| C | Carbon |
| C and D Landfill | Construction and Demolition Landfill |
| C₂H₅OH | Ethanol |
| C5+ | Pentanes plus |
| C6H5 | Benzene |
| CA | Compliance Assistance; Cooperative Agreement |
| CA010 | RFA Initiation |
| CA050 | RFA Completed |
| CA060 | Notice of Contamination |
| CA070NO | Determination of Need for an Investigation - Investigation is Not Necessary |
| CA070YE | Determination of Need for an Investigation - Investigation is Necessary |
| CA075HI | CA Prioritization - Facility; Area was Assigned a High Corrective Action Priority |
| CA075LO | CA Prioritization - Facility; Area was Assigned a Low Corrective Action Priority |
| CA075ME | CA Prioritization - Facility; Area was Assigned a Medium Corrective Action Priority |
| CA100 | Investigation Imposition |
| CA110 | Investigation Workplan Received |
| CA120 | Investigation Workplan Modification Requested by Agency |
| CA140 | Investigation Workplan Notice of Deficiency Issued |
| CA150 | Investigation Workplan Approved |
| CA155 | Investigation Supplemental Information Requested by Agency |
| CA160 | Investigation Supplemental Information Received |
| CA170 | Investigation Supplemental Information Deemed Satisfactory |
| CA180 | Investigation Implementation Begun |
| CA190 | Investigation Report Received |
| CA195 | Investigation Progress Reports Received |
| Ca(2+) | calcium |
| CA200 | Investigation Complete |
| CA210OT | CA Responsibility Referred to a Non-RCRA Authority - CA Referred to Another Non-RCRA Authority |
| CA210SF | CA Responsibility Referred to a Non-RCRA Authority - CA Referred to CERCLA |
| CA225IN | Stabilization Measures Evaluation - Facility is not Amenable to Stabilization Activity (Lack of Data) |
| CA225NF | Stabilization Measures Evaluation - Facility is not Amenable to Stabilization Activity at this Time |
| CA225NR | Stabilization Measures Evaluation - Facility is not Amenable to Stabilization Activity (Other Reason) |
| CA225YE | Stabilization Measures Evaluation - Facility is Amenable to Stabilization Activity |
| CA250 | CMS Imposition |
| CA260 | CMS Workplan Received |
| CA270 | CMS Workplan Modification Requested by Agency |
| CA300 | CMS Workplan Approved |
| CA305 | CMS Supplemental Information Requested by Agency |
| CA310 | CMS Supplemental Information Received |
| CA320 | CMS Supplemental Information Deemed Satisfactory |
| CA330 | CMS Implementation Begun |
| CA340 | CMS Report Received |
| CA345 | CMS Progress Reports Received |
| CA350 | CMS Complete |
| CA370 | Petition For No Further Action Receipt Date |
| CA375 | Interim Decision for No Further Action |
| CA380 | Date For Public Notice On Proposed Remedy |
| CA400 | Remedy Decision |
| CA450 | Corrective Measures Design Approved |
| CA500 | CMI Workplan Approved |
| CA510 | Determination of Technical Impracticability |
| CA550NR | Remedy Construction - No Remedy Constructed |
| CA550RC | Remedy Construction - Remedy Constructed |
| CA555 | Remedy Construction Deferral Expiration |
| CA600 | Stabilization Measures Decision |
| CA600EC | Stabilization Measures Implemented - Exposure Control by Barrier and/or Institutional Control |
| CA600GW | Stabilization Measures Implemented - Groundwater Extraction and Treatment |
| CA600OT | Stabilization Measures Implemented - Other Activity |
| CA600SR | Stabilization Measures Implemented - Source Removal and/or Treatment |
| CA650 | Stabilization Construction Completed |
| CA650EC | Stabilization Construction Completed - Exposure Control by Barrier and/or Institutional Control |
| CA650GW | Stabilization Construction Completed - Groundwater Extraction and Treatment |
| CA650OT | Stabilization Construction Completed - Other Activity |
| CA650SR | Stabilization Construction Completed - Source Removal and/or Treatment |
| CA725IN | Current Human Exposures Under Control - More Information Needed |
| CA725NO | Current Human Exposures Under Control - Not Under Control |
| CA725YE | Current Human Exposures Under Control - Under Control |
| CA750IN | Groundwater Releases Controlled Determination - More Information Needed |
| CA750NO | Groundwater Releases Controlled Determination - Unacceptable Migration of GW is Observed; Expected |
| CA750YE | Groundwater Releases Controlled Determination - Migration of Contaminated GW is Under Control |
| CA770GW | Engineering Controls Established - Groundwater Control |
| CA770NG | Engineering Controls Established - Non-groundwater Control |
| CA772EP | Institutional Controls Established - Enforcement and Permit Tools |
| CA772GC | Institutional Controls Established - Governmental Control |
| CA772ID | Institutional Controls Established - Information Device |
| CA772PR | Institutional Controls Established - Proprietary Control |
| CA780GW | Engineering Controls Terminated - Groundwater Control |
| CA780NG | Engineering Controls Terminated - Non-groundwater Control |
| CA782EP | Institutional Controls Terminated - Enforcement & Permit Tools |
| CA782GC | Institutional Controls Terminated - Governmental Control |
| CA782ID | Institutional Controls Terminated - Informational Device |
| CA782PR | Institutional Controls Terminated - Proprietary Control |
| CA800NO | Ready for Anticipated Use - No |
| CA800YE | Ready for Anticipated Use - Yes |
| CA900CR | CA Performance Standards Attained - Controls Required |
| CA900NC | CA Performance Standards Attained - No Controls Are Necessary |
| CA999 | Corrective Action Process Terminated |
| CA999NF | Corrective Action Process Terminated - No Further Action |
| CA999RM | Corrective Action Process Terminated - Remedial Activities Completed |
| CAA | Clean Air Act |
| CAAP Discharge | Concentrated Aquatic Animal Production Discharge |
| CaCO₃ | Limestone |
| CACO3 Equivalent | Calcium Carbonate Equivalent |
| CAD | Cold Air Damming |
| CADDIS | Causal Analysis/Diagnosis Decision Information System |
| CAFO | Concentrated Animal Feeding Operation |
| CAFO Discharge | Concentrated Animal Feeding Operation Discharge |
| CAFOs | Concentrated Animal Feeding Operations |
| CAG | Community Advisory Groups; Cumulative Assessment Group |
| CAIR | Clean Air Interstate Rule |
| CAL | Calibration Standard |
| CAL SYSTEM | COMPUTER-ASSISTED LOCATER SYSTEM |
| California EPA REL | California EPA's Reference Exposure Level |
| CAM Plant | Crassulacean Acid Metabolism Plant |
| CAMD | Clean Air Markets Division |
| CAMU | Corrective Action Management Unit |
| CAMUs | Corrective Action Management Units |
| CAO | Corrective Action Order; Lime |
| CAP | Community Assistance Panel; Corrective Action Plan; COST ALLOCATION PLAN; Criteria Air Pollutant |
| CAPs | Criteria Air Pollutants |
| CAR | Constitutive Androstane Receptor |
| CAR SYSTEM | COMPUTER-ASSISTED RETRIEVAL SYSTEM |
| CARB 435 | California Air Resources Board analytical method 435 |
| CARC | Chemical Agent Resistant Coating |
| CART | Classification and Regression Tree |
| CAS | Chemical Abstract Service; Chemical Abstracts Services Registry Number |
| CAS No. | Chemical Abstracts Service Registry Number |
| CAS Number | Chemical Abstract Service Number |
| CASRN | CAS Registry Number; Chemical Abstracts Service Number |
| CATEX | Categorical Exclusion |
| CATV | Cable TV |
| CAV | Constant Air Volume System |
| CBA | Cost Benefit Analysis |
| CBI | Confidential Business Information |
| CBL | Convective Boundary Layer |
| CBM | Coalbed methane |
| CBOB-Summer | Summer Conventional Blendstock for Oxygenate Blending |
| CBOB-Winter | Winter Conventional Blendstock for Oxygenate Blending |
| CBOD | Carbonaceous Biochemical Oxygen Demand |
| CBP | U.S. Customs and Border Protection |
| CBPR | Community-Based Participatory Research |
| CBR Attack | Chemical, Biological; Radiological Attack |
| CBSA | Core-Based Statistical Area |
| CC | Catalytic Converter; Certificate of Conformity |
| CC14 | Carbon Tetrachloride |
| CCA | Chromated Copper Arsenate; Community Choice Aggregation |
| CCC | Continuing Calibration Check; Criterion Continuous Concentration |
| CCCD | Centralized Combustion Control Device |
| CCDS | Case Conclusion Data Sheet |
| CCh | Carbachol |
| CCI | Chemical Characterization and Informatics |
| CCL | Construction Completion List |
| CCN | Cloud Condensation Nucleus |
| CCPs | Commercial Chemical Products |
| CCR Landfill | Coal Combustion Residuals Landfill |
| CCR Surface Impoundment | Coal Combustion Residuals Surface Impoundment |
| CCR Unit | Coal Combustion Residuals Unit |
| CCS | Carbon Capture and Sequestration; Carbon Capture and Storage |
| CCSS | Central Client Server Systems |
| CCT | Clean Coal Technology |
| CCU | Carbon Capture and Usage |
| CCV | Continuing Calibration Verification |
| Cd | Cadmium; COMPACT DISK; Consent Decree |
| C&D Debris | Construction and Demolition Debris |
| C&D Materials | Construction and Demolition Materials |
| C&D Wood | Construction and Demolition Wood |
| CDC | Centers for Disease Control and Prevention |
| CDD | Cooling Degree Day |
| CDF | confined disposal facility; Cumulative Distribution Function |
| CDFs | Chlorinated Dibenzofurans |
| CD-I | COMPACT DISK--INTERACTIVE |
| CDI | Case Development Inspection |
| cDNA | Complementary DNA |
| CDX | Central Data Exchange |
| CE | Capillary Electrophoresis; Capture Efficiency; conditionally exempt generators; Control Efficiency; Control equipment table; cost effectiveness |
| CEA | cost-effectiveness analysis |
| CEC | Contaminant of Emerging Concern |
| CEE | Comprehensive Environmental Evaluation |
| CEI | Compliance Evaluation Inspection |
| CEL | Comparative Effect Level |
| CEM | Contagious Equine Metritis; Continuous Emission Monitoring |
| CEMS | Continuous Emission Monitoring System; Continuous Emissions Monitoring System |
| Central AHU | Central Air Handling Unit |
| CEPPO | Chemical Emergency Preparedness and Prevention Office |
| CERCLA | Comprehensive Environmental Response, Compensation & Liability Act; Comprehensive Environmental Response Compensation and Liability Act Criminal Litigation |
| CERCLIS | Comprehensive Environmental Response, Compensation and Liability Information System |
| CERCLIS 3 | Comprehensive Environmental Response, Compensation, and Liability Information System 3 |
| CERS | Consolidated Emissions Reporting Schema |
| CERT | Continuous Emission Reduction Technology |
| Certified NTDF | Certified Non-Transportation 15 ppm Distillate Fuel |
| CESQG | Conditionally Exempt Small Quantity Generators |
| CESQGs | Conditionally Exempt Small Quantity Generator |
| CF | Capacity Factor |
| CFB | Circulating Fluidized Boiler |
| CFC | Chlorofluorocarbon |
| CFCs | Chlorofluorocarbons |
| CFL | Compact Fluorescent Lamp |
| CFLs | Compact fluorescent lamps |
| CFM | Chlorofluoromethanes; Cubic Feet per Minute |
| CFR | The Code of Federal Regulations |
| cfu | colony forming unit |
| CG | Character generator |
| CGI | common gateway interface |
| CGL Insurance | Comprehensive General Liability Insurance |
| CH₃Br | Methyl Bromide |
| CH3CCl3 | Methyl Chloroform |
| CH₄ | Methane |
| CHAD | Consolidated Human Activity Database |
| ChAT | Choline Acetyltransferase |
| ChE | Cholinesterases |
| Chl | Chlorophylls |
| Chol | Cholesterol |
| CHP | Chemical Hygiene Plan; Combined Heat and Power Plant; Combined Heat and Power Unit |
| Chr | Chrysene |
| Chronic RfC | Chronic Reference Concentration |
| Chronic RfD | Chronic Reference Dose |
| CI | Cation; Confidence Interval; Curie |
| CIM | COMPUTER INPUT MICROFILM |
| CIMS | Chemical Ionization Mass Spectrometry |
| CIO | Chief Information Officer |
| CIP Plan | Capital Improvement Program Plan |
| CISS | Chemical Information Submission System |
| CISWI | Commercial and Industrial Solid Waste Incinerator |
| Citrus HLB | Citrus Huanglongbing |
| CIU | Categorical Industrial User |
| CL | Climatological Outlook |
| Clay Ceramics Metal HAP | Clay Ceramics Metal Hazardous Air Pollutant |
| CLOD | Coralline Lethal Orange Disease |
| Closed-Loop Geothermal Heat Pump System | Heat Pump |
| Closing RPM | Closing Revolutions per Minute |
| CLP | Contract Laboratory Program |
| CM Assay | Cytosensor Microphysiometer Assay |
| CMAQ Modeling System | Community Multi-scale Air Quality Modeling System |
| CMBO | Chloromethylbutenone |
| CMC | Criterion Maximum Concentration |
| CMF | Coagulation-Assisted Micro-Filtration |
| CMI | Corrective Measure Implementation |
| CMPU | Chemical Manufacturing Process Unit |
| CMS | Conservation management system; Corrective Measure Study |
| CMSA | Consolidated Metropolitan Statistical Area |
| CMYK | Cyan, Magenta, Yellow and Black |
| CN,A | Cyanide A |
| CNG | Compressed Natural Gas |
| CNS | Central Nervous System |
| CNS Irritation | Cortical Excitability |
| CNT | Carbon Nanotube; Contract |
| CO | Carbon Monoxide; Change Order; Contracting Officer |
| CO₂ | Carbon Dioxide |
| CO2 Offset Requirements | Carbon Dioxide Offset Requirements |
| CO2 Stream | Carbon Dioxide Stream |
| CO₂e | Carbon Dioxide Equivalent |
| COA | Corresponding Onshore Area |
| Coating Application VOC Content | Coating Application Volatile Organic Compound Content |
| COC | Chain of Custody; Contaminant of Concern; Contaminants of Concern |
| COD | Chemical Oxygen Demand |
| COFF | CUTOFF |
| COH | Coefficient of Haze |
| COI | Conflict of Interest; cost-of-illness method |
| Cold Temperature FTP | Cold Temperature Federal Emission Test Procedure |
| COM | COMPUTER OUTPUT MICROFILM |
| Commercial HMIWI | Commercial Hospital/Medical/Infectious Waste Incinerator |
| Comp Tox | Computational Toxicology |
| COMS | Continuous Opacity Monitoring System |
| Consequential LCA | Consequential Life Cycle Assessment |
| Consolidated MCAN | Consolidated Microbial Commercial Activity Notice |
| Consolidated PMN | Consolidated Premanufacture Notice |
| Continuous HMIWI | Continuous Hospital/Medical/Infectious Waste Incinerator |
| Continuous PVCPU Operation | Continuous Polyvinyl Chloride and Copolymers Production Process Unit Operation |
| CONTRACTOR | Kr |
| Controlled HAP Emission | Controlled Hazardous Air Pollutant Emission |
| Controlled Organic HAP Emission | Controlled Organic Hazardous Air Pollutant Emission |
| COOP | Continuity of Operations Plan |
| COP | Coefficient of performance; Conference Of Parties |
| COPC | Constituent of Potential Concern; Contaminant of Potential Concern |
| COPD | Chronic Obstructive Pulmonary Disease |
| COPEC | Contaminant of Potential Ecological Concern |
| Copper Foundry HAP | Copper Foundry Hazardous Air Pollutant |
| COR | Copy of Record |
| COTS Item | Commercially Available Off-the-Shelf Item |
| COV | Coefficient of variation |
| CPA | Cleaner Production Assessment; Cyclopiazonic Acid |
| CPCA | Core Program Cooperative Agreement |
| CPDS | Certified Product Data Sheet |
| CPE | Customer Premises Equipment |
| CPG | Comprehensive Procurement Guidelines |
| CPI | Consumer Price Index |
| CPK | Creatine Phosphokinase |
| CPM | Condensable Particulate Matter; counts per minute |
| CPMS | Continuous Parameter Monitoring System |
| CPT | cone penetrometer testing |
| CPU | CENTRAL PROCESSING UNIT |
| CQA | Construction Quality Assurance |
| CR | Community Relations; Complex resistivity |
| CRA | Comparative Risk Assessment; cumulative risk assessment |
| CRC | Community Relations Coordinator |
| CRD | Chemical Relational Database |
| CRDL | Contract - Required Detection Limit |
| CREE | Carbon-Related Exhaust Emissions |
| CREP | Conservation Reserve Enhancement Program |
| CRF | Capital Recovery Factor |
| CRM | Certified Reference Material |
| cRNA | Complementary RNA |
| CROMERR | Cross-Media Electronic Reporting Rule |
| CROP | Consolidated Rules of Practice |
| CRP | Child Resistant Packaging; Community Relations Plan; Conservation Reserve Program |
| CRQL | Contract - Required Quantitation Limit |
| CRT | Cathode Ray Tube |
| CRT Collector | Cathode Ray Tube Collector |
| CRT Exporter | Cathode Ray Tube Exporter |
| CRT Glass Manufacturer | Cathode Ray Tube Glass Manufacturer |
| CRT Processing | Cathode Ray Tube Processing |
| CRVD | Cerebrovascular Disease |
| Cs-137 | Cesium-137 |
| CSA | Combined Statistical Area |
| CSA (Allowance) | Critical Stock Allowance |
| CSA Holder | Critical Stock Allowance Holder |
| CSF | Cancer Slope Factor; Confidential Statement of Formula |
| CSGWPP | Comprehensive State Groundwater Protection Program |
| CSI | Common Sense Initiative |
| CSM | Conceptual Site Model |
| CSO | Combined Sewer Overflow |
| CSS | Cascading Style Sheets; Combined Sewer System |
| CT calculations | Residual Disinfectant Concentration (regulatory) |
| CTE | Central tendency exposure |
| CTG | Control Technique Guidelines |
| CTS | Carpal Tunnel Syndrome |
| CUA | Critical Use Allowance |
| CUA Holder | Critical Use Allowance Holder |
| CUI | Controlled Unclassified Information |
| CUI Type Basic | Controlled Unclassified Information Type Basic |
| CUI Type Specified | Controlled Unclassified Information Type Specified |
| CUI//ADPO | Administrative Proceedings - Basic |
| CUI//BARG | Collective Bargaining - Basic |
| CUI//EMGT | Emergency Management - Basic |
| CUI//FNC | General Financial Information - Basic |
| CUI//ISVI | Information Systems Vulnerability Information - Basic |
| CUI//LCOMM | Communications - Basic |
| CUI//LMI | Legislative Materials - Basic |
| CUI//LPROT | Protective Order - Basic |
| CUI//PHYS | Physical Security Information - Basic |
| CUI//PRIIG | Inspector General Protected Information - Basic |
| CUI//PRIVILEGE | Legal Privilege Information - Basic |
| CUI//PRVCY | General Privacy Information - Basic |
| CUI//SP-BUDG | Budget Information - Specified |
| CUI//SP-CRITAN | Ammonium Nitrate - Specified |
| CUI//SP-JURY | Federal Grand Jury Information - Specified |
| CUI//SP-PRVCY | General Privacy Information - Specified |
| CUI//XFER | Electronic Funds Transfer - Basic |
| CUP | Current Use Pesticide |
| CUSTODY | LEGAL CUSTODY; PHYSICAL CUSTODY |
| CUTOFF | FILE BREAK; FILE CUTOFF |
| CV | comparison value |
| CV Solution | Calibration Verification Solution |
| CVC | Citrus Variegated Chlorosis |
| CVD | Cardiovascular Disease |
| CVM | contingent valuation method |
| CVS | Cardiovascular System |
| CWA | Clean Water Act |
| CWA (Chemical) | Chemical Warfare Agent |
| CWA Hazardous Substance | Clean Water Act Hazardous Substance |
| CWD | Chronic Wasting Disease; coarse woody debris |
| CWLM | Cumulative Working Level Months |
| CWNS ID | Clean Watersheds Needs Survey ID |
| CWPB Process | Center-Worked Prebake Process |
| CWS | Community Water Systems |
| CWSRF Program | Clean Water State Revolving Fund Program |
| CWT Facility | Centralized Waste Treatment Facility |
| CyanoHAB | Cyanobacterial Harmful Algal Bloom |
| CYP | Cytochrome P450 |
| CYP 1A1 | Cytochrome P450 1A1 |
| CZMA | Coastal Zone Management Act |