, painting, demolition, and related activities. California substantially strengthened this standard effective January 1, 2025. CalDIR

Lead Occupational Action Level – California – Under California's current construction lead standard, the action level is 2 micrograms of lead per cubic meter of air (2 µg/m³) calculated as an 8-hour time-weighted average. Reaching the action level triggers additional employer requirements such as exposure monitoring and medical surveillance. CalDIR

Lead Occupational Permissible Exposure Limit (PEL) – California – Cal/OSHA's current lead PEL for construction is generally 10 µg/m³ as an 8-hour time-weighted average. California's standard is more protective than the federal OSHA construction lead PEL. CalDIR

Lead Paint – A general term commonly used to describe paint containing lead. For regulatory purposes, the more precise term lead-based paint should be used when the coating meets the applicable regulatory threshold.

Lead Poisoning / Lead Exposure – Lead can accumulate in the body and affect the nervous system, kidneys, cardiovascular system, blood-forming system, and other organs. Young children are particularly vulnerable because their bodies and nervous systems are developing. Lead exposure can occur through ingestion or inhalation of contaminated dust, paint, soil, water, or other sources. No safe blood lead level in children has been identified.

Lead Risk Assessment – An on-site investigation designed to determine whether lead-based paint hazards are present and, when hazards are identified, recommend appropriate controls. A risk assessment may include visual inspection and testing of paint, dust, soil, and other potential lead sources.

Lead-Safe Certified Firm – EPA RRP – A renovation firm certified by EPA to perform work regulated by the Renovation, Repair and Painting Rule. EPA RRP firm certification is generally valid for five years. US EPA

Lead Soil Hazard Standard – Federal EPA – EPA's existing residential soil-lead hazard standards are 400 ppm in children's play areas and an average of 1,200 ppm in other bare-soil areas of the yard. These regulatory hazard levels should not be confused with lower health-based screening levels used for environmental investigations.

Lead Soil Screening Level – California DTSC – The California Department of Toxic Substances Control currently uses 80 mg/kg (ppm) as its default residential soil screening level for lead. A screening level is an investigation tool and is not the same as California's Title 17 definition of lead-contaminated soil. Department of Toxic Substances Control

Lead in Drinking Water Action Level – EPA – Through October 31, 2027, EPA's Lead and Copper Rule uses 15 µg/L (15 ppb) as the lead action level for public water systems. Under the Lead and Copper Rule Improvements, the action level is scheduled to decrease to 10 µg/L (10 ppb) beginning November 1, 2027. An action level is a regulatory trigger for public water systems and should not be interpreted as a health-based “safe” concentration. US EPA

Lead in Drinking Water Maximum Contaminant Level Goal (MCLG) – EPA's health-based maximum contaminant level goal for lead in drinking water is zero, reflecting the goal of minimizing lead exposure.

Lead-Based Paint Inspection – A surface-by-surface investigation to determine the presence and location of lead-based paint within a building. An inspection generally uses XRF testing and/or laboratory analysis of paint-chip samples but does not necessarily evaluate whether the identified paint currently constitutes a lead hazard.

Negative-Air Machine – A HEPA-filtered air-filtration device configured to establish negative air pressure within a containment, helping prevent lead-containing dust from migrating into surrounding areas.

Paint Chip Sample – A physical sample of paint or other surface coating collected and submitted to a laboratory to determine its lead concentration, typically reported as percentage by weight, mg/kg, or ppm.

Paint Stabilization – An interim-control method used to address deteriorated painted surfaces. Work may include correcting the cause of deterioration, safely removing loose material, preparing surfaces using lead-safe practices, and applying a new protective coating.

PPM – Parts Per Million – A unit commonly used to report lead concentration by weight. For solid materials, 1 ppm is generally equivalent to 1 mg/kg or 1 µg/g.

PPE – Personal Protective Equipment – Equipment used to reduce worker exposure to hazards. Depending on the work activity, PPE for lead work may include gloves, protective clothing, eye protection, footwear, and appropriate respiratory protection.

RRP – Renovation, Repair and Painting – EPA's program governing certain renovation, repair, and painting activities that disturb painted surfaces in pre-1978 housing and child-occupied facilities.

Renovation, Repair and Painting (RRP) Rule – EPA regulations requiring lead-safe work practices and certified firms and renovators for covered work in pre-1978 housing and child-occupied facilities. The rule generally applies when more than 6 square feet of painted surface per room indoors or 20 square feet outdoors is disturbed, as well as certain other activities such as window replacement, subject to applicable exemptions. US EPA

Risk Assessment – See Lead Risk Assessment.

STLC – Soluble Threshold Limit Concentration – A California hazardous-waste criterion determined using the Waste Extraction Test (WET). For lead, the STLC regulatory threshold is 5.0 mg/L. A waste may be classified as hazardous in California when applicable regulatory criteria are exceeded. Department of Toxic Substances Control

Target Housing – Generally, housing constructed before 1978 that is subject to federal lead-based paint requirements, with certain regulatory exemptions.

TCLP – Toxicity Characteristic Leaching Procedure – A federal laboratory procedure used to evaluate whether waste exhibits the toxicity characteristic for hazardous-waste purposes. The federal TCLP regulatory threshold for lead is 5.0 mg/L.

TTLC – Total Threshold Limit Concentration – A California hazardous-waste criterion based on the total concentration of certain substances in a waste. California's TTLC threshold for lead is 1,000 mg/kg. Department of Toxic Substances Control

Visual Assessment – A visual inspection of painted surfaces and surrounding areas for conditions such as deteriorated paint, visible dust or debris, damaged components, or other potential lead hazards. A visual assessment alone cannot determine whether paint contains lead.

Waste Extraction Test (WET) – A California laboratory extraction procedure used to determine a waste's Soluble Threshold Limit Concentration (STLC).

XRF – X-Ray Fluorescence Analyzer – A portable instrument used by qualified lead professionals to measure lead in painted surfaces without removing a physical paint sample. Results are commonly reported in milligrams of lead per square centimeter (mg/cm²).

µg – Microgram – One millionth of a gram.

µg/dL – Micrograms per Deciliter – A unit commonly used to report blood lead concentrations.

µg/ft² – Micrograms per Square Foot – A surface-loading unit commonly used to report lead concentrations in dust-wipe samples.

µg/L – Micrograms per Liter – A concentration unit commonly used for lead in drinking water. In water, 1 

µg/L is approximately equivalent to 1 part per billion (ppb).

µg/m³ – Micrograms per Cubic Meter – A concentration unit used to report airborne lead concentrations for occupational exposure assessment.

mg/cm² – Milligrams per Square Centimeter – A surface-area concentration commonly used for XRF lead-paint measurements. 1.0 mg/cm² is one of the regulatory thresholds defining lead-based paint.

mg/kg – Milligrams per Kilogram – A concentration by weight equivalent to parts per million (ppm) for solid materials.

ft² – Square Foot – A unit of area measuring 12 inches by 12 inches. Dust-lead surface concentrations are commonly expressed in µg/ft².