United States Office of Water EPA 81 5-P-00-002 Environmental Protection Agency 4606 June 2001 Occurrence of Unregulated Contaminants in Public Water Systems-A National Summary r?% Printed on Recycled Paper ------- [This page left intentionally blank.] ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary TABLE OF CONTENTS TABLES AND FIGURES iii ACRONYMS v EXECUTIVE SUMMARY vii ACKNOWLEDGMENTS k DISCLAIMER x I. INTRODUCTION 1 I.A. Background 1 I.E. Unregulated and Regulated Contaminants, Databases, and Monitoring Timeframe 2 I.C. Data Analysis 7 II. DATA SOURCES AND DATA QUALITY REVIEW 8 II. A. URCIS (Round 1) Data 8 II. A. 1. Description of Data 8 II.A.2. Data Management and Data Quality 8 II.A.3. Further Data Review and Editing 9 II.B. SDWIS/FED (Round 2) Data 11 II.B.l. Description of Data 11 II.B.2. Data Management and Data Quality 11 II.B.3. Further Data Review and Editing 11 III. DEVELOPING A NATIONALLY REPRESENTATIVE PERSPECTIVE 13 III.A. Methods 14 III.A.1. Manufacturing Indicators 14 III.A.2. Agricultural Indicators 14 III.B. Representative Cross-Section of States 15 III.B.l. URCIS 24-State Cross-Section 15 III.B.2. Incremental National Cross-Sections 19 III.B.3. SDWIS/FED 20-State Cross-Section 19 IV DATA COVERAGE FOR THE NATIONAL OCCURRENCE OF CONTAMINANTS IN DRINKING WATER 22 IVA. URCIS (Round 1) Data Coverage 22 IVB. SDWIS/FED (Round 2) Data Coverage 23 IVC. Comparing Data Coverage of URCIS (Round 1) and SDWIS/FED (Round 2) 23 IV D. Comparing Data Coverage Across Systems Sizes and Types 24 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary V. ANALYSIS OF NATIONAL OCCURRENCE 24 V.A. URCIS (Round 1) Contaminant Occurrence 24 V.B. SDWIS/FED (Round 2) Contaminant Occurrence 27 VI. ASSESSMENTS OF SELECT HIGH OCCURRENCE CONTAMINANTS 30 VI. A. Select High Occurrence Contaminants and Detailed Graphical and Spatial Analysis . . 30 VLB. Graphical and Spatial Assessments of Select High Occurrence Contaminants 33 VI.B.l. Ethylene Dibromide 33 VLB.2. Tetrachloroethylene 34 VLB.3. Trichloroethylene 34 VI.B.4. Aldicarb Sulfoxide 34 VI.B.5. Dieldrin 35 VI.B.6. Metolachlor 35 VI.B.7. 1,1-Dichloroethane 35 VI.B.8. Chloromethane 35 VI.B.9. Chloroform 36 VLB. 10. Comparison of Occurrence in URCIS (Round 1) and SDWIS/FED (Round 2) 36 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary TABLES AND FIGURES Figure I.B.I. Diagram of the Inter-Relationship of Various Databases, Monitoring Rounds and Contaminant Lists Discussed in the Report ...................... 2 Table I.E. 1 . List and Description of Contaminants with Data in URCIS (Round 1) (approximately 1987-1992) ........................................... 3 Table I.B.2. List and Description of Contaminants with Data in SDWIS/FED (Round 2) (approximately 1993-1997) ........................................... 5 Table II.A.3.a. Summary of Data Quantity and Quality in URCIS (Round 1) for the States, Tribes, and Territories ............................................... 9 Table II.B.3.a. Summary of Data Quantity and Quality in SDWIS/FED (Round 2) for the States, Tribes, and Territories ........................................ 11 Table III.B. 1 . Ranking of States based on Number of Manufacturing Establishments per Square Mile. URCIS (Round 1) 24 State Cross-Section in Bold ............. 14 Figure III.B. 1 .a. Distribution of State Rankings for Manufacturing Establishments / Sq. Mile vs. Farm Ag. Chemical Expenses. Highlighting URCIS (Round 1) 24 Cross-Section States .................................... 16 Figure III.B. l.b. 24 URCIS (Round 1) Representative Cross-Section States and States Not Included in the Cross-Section ..................................... 17 Table III.B. 3. Ranking of States based on Number of Manufacturing Establishments per Square Mile. SDWIS/FED (Round 2) 20 Cross-Section States in Bold ........ 18 Figure III.B. 3. b. Distribution of State Rankings for Manufacturing Establishments / Sq. Mile vs. Farm Ag. Chemical Expenses. Highlighting SDWIS/FED (Round 2) 20 Cross-Section States .................................... 20 Figure III.B.3.b. 20 SDWIS/FED (Round 2) Cross-Section States and States Not Included in the Cross-Section ..................................... 21 Table V.A.I. URCIS (Round 1) 24-State Cross-Section Summary of Occurrence ............ 24 Table V.B. 1. SDWIS/FED (Round 2) Data - 20 State Cross-Section Summary of Occurrence ... 27 Table VI. A.I. Contaminant Occurrence Ranking of URCIS (Round 1) Data ................. 29 Table VI.A.2. Contaminant Occurrence Ranking of SDWIS/FED (Round 2) Data ............ 30 Table VI. A. 3. High Occurrence Contaminants Selected for Graphical and Spatial Assessments ... 31 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary [This page left intentionally blank.] IV ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary ACRONYMS Chemical Abstract Services (CAS) Chemical Monitoring Reform (CMR) Community Water System (CWS) Dibromochloropropane (DBCP) Environmental Protection Agency (EPA) Ethylene Dibromide (EDB) Ground Water (GW) Ground Water - Purchased (GWP) Ground Water Under Direct Influence (GUDI) Ground Water Under Direct Influence - Purchased (GUP) Health Advisory Level (HAL) Health Reference Level (HRL) Inorganic Chemical (IOC) Maximum Contaminant Level (MCL) Method Detection Limit (MDL) micrograms per liter (• g/L) milligrams per liter (mg/L) Minimum Reporting Level (or Limit, MRL) National Contaminant Occurrence Database (NCOD) National Primary Drinking Water Regulations (NPDWRs) National Water Quality Assessment Program (NAWQA) Non-Transient Non-Community Water System (NTNCWS) Office of Ground Water and Drinking Water (OGWDW) Percentage of Systems with Exceedances (>MCL/ >HRL/ >HAL) Percentage of Systems with Detections (>MRL) Public Water System (PWS) ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary ACRONYMS (continued) Public Water System Identifier (PWSID) Safe Drinking Water Act (SDWA) Safe Drinking Water Information System (SDWIS) Safe Drinking Water Information System/Federal Version (SDWIS/FED) Surface Water (SW) Surface Water - Purchased (SWP) Synthetic Organic Chemical (SOC) Tetrachloroethylene (PCE) Toxic Release Inventory (TRI) Transient Non-Community Water System (TNCWS) Trichloroethylene (TCE) Trihalomethane (THM) United States Geological Survey (USGS) Unregulated Contaminant Monitoring Information System (URCIS) Unregulated Contaminant Monitoring (UCM) Unregulated Contaminant Monitoring Regulation (UCMR) Volatile Organic Chemical (VOC) VI ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary EXECUTIVE SUMMARY This summary provides a condensed overview of the national occurrence report entitled Occurrence of Unregulated Contaminants in Public Water Systems: An Initial Assessment (EPA 815-P-00-001). The complete, original report, referred to as the "complete National Occurrence report," includes a comprehensive overview of the management and initial assessment of the unregulated contaminant occurrence data currently available to EPA. The data are from the required monitoring of unregulated contaminants conducted by public drinking water systems prior to 1998. Specifically, the assessments summarized here (and described in detail in the complete National Occurrence report referenced above) are based on the occurrence data from the Unregulated Contaminant Information System (URCIS) database and the Safe Drinking Water Information System/Federal Version (SDWIS/FED) database. The objective of the occurrence assessment is to enhance the scientific understanding of the occurrence of unregulated contaminants in public drinking water systems, and to refine the approach of management and analysis of contaminant occurrence data. The contaminant occurrence analyses and findings presented in this report are based on national cross-sections of state data (i.e., a subset of representative state data) derived from the URCIS (Round 1) and SDWIS/FED (Round 2) databases. The occurrence findings presented here are not based on the entire collection of state compliance monitoring data contained in the URCIS (Round 1) and SDWIS/FED (Round 2) databases. The data that were used as the basis for the analyses in this report are available upon request from EPA Office of Ground Water and Drinking Water. Requests for this data should be sent to ucmr.report(g),epa. gov. This summary report includes descriptions of Round 1 and Round 2 unregulated contaminant monitoring data, reviews the extensive data quality management necessary to conduct occurrence analyses, outlines the construction of a national cross-section of states from each of the two databases, and summarizes the occurrence analyses (based on the cross-sections) of the 62 unregulated contaminants in the Round 1 data set and the 48 unregulated contaminants in the Round 2 data set. The Round 1 data are contained in the URCIS database, and the Round 2 data are contained in the SDWIS/FED database. The URCIS database (Round 1 data) contains public water system monitoring results, generally from 1988 to 1992, for unregulated contaminants collected under the authority of the Safe Drinking Water Act (SDWA). Forty states/primacy entities have submitted PWS monitoring data to URCIS. Round 2 monitoring data, generally collected from 1993 to 1997, were reported directly to the SDWIS/FED database. Thirty-five states/primacy entities have submitted Round 2 PWS monitoring data to SDWIS/FED. The raw data from these two databases were reviewed extensively and edited for data quality considerations to ensure consistency and repeatability in the analyses. A data management approach was used in this study to develop a national cross-section of states that enables occurrence analyses that are indicative of national occurrence. All states with monitoring data were evaluated according to their distribution across a range of pollution potential indicators and spatial/hydrogeologic diversity. A select group of states, representing a balanced distribution across these pollution-potential measures and across the nation geographically, were then used to construct national cross-sections (one cross-section from Round 1 data, and another from Round 2 data) that would provide reasonable representation of national occurrence. While the national cross-sections cannot be considered "statistically representative," the constructed cross-sections are very large samples (24 and 20 states, respectively), providing analytical occurrence results that are clear indications of central tendency of the occurrence data, and are generally indicative of national contaminant occurrence. Vll ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary The cross-sections have been constructed with a large number of occurrence data to broadly reflect national coverage. The 24 cross-section states of URCIS (Round 1) data represent approximately 44% of public water systems nationally and 51% of the population served by public water systems. The 20 cross-section states of SDWIS/FED (Round 2) data represent approximately 41% of public water systems nationally and 34% of the population served by public water systems. The data from these two separate cross-sections are used to compute contaminant occurrence measures as an approximation of national occurrence. Summary assessments of data coverage and analyses of unregulated contaminant occurrence are then presented. Comparisons of Round 1 and Round 2 data coverage were made to evaluate if comparable states, public water systems, and contaminants are contained in both databases. Analytical summaries of occurrence of all contaminants for the Round 1 and Round 2 cross-section states are included. These occurrence assessments are based on measures such as the percent of public water systems with at least one analytical result greater than the minimum reporting level, and the percent of public water systems with at least one analytical result greater than the maximum contaminant limit (or heath reference level). This national summary concludes with a brief description of the more detailed spatial and graphical assessments of select high occurrence contaminants. The reader is referred to the complete National Occurrence report for full descriptions and more details of the data quality assessments, cross-section development, and contaminant occurrence analyses presented in this national summary. vm ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary ACKNOWLEDGMENTS The compilation and analysis of the data summarized in this report were undertaken by EPA's Office of Ground Water and Drinking Water (OGWDW) to enhance the scientific understanding of the occurrence of unregulated chemical contaminants in public drinking water systems, and to refine the approach of management and analysis of contaminant occurrence data. This effort was directed by Mr. Guy Caruthers of OGWDW. This project began under the direction of Mr. Charles Job. We would like to thank the many States, as well as the American Water Works Service Company, that contributed data sets and valuable advice. Thanks also to the many public water systems that conducted the monitoring that provided the contaminant occurrence data used in this report. Mr. Lewis Summers and Mr. Guy Caruthers of OGWDW managed the access to EPA's URCIS and SDWIS/FED databases, the repositories of data used in this project. The Cadmus Group, Inc. served as the prime contractor for this project, supporting the data management, analysis, and report development. Dr. George Hallberg and Dr. Jonathan Koplos served as Cadmus Project Managers. IX ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary DISCLAIMER This report does not constitute U.S. Environmental Protection Agency Policy. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This document is designed to provide technical background for the Office of Ground Water and Drinking Water's program. The document does not, however, substitute for the Safe Drinking Water Act or EPA's regulations nor is this document a regulation itself. Thus, it cannot impose legally-binding requirements on EPA, States, or the regulated community, and may not apply to a particular situation based on the circumstances. ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary I. INTRODUCTION This report provides a summary overview of the management and initial assessment of unregulated contaminant occurrence data currently available to EPA. The data are from the required compliance monitoring of unregulated contaminants conducted by public drinking water systems prior to 1998. Specifically, this report summarizes assessments based on occurrence data from the Unregulated Contaminant Information System (URCIS) database (Round 1 monitoring data) and the Safe Drinking Water Information System/Federal Version (SDWIS/FED) database (Round 2 monitoring data) that were comprehensively presented and described in the report entitled Occurrence of Unregulated Contaminants in Public Water Systems: An Initial Assessment (EPA 815-P-00-001; referred to as the "complete National Occurrence report"). The "complete National Occurrence report" includes a comprehensive overview of the assessment and initial analysis of the unregulated contaminant occurrence data currently available to EPA. This national summary, a condensed version of the complete National Occurrence report, presents a description of URCIS (Round 1) and SDWIS/FED (Round 2) data, reviews the extensive data quality management necessary to conduct occurrence analyses, outlines the construction of a national cross-section of states from each of the two databases, and summarizes the occurrence analytical findings for the 62 unregulated contaminants in the Round 1 data set and the 48 unregulated contaminants in the Round 2 data set. For complete, detailed evaluations and extensive tabulations of all contaminant occurrence findings for both Round 1 and Round 2 data, as well as spatial and graphical occurrence assessments of select high-occurrence contaminants, the reader is directed to the complete National Occurrence report referenced above (with the chapters in this national summary corresponding to the same in the complete National Occurrence report). I.A. Background The Safe Drinking Water Act (SDWA), as amended in 1986, required Public Water Systems (PWSs) to monitor for specified "unregulated" contaminants, on a five year cycle, and to report the monitoring results to the states. Unregulated contaminants do not have an established or proposed National Primary Drinking Water Regulation (NPDWR), but are formally listed and require monitoring under federal regulations. The intent is to gather scientific information on the occurrence of these contaminants to enable a decision regarding whether regulations were needed. All non-purchased community water systems (CWSs), and non-purchased non-transient non-community water systems (NTNCWSs), with greater than 150 service connections were required to conduct this unregulated contaminant monitoring. The 1993 amendments to SDWA added other contaminants to the unregulated contaminant list for required monitoring, and the 1996 SDWA amendments directed EPA to develop a revised program for such monitoring. This new program was formally published in the Federal Register on September 17, 1999 (64 FR 50556) as the Unregulated Contaminant Monitoring Regulation, now referred to as the UCMR (1999). This new UCMR monitoring will begin in 2001, and must produce a new list of unregulated contaminants for monitoring every 5-years. To clarify the history of unregulated contaminant monitoring, a naming system is introduced to distinguish between the different monitoring periods and the contaminant lists included in a specific monitoring period. The first unregulated contaminant monitoring list was published in 1987 and will be referred to as the UCM (1987) list. The UCM (1987) list was followed by the UCM (1993) list (generated through the 1993 SDWA Amendments) and the recent UCMR (1999) list (generated through the 1999 development of the Unregulated Contaminant Monitoring Regulation-UCMR-list of contaminants. The occurrence analyses in this report are based on the historic data from the UCM (1987) and UCM (1993) lists. Occurrence data for the UCM (1987) and UCM (1993) contaminants, as well as for other contaminants listed in the following section, are contained in two databases. (To date, ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary there are no data yet available from the UCMR monitoring, which was initiated in January, 2001.) These databases are briefly summarized in the following sections. I.E. Unregulated and Regulated Contaminants, Databases, and Monitoring Timeframe Figure I.B.I diagrams the inter-relationship of the various databases, monitoring rounds and contaminant lists discussed in this report. Tables I.B.I and I.B.2 describe in more detail the specific contaminants included in each database. Figure I.B.I. Diagram of the Inter-Relationship of Various Databases, Monitoring Rounds and Contaminant Lists Discussed in the Report URCIS (Round 1) (62 Contaminants) * refer to Table I.B.I for a complete list of contaminants UCM Phase I -21 VOCs 2 Regulated SOCs 5 Miscellaneous Contaminants 20 Mandatory VOCs (Group 3) 14 Discretionary VOCs (Group 4) SDWIS/FED (Round 2) (48 Contaminants) * refer to Table I.B.2 for a complete list of contaminants I— 13 SOCs (Group 1) UCM(1993)- 1 IOC (Group 2) UCM(1987) 20 Mandatory VOCs (Group 3) 14 Discretionary VOCs (Group 4) ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Table I.B.I. List and Description of Contaminants with Data in URCIS (Round 1) (approximately 1987-1992) Contaminant CAS Number SDWIS ID MCL HAL *, or HRL" uc Round UC Group Common Sources of Contaminant Inorganic Chemicals jNo Inorganic Chemicals in UCM (1987) data Sl nthetic Organic Chemicals - Regulated Dibromochloropropane ( 1 ,2-Dibromo-3 -chloropropane; or DBCP) Ethylene Dibromide (1,2-Dibromoethane; or EDB) 96-12-8 106-93-4 2931 2946 0.2 0.05 1 1 R R Soil fumigant on soybeans, cotton, pineapple, orchards Leaded gas additives; leaching of soil fumigant Volatile Organic Chemicals - Group 3 Bromobenzene Bromodichlorom ethane Bromoform Bromomethane (Methyl Bromide) Chloroform Chloroethane Chloromethane (Methyl Chloride) Dibromochloromethane Dibromom ethane 1 , 1 -Dichloroethane 1,3-Dichloropropane 2,2-Dichloropropane 1 , 1 -Dichloropropene 1,3-Dichloropropene m-Dichlorobenzene o-Chlorotoluene p-Chlorotoluene 1,1, 1 ,2-Tetrachloroethane 1,1,2,2-Tetrachloroethane 1,2,3-Trichloropropane 108-86-1 75-27-4 75-25-2 74-83-9 67-66-3 70-00-3 74-87-3 124-48-1 74-95-3 75-34-3 142-28-9 594-20-7 563-58-6 542-75-6 541-73-1 95-49-8 106-43-4 630-20-6 79-34-5 96-18-4 2993 2943 2942 2214 2941 2216 2210 2944 2408 2978 2412 2416 2410 2413 2967 2965 2966 2986 2988 2414 - 60** 400** 10 600** - 3 60** - 5 - - — 40** 600* 100 100 70* 2* 40 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Solvent, organic synthesis Disinfection-by-product, marine microalgae Disinfection-by-product, solvent for waxes, greases, oils Soil and space fumigant, extraction solvent, oceans Solvent, DBF, auto exhaust, chemical intermediate Chemical intermediate, solvent, aerosol, solvent metabolite Oceans, volcanoes, fires, smoke exhaust, solvent, DBF Organic synthesis, manufacture of fire extinguishing agents, refrigerants, aerosol propellants and pesticides. Solvent, gage fluid, use in chemical synthesis, marine algae Leaded gasoline; fumigants, paints Chemical intermediate for cyclopropane Solvent Solvent Solvent, used in fungicide Dump leachate, fumigant, solvent, chemical intermediate Drain pipe solvent Solvent, chemical intermediate for dyes, organic chemicals Product of manufacture of other chloroethanes Used in paint manufacturing; cement; paint removers; moth-proofing Paint/varnish remover, solvent, degreasing agent Volatile Organic Chemicals - Group 4 Bromochloromethane Dichlorodifluoromethane Hexachlorobutadiene 74-97-5 75-71-8 87-68-3 2430 2212 2246 10 1,000 0.9** 1 1 1 2 2 2 4 4 4 Organic synthesis and fire extinguishers Refrigerant, aerosol propellant, rocket propellant, foaming agent, plastics Solvent, synthetic rubber, pesticide, insecticide, herbi- cide, chemical intermediate ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Contaminant Isopropylbenzene n-Butylbenzene n-Propylbenzene Naphthalene p-Isopropyltoluene sec-Butylbenzene tert-Butylbenzene 1,2,3-Trichlorobenzene Trichlorofluorom ethane 1,2,4-Trimethylbenzene 1,3,5-Trimethylbenzene CAS Number 98-82-8 104-51-8 103-65-1 91-20-3 99-87-6 135-98-8 98-06-6 87-61-6 75-69-4 95-63-6 108-67-8 SDWIS ID 2994 2422 2998 2248 2030 2428 2426 2420 2218 2418 2424 MCL HAL *, or HRL" - - - 140** - — __ - 175* - — UC Round 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 UC Group 4 4 4 4 4 4 4 4 4 4 4 Common Sources of Contaminant Production of petroleum refining; evaporation and combustion of petroleum Solvent, used in textile dyeing and printing Fungicide, moth repellant Termite control; chemical intermediate Solvent, chemical intermediate, lialocarbon aerosol propellant and refrigerant Chemical intermediate, solvent, gasoline, coal tar, and petroleum products Volatile Organic Chemicals - Regulated Benzene Carbon tetrachloride Chlorobenzene cis- 1 ,2-Dichloroethylene 1,2-Dichloroethane Dichloroethene Dichloromethane (Methyl ene chloride) 1,2-Dichloropropane Ethyl benzene o-Dichlorobenzene p-Dichlorobenzene Styrene Tetrachloroethylene Toluene trans-l,2-Dichloroethylene 1 ,2, 4-Tri chlorobenzene 1,1,1 -Trichloroethane 1 , 1 ,2-Trichloroethane Trichloroethene (Trichloroethylene) Vinyl chloride 71-43-2 56-23-5 108-90-7 156-59-2 107-06-2 75-35-4 75-09-2 78-87-5 100-41-4 95-50-1 106-46-7 100-42-5 127-18-4 108-88-3 156-60-5 120-82-1 71-55-6 79-00-5 79-01-6 75-01-4 2990 2982 2989 2380 2980 2977 2964 2983 2992 2968 2969 2996 2987 2991 2979 2378 2981 2985 2984 2976 5 5 100 70 5 7 5 5 700 600 75 100 5 1,000 100 70 200 5 5 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 R R R R R R R R R R R R R R R R R R R R Some foods; gas, drugs, pesticide, paint, plastic industries Solvents and their degradation products Waste solvent from metal degreasing processes, discharge from chemical and agricultural chemical factories Waste industrial extraction solvents Leaded gas, fumigants, paints Plastics; dyes; perfumes; paints Paint stripper, metal degreaser, propellant, extraction Soil fumigant; waste industrial solvents Gasoline; insecticides; chemical manufacturing wastes Paints, engine cleaning compounds, dyes, chemical wastes Room and water deodorants, and "mothballs" Plastics, rubber, resin, drug industries; leachate from city landfills Improper disposal of dry cleaning and other solvents Gasoline additive; manufacturing and solvent operations Waste industrial extraction solvents Herbicide production; dye carrier Adhesives, aerosols, textiles, paints, inks, metal degreasers Solvent in rubber, other organic products; chemical production wastes Textiles, adhesives and metal degreasers May leach from PVC pipe; formed by solvent breakdown ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Contaminant Xylenes (Total) m-Xylene o-Xylene D-Xvlene CAS Number 1330-20-7 108-38-3 95-47-6 106-42-3 SDWIS ID 2955 2995 2997 2962 MCL HAL *, or HRL" 10,000 — — uc Round 1 1 1 1 2 UC Group R Common Sources of Contaminant By-product of gasoline refining; paints, inks, detergents Xylene Isomers Volatile Organic Chemicals - Other cis-l,3-Dichloropropylene trans- 1,3-Dichloropropylene 10061-01-5 10061-02-6 2228 2224 - - 1 1 Used in organic synthesis and soil fumigants; used as a nematocide Used in organic synthesis and soil fumigants for control of nematodes Includes some regulated SOCs and VOCs, and the unregulated contaminants from UCM (1987) List. UC Round = data included in Round 1 and/or 2 monitoring and database; UC Group = contaminant group as specified in UCM (1993) Listing. MCL=Maximum Contaminant Level HAL=Health Advisory Level (as of December 2000) HRL=Health Reference Level (concentration values used only as reference levels for analyses in this report) The MCL, HAL, and HRL values are used in this report only as reference levels to facilitate occurrence assessments. Table I.B.2. List and Description of Contaminants with Data in SDWIS/FED (Round 2) (approximately 1993-1997) Contaminant CAS Number SDWIS ID MCL HAL *, or HRL" (Hg/L) UC Round UC Group Common Sources of Contaminant Synthetic Organic Chemicals - Group 1 Aldicarb Aldicarb Sulfone Aldicarb Sulfoxide Aldrin Butachlor Carbaryl Dicamba Dieldrin 3 -Hydroxycarbofuran Methomyl Metolachlor Metribuzin Propachlor 116-06-3 1646-88-4 1646-87-3 309-00-2 23184-66-9 63-25-2 1918-00-9 60-57-1 16655-82-6 16752-77-5 51218-45-2 21087-64-9 1918-16-7 2047 2044 2043 2356 2076 2021 2440 2070 2066 2022 2045 2595 2077 7** 7** 7** 0.002** - 700 200 0.002** - 200 70** 91** 90 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 Pesticide used with cotton, potatoes, others (widely restricted) Biodegradation of aldicarb Biodegradation of aldicarb Soil insecticide Herbicide for rice, used on annual grasses Broad range pesticide (citrus, vegetables, lawns, nuts) Herbicide for agriculture, rangeland, pasture, industry Insecticide Metabolite of carbofuran Insecticide for soybeans, cotton, other field and fruit crops Herbicide for corn, soybeans, peanuts, cotton, pod crops Herbicide used on grass and broadleaf weeds Herbicide for corn and sorghum Inorganic Chemicals - Group 2 Sulfate 14808-79-8 1055 500,000** 2 2 Fertilizer, natural occurrence, some industrial uses ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Contaminant CAS Number SDWIS ID MCL HAL *, or HRL" (Hg/L) uc Round UC Group Common Sources of Contaminant Volatile Organic Chemicals - Group 3 Bromobenzene Bromodichlorom ethane Bromoform Bromomethane (Methyl Bromide) Chloroethane Chloroform Chloromethane (Methyl Chloride) Dibromochloromethane Dibromom ethane 1 , 1 -Dichloroethane 1,3-Dichloropropane 2,2-Dichloropropane 1 , 1 -Dichloropropene 1,3-Dichloropropene m-Dichlorobenzene o-Chlorotoluene p-Chlorotoluene 1,1, 1 ,2-Tetrachloroethane 1,1,2,2-Tetrachloroethane 1,2,3-Trichloropropane 108-86-1 75-27-4 75-25-2 74-83-9 70-00-3 67-66-3 74-87-3 124-48-1 74-95-3 75-34-3 142-28-9 594-20-7 563-58-6 542-75-6 541-73-1 95-49-8 106-43-4 630-20-6 79-34-5 96-18-4 2993 2943 2942 2214 2216 2941 2210 2944 2408 2978 2412 2416 2410 2413 2967 2965 2966 2986 2988 2414 - 60** 400** 10 - 600** 3 60** - 5 - — — 40** 600* 100 100 70* 2* 40 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Solvent, organic synthesis Disinfection-by-product, marine microalgae Disinfection-by-product, solvent for waxes, greases, oils Soil and space fumigant, extraction solvent, oceans Chemical intermediate, solvent, aerosol, solvent metabolite Solvent, DBF, auto exhaust, chemical intermediate Oceans, volcanoes, fires, smoke exhaust, solvent, DBF Solvent, gage fluid, use in chemical synthesis, marine algae Leaded gasoline; fumigants, paints Chemical intermediate for cyclopropane Solvent Solvent Solvent, used in fungicide Dump leachate, fumigant, solvent, chemical intermediate Drain pipe solvent Solvent, chemical intermediate for dyes, organic chemicals Product of manufacture of other chloroethanes Used in paint manufacturing; cement; paint removers; moth-proofing Paint/varnish remover, solvent, degreasing agent Volatile Organic Chemicals - Group 4 Bromochloromethane Dichlorodifluoromethane Hexachlorobutadiene Isopropylbenzene n-Butylbenzene n-Propylbenzene Naphthalene p-Isopropyltoluene sec-Butylbenzene tert-Butylbenzene 1,2,3-Trichlorobenzene 74-97-5 75-71-8 87-68-3 98-82-8 104-51-8 104-51-8 91-20-3 99-87-6 135-98-8 98-06-6 87-61-6 2430 2212 2246 2994 2422 2998 2248 2030 2428 2426 2420 10 1,000 0.9** - — - 140** — — — - 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 4 4 4 4 4 4 4 4 4 4 4 Organic synthesis and fire extinguishers Refrigerant, aerosol propellant, rocket propellant, foaming agent, plastics Solvent, synthetic rubber, pesticide, insecticide, herbi- cide, chemical intermediate Production of petroleum refining; evaporation and combustion of petroleum Solvent, used in textile dyeing and printing Fungicide, moth repellant Termite control; chemical intermediate ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Contaminant Trichlorofluorom ethane 1,2,4-Trimethylbenzene 1,3,5-Trimethylbenzene CAS Number 75-69-4 95-63-6 108-67-8 SDWIS ID 2218 2418 2424 MCL HAL *, or HRL" 175* - - UC Round 1 1 1 2 2 2 UC Group 4 4 4 Common Sources of Contaminant Solvent, chemical intermediate, halocarbon aerosol propellant and refrigerant Chemical intermediate, solvent, gasoline, coal tar, and petroleum products Includes the unregulated contaminants from UCM (1993) List. UC Round = data included in Round 1 and/or 2 monitoring and database; UC Group = contaminant group as specified in UCM (1993) Listing. MCL=Maximum Contaminant Level HAL=Health Advisory Level (as of December 2000) HRL=Health Reference Level (concentration values used only as reference levels for analyses in this report) The MCL, HAL, and HRL values are used in this report only as reference levels to facilitate occurrence assessments. I.C. Data Analysis The contaminant occurrence analyses and findings presented in this report are based on national cross-sections of state data (i.e., subsets of representative state data) derived from the URCIS (Round 1) and SDWIS/FED (Round 2) databases. The occurrence findings presented here are not based on the entire collection of state compliance monitoring data contained in the URCIS (Round 1) and SDWIS/FED (Round 2) databases. During initial URCIS and SDWIS/FED data quality assessments, significant data quality problems were identified. The data sources, data quality reviews, and the necessary data editing are described in detail in Section II of this report. Due to the data completeness and quality problems inherent in the raw URCIS and SDWIS/FED data, cross-sections of state data (one using URCIS data, and a second cross- section using SDWIS/FED data) were constructed to develop a nationally representative perspective for contaminant occurrence assessments. The detailed efforts to develop the nationally representative state cross-sections are described in Section III of this report. An overview of data coverage (distribution of system types, months, years, etc. of the occurrence data) of the two entire databases (and of the two cross-sections) is presented in Section IV. In Section V, the contaminant occurrence analytical findings are presented. Note that the findings are based on the constructed state cross-sections (not the entire URCIS and SDWIS/FED databases). The key summary findings are presented in Table V.A.1 (for the URCIS 24-state representative cross-section; see Appendix A for full detailed findings) and Table V.B.I (for the SDWIS/FED 20-state representative cross-section; see Appendix B for full detailed findings). Finally, Section VI presents additional occurrence assessments conducted for select high occurrence contaminants. The URCIS (Round 1) and SDWIS/FED (Round 2) data that were used as the basis for the analyses in this report are available upon request from EPA Office of Ground Water and Drinking Water. Requests for this data should be sent to ucmr.report(g),epa. gov. All statistical analyses, and most database manipulations were conducted with SAS® statistical software. Some data formatting problems were corrected in Microsoft® Excel with the aid of specialized programs written in Visual Basic® or were corrected directly in SAS before the analysis began. After ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary analysis, results were typically downloaded into Excel for secondary analysis, or sorting, or the development of report tables. II. DATA SOURCES AND DATA QUALITY REVIEW II.A. URCIS (Round 1) Data In this section of the summary, the unregulated contaminant monitoring data (from approximately 1988-1992) are reviewed for quantity, quality, and completeness. These Round 1 data were derived from the Unregulated Contaminant Information System (URCIS). Significant data review, formatting, and data quality checking and editing were required of this Round 1 data to enable the evaluations and analyses conducted for this initial contaminant occurrence assessment. II.A.1. Description of Data URCIS is a compilation of public water system monitoring results for unregulated contaminants, collected under the authority of SDWA, and reported to the states (as the primacy agents for SDWA). EPA requested that the states submit these data to EPA in the early 1990s, but no formal protocol or format had been established for reporting. Given the evolving nature of data management during this era, various data problems were encountered. EPA has been working on quality assurance and analysis of these data since 1992. Further data quality assessments and some preliminary analyses of the URCIS data were conducted and presented in the occurrence and data report prepared for EPA-OGWDW's Chemical Monitoring Revisions (CMR) project. This report,^ Review of Contaminant Occurrence in Public Water Systems (EPA 816-R-99-006, 1999, USEPA, Office of Water), is referred to as the "CMR Report". In 1999, EPA also transferred the URCIS data into SDWIS/FED, to join these URCIS Round 1 data with Round 2 data being submitted by the states into SDWIS/FED. (SDWIS/FED is the official database repository of data provided by public drinking water systems, and now includes data from an earlier EPA public water system URCIS database.) For the analyses described in this summary, the data from the original URCIS database was used. URCIS contained data from only 40 states/primacy entities. The URCIS database includes data on 62 Round 1 contaminants: the 34 UCM (1987) VOCs; the 21 regulated Phase 1 VOCs; 2 regulated synthetic organic contaminants (SOCs); and 5 miscellaneous contaminants. II.A.2. Data Management and Data Quality During the analytical work conducted for the CMR report in 1997-1998, the URCIS database was reviewed for various data quality problems and subsequently edited to remove readily apparent problematic data to ensure the quality of the data used in the analysis. Due to a variety of data quality problems, including incorrect or incomplete data codes for source water type, system type, system size (population-served), contaminant type, sample date, system identification, etc., some data records were excluded from the analyses to maintain defensible data quality. For some records, the data were of acceptable quality, but some system inventory information was missing. To enable use of these URCIS data records, the URCIS data were merged by public water system identification number (PWSID) with current SDWIS-Needs Survey PWS Inventory data to obtain missing system inventory information data on the source water, system type and population served for the ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary PWSs. After these data management and editing efforts, there are 3,452,530 analytical records for the 62 contaminants for analysis of the Round 1 data. Even with this extensive data management effort, there may still be data quality problems given the diverse sources of these data and the sheer size of the database. Recent reviews of the original database indicate that this does not appear to affect many data. II.A.3. Further Data Review and Editing Subsequent to the major editing efforts on this database, a secondary review of the 3.5 million records was undertaken. To begin, various descriptive statistics were compiled (state by state) to enable a more detailed review for data bias and representativeness. Some state data, as will be described, are so incomplete that their use would introduce bias into the analyses. These data are used in certain parts of this report to provide context or reference, but not to make determinations based on their occurrence analyses. Table II.A.3.a. summarizes results from the state data review. The table presents the data availability and data quality parameters assessed for 57 primacy entities considered under SDWA: the 50 states, 5 territories, the District of Columbia, and an aggregate entry for the Native American tribes. Contained in URCIS are data for 38 states, the Virgin Islands, and Washington, D.C. No data were reported for 17 primacy entities. An assessment of several parameters is used to determine if a state's data are complete (or adequately complete), or incomplete and biased. Indicators of biased data are high percent samples with detections (generally greater than 5 to 8 %), low number of samples per PWS (significantly below the common range of 50 to 250 samples per PWS), and low number of PWSs per state (as compared to the number of PWSs listed for a state in the SDWIS/FED inventory). The last column on Table II.A.3.a lists states with data records that are not complete (i.e., less than 100% of systems reported as compared to SDWIS/FED inventory listings), but have other parameters (e.g., "Percent Sample Detections", or "Samples per PWS") that suggest that the data are balanced and perhaps complete for the systems that did report. The last two columns, "States Usable for Cross-Section," identify the 27 primacy entities with adequate and unbiased data that were further considered for occurrence analyses. Table II.A.3.a. Summary of Data Quantity and Quality in URCIS (Round 1) for the States, Tribes, and Territories. States/ Tribes/ Territories 1 9 3 4 5 6 7 8 9 10 11 12 13 Alabama Alaska American Samoa Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Guam Hawaii Total Unique PWSs 152 748 - 973 6 4,167 60 - 13 855 1,165 - 127 Percent Sample detections 5% 2% 1% 100% 7% 34% 6% 20% 2% 1% Samples per PWS 136 132 151 5 111 38 1,207 14 120 370 No Data in Database American Samoa Connecticut Guam Data sets with 100% Detects Arkansas Significantly Too Few Systems Colorado Delaware States Usable for Cross- Section Most Complete Data sets Alaska Arizona California Georgia Hawaii Incomplete but Adequate Data sets Alabama Florida ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary States/ Tribes/ Territories 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Marianna Islands Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Puerto Rico Rhode Island South Carolina South Dakota Tennessee Texas Tribes Utah Vermont Virgin Islands Virginia Washington Washington, D.C. West Virginia Wisconsin Wyoming TOT4L Total Unique PWSs - 1,307 415 1,002 - 525 13 - - 998 220 139 1,565 206 85 565 214 10 201 1,551 617 357 298 - 2,657 - - - - - - 335 306 124 - 430 133 3 - 992 1 139 - 145 23,819 Percent Sample detections 5% 4% 5% 3% 3% 2% 91% 100% 1% 100% 1% 2% 100% 2% 100% 2% 0% 1% 2% 1% 4% 4% 98% 1% 82% 9% 1% 5% 6% 3% 2.9% Samples per PWS 147 292 62 273 95 105 14 16 100 6 215 94 6 860 5 94 151 348 134 313 52 197 2 150 10 186 229 3,432 157 125 146 No Data in Database Idaho Kansas Maine Marianna Islands North Dakota Oklahoma Oregon Pennsylvania Puerto Rico Rhode Island South Carolina Tribes Virginia Wisconsin 17 Data sets with 100% Detects Vlassachusetts Michigan Mississippi Nebraska New Texas Vermont 8 Significantly Too Few Systems Louisiana Missouri Nevada 5 States Usable for Cross- Section Most Complete Data sets Illinois Indiana Iowa Kentucky Maryland Minnesota Montana New Jersey New Mexico Ohio South Dakota Tennessee Utah Washington Washington, Wyoming 21 Incomplete but Adequate Data sets New York North Virgin West 6 10 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary II.B. SDWIS/FED (Round 2) Data The monitoring data for the UCM (1993) list of unregulated contaminants (from Round 2, approximately 1992-1997) are reviewed in this section of the summary. These Round 2 data were derived from the Safe Drinking Water Information System/Federal Version (SDWIS/FED). Significant data review, formatting, and data quality checking and editing were required of this Round 2 data to enable the evaluations and analyses conducted for this contaminant occurrence assessment. II.B.1. Description of Data Data for this portion of the analysis were downloaded from the SDWIS/FED database. The unregulated data include records from the second round of unregulated contaminant monitoring (referred to as "Round 2") that were submitted directly into SDWIS/FED. These data were generated through monitoring conducted during Round 2 of required unregulated contaminant monitoring initiated in 1993. (Although second round monitoring was formally initiated in 1993, SDWIS/FED (Round 2) data can include older data that are comparable to, but predate, the formal second round monitoring.) SDWIS/FED contained Round 2 data from 35 states/primacy entities. The SDWIS/FED (Round 2) data includes information on 48 contaminants, including: 1 IOC, 13 SOCs, 20 mandatory VOCs, and 14 discretionary VOCs. II.B.2. Data Management and Data Quality The SDWIS/FED Round 2 data comprise 4,350,874 raw records. An important and substantial component of this study consisted of the detailed and extensive review of these data records for numerous data quality considerations including reporting consistencies, uniform and valid coding, data completeness, correct and consistent use of analytical units, and any inherent bias in the raw records. Common types of data problems that were addressed include records with invalid contaminant codes, systems with unknown source water or system type codes, state records for specific contaminants that reported only detections, or entire state records that appeared to have extremely and consistently low analytical results. These types of records were either deleted (such as when water source or system type codes were invalid) or converted (when a data units conversion appeared straightforward). Another more general data management decision related to data from transient and "non-public" water systems. To avoid the problems associated with transient sources in exposure studies, systems with a system type recorded as "NC" (non-community, meaning transient) were not included in the occurrence analyses. With these data management and quality improvements, the initial 4,350,874 analytical records decreased to 4,211,446 analytical records (which includes approximately 900,000 records with converted units). II.B.3. Further Data Review and Editing Subsequent to the initial editing and filtering of the data described above, a basic analysis of the 4.21 million records was undertaken. Similar to the URCIS (Round 1) data, various descriptive statistics were compiled, by state, to enable a further, more detailed data review to assess data bias and representativeness. Some state data, as will be described, are so incomplete that their use would introduce bias into the analyses. These data are used in certain parts of this report to provide context or reference, but not to make determinations based on their occurrence analyses. ll ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Table II.B.S.a summarizes some key results from the Round 2 state data review. The table presents the data availability and data quality parameters assessed for the 57 primacy entities considered under SDWA. Of the 57 primacy entities in SDWIS/FED, 35 have reported Round 2 data and 22 have not. An assessment of several parameters is used to determine if a state's data are complete (or adequately complete), or incomplete and biased. Indicators of biased data are high percent samples with detections (generally greater than 5 to 8%), low number of samples per PWS (significantly below the common range of 50 to 250 samples per PWS), and low number of PWSs per state (as compared to the number of PWSs listed for a state in the SDWIS/FED inventory). The last column on Table II.B.S.a, "States Usable for Cross-Section," lists states with data records that are reasonably balanced and perhaps complete for the systems that did report. These 20 Round 2 primacy entities with adequate and unbiased data were further considered for occurrence analyses. Table II.B.3.a. Summary of Data Quantity and Quality in SDWIS/FED (Round 2) for the States, Tribes, and Territories. State/ Tribes/ Territories 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Alabama Alaska American Samoa Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Guam Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine \larianna Islands Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Mevada Mew Hampshire Mew Jersey Mew Mexico Total Unique PWSs 314 625 - 123 577 67 833 87 - - - - - - - 120 - - 445 1,394 745 - 1,015 506 3,209 1,581 1,155 1,434 - - - 849 17 755 Percent Sample Detections 94.08% 3.10% 2.75% 7.29% 6.75% 3.72% 4.53% 2.26% 7.50% 0.00% 0.89% 0.62% 3.12% 7.26% 1.66% 71.27% 6.08% 5.45% 2.32% 0.75% Samples per PWS 2 194 55 118 44 143 921 58 125 118 163 140 125 97 198 4 109 23 28 277 No Data in Database American Samoa Delaware Florida Georgia Guam Hawaii Idaho Illinois Iowa Kansas Marianna Islands Montana Nebraska Nevada Data sets with 100% Detects Alabama Mississippi Significantly Too Few Systems Arizona California Connecticut Indiana New Jersey )ata Quality Problems Louisiana States Usable for Cross- Section Alaska Arkansas Colorado Kentucky Maine Maryland Massachusetts Michigan Minnesota Missouri New New Mexico 12 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary State/ Tribes/ Territories 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Mew York Morth Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Puerto Rico Rhode Island South Carolina South Dakota Tennessee Texas Tribes Utah Vermont Virgin Islands Virginia Washington Washington, D.C. West Virginia Wisconsin Wyoming TOT4L Total Unique PWSs - 2,263 296 2,259 888 1,168 1,424 - 117 1,047 27 78 4,863 26 - 636 - - 2,680 - - 225 - 33,848 Percent Sample Detections 2.05% 7.73% 3.45% 3.99% 1.66% 10.19% 0.30% 0.33% 2.34% 9.31% 1.23% 1.22% 2.65% 2.23% 1.41% 2.95% Samples per PWS 55 59 291 180 75 16 136 147 40 147 124 57 74 123 51 124 No Data in Database New York Puerto Rico Utah Virgin Islands Virginia Washington, D.C. West Virginia Wyoming 22 Data sets with 100% Detects 2 Significantly Too Few Systems South Dakota Tennessee Tribes Wisconsin 9 )ata Quality Problems Pennsylvania South Carolina Vermont 4 States Usable for Cross- Section North North Dakota Ohio Oklahoma Oregon Rhode Island Texas Washington 20 III. DEVELOPING A NATIONALLY REPRESENTATIVE PERSPECTIVE The data quality evaluation suggested that Round 1 data from 25 states (plus Washington, D.C. and the Virgin Islands, totaling 27 primacy entities) were most complete and might be used to generate national summary statistics on occurrence of the contaminants in URCIS. Data from 25 of the 50 states is a substantial sample. However, even a 50 percent sample does not guarantee that the sample is representative because the data were not collected in a systematic or random statistical framework. Therefore, the state data were evaluated to assess how representative they were across the range, from high to low, of likely contaminant occurrence and across the spatial/hydrologic diversity of the nation. Based on these assessments, the construction of a cross-section of states from the available state data sets provides a reasonable representation of national occurrence. There are many sophisticated statistical methods that can be applied to analyze limited (and biased) data. This development of a representative cross-section of data is undertaken to support this initial occurrence analysis. The representative cross-section can also serve as the basis for subsequent, more sophisticated analyses as deemed necessary and appropriate by the initial occurrence assessments conducted in this report. For this initial analysis, the approach used was developed for the CMR report, A Review of Contaminant Occurrence in Public Water Systems (EPA 816-R-99-006, 1999), to establish a national cross-section from state SDWA contaminant databases. This approach was supported by peer reviewers and by stakeholders as providing a clear, repeatable, and understandable approach. It cannot provide a "statistically representative" sample, because the data were not selected in an appropriate fashion. The resultant data should, however, provide a clear indication of the central tendency of the national data. 13 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary III.A. Methods For the CMR Report (referenced above), a protocol was developed for determining a representative cross-section of states for occurrence analysis. In the CMR analysis, contaminant data were available directly from 14 states. The state data were evaluated for completeness and quality (similar to the data quality evaluations in this report). The balance of the states with adequately complete and high quality data were evaluated to establish a national cross-section. In the CMR process, eight states were selected for use in a national analysis as providing the best data quality and completeness, and for providing a balanced national cross-section of occurrence data. The CMR process was based on evaluating the states' pollution potential and geographic coverage in relation to all states. The URCIS and SDWIS/FED states were evaluated using the same selection process. Two broad factors were considered in the assessment of a representative cross-section: pollution potential and geographic or spatial diversity. Pollution potential is considered to ensure that the selection of cross-section states represents the range of likely high, medium, and low contaminant occurrence. Geographic consideration is included so that the wide range of climatic and hydrogeologic conditions across the United States are represented, again balancing the varied conditions that affect transport and fate of contaminants. For this analysis, two primary pollution potential indicators were used to evaluate the representativeness of the states. One factor indicates the pollution potential from manufacturing (generally related to VOC occurrence) and the second factor refers to pollution potential from agriculture (generally related to SOC occurrence). States were ranked from 1 to 50 for each factor and divided into quartiles based on the ranking. The rankings were reviewed to assess if states could be selected in approximate balance from each quartile. III.A.1. Manufacturing Indicators Numerous factors were considered in the CMR analysis as potential indicators of manufacturing- related pollution, including EPA's Toxic Release Inventory (TRI), the number of manufacturing establishments, the number of manufacturing establishments per square mile, the number of manufacturing employees, the product value added by manufacturers, and the value added per capita. These factors were each considered in terms of their inherent value as pollution potential indicators, their range and variance (in providing a relative ranking of the states), their inter-relationships, and consistency in data collection. Based on these considerations, the number of manufacturing establishments per square mile was used as the primary indicator for potential VOC pollution. III.A.2. Agricultural Indicators There is no complete measure of pesticide usage by states which is readily available. Therefore, a variety of factors were considered to assess potential synthetic organic chemical pollution from agriculture in each state. These included the percent of the state's population that is classified as rural, the percent of land in the state that is crop land, the percent of land that is grassland pasture and rangeland (a possible inverse indicator), and total farm agricultural chemical expenses. Like the manufacturing factors, these agricultural variables were considered in terms of their value in indicating potential sources of pollution and were plotted against one another to determine how closely they are related. Of these factors, total farm agricultural chemical expenses was considered to be the most direct indicator of potential pollution for SOCs. 14 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary III.B. Representative Cross-Section of States Using the method and indicators described above, state cross-sections are developed from the states with unbiased, complete, and relatively good quality data in URCIS and SDWIS/FED. The cross- section states were selected to provide a relatively balanced distribution of pollution potential and geography, so that the cross-sections approximate a representative national distribution. III.B.l. URCIS 24-State Cross-Section Table III.B.l summarizes the state pollution potential rankings, highlighting those included in URCIS. Although data from 38 states (and Washington D.C. and Virgin Islands), are included in URCIS, not all states were usable in a "representative" cross-section (as discussed in Section II). Thirteen states contained only detections or too few analytical records, or records from too few PWSs and were eliminated from consideration because of their inherent bias. The data from Washington, D.C. and Virgin Islands were excluded from this state-level analysis because it was difficult to evaluate them in relation to complete state data. The data quality screening left 25 states eligible for the national cross-section. New York was excluded because of inherent data quality problems, leaving 24 states. Table III.B.l. Ranking of States based on Number of Manufacturing Establishments per Square Mile. URCIS (Round 1) 24 State Cross-Section in Bold. State Ihode Island Vew Jersey Connecticut Vlassachusetts 4ew York Ohio Maryland "ennsylvania Delaware llinois California i1 orida Michigan 4ew Hampshire ndiana Vorth Carolina Wisconsin Tennessee Georgia Virginia South Carolina lawaii Vermont Washington Alabama Vlissouri Kentucky Minnesota jOuisiana Texas Mississippi Arkansas Ranking of the Number of Manufacturing Establishments/ Sq. Mile 1 2 3 4 5 6 7 8 9 10 11 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Ranking of the Total Farm Ag. Chemical Expenses 49 37 45 43 28 11 35 29 39 2 1 4 18 48 7 17 20 24 19 30 32 36 47 14 26 12 27 5 13 6 8 10 15 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary State West Vireinia Oregon Vlaine [owa Oklahoma Colorado Kansas Arizona Utah Nebraska Idaho New Mexico South Dakota Mevada North Dakota Montana Wyoming 41aska Ranking of the Number of Manufacturing Establishments/ Sq. Mile 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 l=highest Ranking of the Total Farm Ag. Chemical Expenses 44 22 38 3 33 31 16 25 42 9 23 40 21 46 15 34 41 50 l=highest All 50 states are ranked based on the number of manufacturing establishments per square mile. Each state's rank in total farm agricultural chemical expenses is also indicated. The 38 states in shaded rows are the states with data in the URCIS (Round 1) database. The 24 states in bold are the selected URCIS (Round 1) cross-section states. Ranking quartiles are indicated by bold lines. Figure III.B.l.a. summarizes the representativeness of the pollution potential distribution across the ranking quartiles of the 24 cross-section states. Figure III.B.l.b. shows the geographic distribution of these 24 cross-section states (and of the 26 excluded states). The consideration of a broad and diverse geographic representation of states serves to address and include the potential range of naturally occurring contaminants as represented by the inorganic chemicals, lOCs. As illustrated, the 24 states are quite well distributed based on pollution potential indicators, with a uniform distribution from high to low potential for both key pollution indicators (Figure III.B.l.a.). While geographic coverage is lacking from the south-central U.S. and New England, the 24 cross-section states provide broad coverage from around the country, from the major climatic regions, and include about 49% of the PWSs nationally and about 56% of population served by PWSs. 16 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Figure IILB.l.a. Distribution of State Rankings for Manufacturing Establishments / Sq. Mile vs. Farm Ag. Chemical Expenses. Highlighting URCIS (Round 1) 24 Cross-Section States ing uf LIic NU. of Miiiiuf«iL.:l.iiiiiiy FiMjiljMiti CHIN' Sq. Mile TOW TO TTTCiTT i o 0 e * D * • ' . O 0* o o Q ° c D a o K - * 0 * 0 i o o * 0 0 ft • o ° * o o o TTIV«7T TO -LOW 53 a. (£ • LRC1S (Round 1) 24-Stile O 3i S luc-i :v OT ill LRCi S ( K.O mid 1) Cross- Sculk 17 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Figure IILB.l.b. 24 URCIS (Round 1) Representative Cross-Section States and States Not Included in the Cross-Section URCIS (Round 1) URCIS (Round 1) States I I States not in Cross-Section (no data) I I States with biased data I I 24 Cross-Section States (data used in report) In sum, the group of 24 cross-section states in URCIS (Round 1), should provide a balanced representation, based on relative rankings for pollution potential (i.e., potential for contaminant occurrence), geographic coverage, and data quality and completeness. The 24 cross-section state distribution across pollution potential quartiles suggests that they should provide a valid indication of the potential range and occurrence of contamination in public water systems nationally. The data from the 24-state cross-section are used to compute aggregate contaminant occurrence measures as an approximation of a national cross-section. While the data from these cross-section states cannot be stated to be "statistically representative," their distribution should provide a representative view and clear indication of national central tendency of occurrence. In addition, the URCIS data, with 24 states in its cross-section, represent a relatively large collection of state data for a cross-section. As noted, the CMR analysis developed a cross-section of 8 states. The data from the URCIS 24 cross-section states can also be used to evaluate and illustrate this approach to constructing a national cross section by evaluating the data in aggregate steps, using increments of the 24 states. This approach is described below. 18 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary III.B.2. Incremental National Cross-Sections The data from the 24 URCIS cross-section states were used to build "incremental" national cross-sections, by aggregating subsets of the 24 states using the same selection protocol for evaluating representativeness. Each aggregate (e.g., 4 states, 8 states, etc.) provides some representation of all quartiles of pollution potential indicators, a geographic balance, and, hence, hopefully, a balance in potential occurrence. The data from the states in each aggregate were used to compute group contaminant occurrence measures (such as percent systems with at least one analytical detection of a particular contaminant). The results from the 4-state, 8-state, and 13-state cross-section (data aggregations) were then compared to the same measures based on the 24-state cross-section. The 8-state through the 24-state cross-sections provide comparable results. This consistency of analytical results across the different number of state cross-section groups suggests that the criteria used to construct the aggregations are valid. Again, while the data from these cross-section states cannot be stated to be "statistically representative," their distribution should provide a clear indication of national central tendency of occurrence. The results using the 24-state cross-section will be further described in later sections of this report. The validity and value of the national cross-section sample could be further tested if necessary. III.B.3. SDWIS/FED 20-State Cross-Section Table III.B.3. summarizes the pollution potential rankings for the 50 states, highlighting (in bold) those included in SDWIS/FED. Although a total of 34 state data sets are included in SDWIS/FED Round 2 data, not all states were usable in constructing a "representative" cross-section (as discussed in Section II). The data quality screening left 20 states eligible for the national cross-section. In Figure III.B.3.a, the distribution of the pollution potential rankings of the 20 cross-section states illustrates how representative the cross-section states are as based on these characteristics. Table III.B.3. Ranking of States based on Number of Manufacturing Establishments per Square Mile. SDWIS/FED (Round 2) 20 Cross-Section States in Bold. State Rhode Island New Jersey Connecticut Massachusetts New York Ohio Maryland Pennsylvania Delaware Illinois California Florida Michigan New Hampshire Indiana North Carolina Wisconsin Tennessee Georgia Ranking of the Number of Manufacturing Establishments/ Sq. Mile 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Ranking of the Total Farm Ag. Chemical Expenses 49 37 45 43 28 11 35 29 39 2 1 4 18 48 7 17 20 24 19 19 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary State Virginia South Carolina Hawaii Vermont Washington Alabama Missouri Kentucky Minnesota Louisiana Texas Mississippi Arkansas West Virginia Oregon Maine Iowa Oklahoma Colorado Kansas Arizona Utah Nebraska Idaho New Mexico South Dakota Nevada North Dakota Montana Wyoming Alaska Ranking of the Number of Manufacturing Establishments/ Sq. Mile 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 l=hiehest Ranking of the Total Farm Ag. Chemical Expenses 30 32 36 47 14 26 12 27 5 13 6 8 10 44 22 38 3 33 31 16 25 42 9 23 40 21 46 15 34 41 50 l=hiehest All 50 states are ranked based on the number of manufacturing establishments per square mile. Each state's rank in total farm agricultural chemical expenses is also indicated. The 34 states in shaded rows are the states with data in the SDWIS/FED database. The 20 states in bold are the selected SDWIS/FED (Round 2) cross-section states. Ranking quartiles are indicated by bold lines. 20 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Figure III.B.3.b. Distribution of State Rankings for Manufacturing Establishments / Sq. Mile vs. Farm Ag. Chemical Expenses. Highlighting SDWIS/FED (Round 2) 20 Cross-Section States Riiliking i.if LIic NU. of Miiiiuf«iL.:l.iiiiiiy FiMjiljMiti cnLiS'' Sq. Mile IfiW TO VI. - KILP- TTTCiTT o * e o D O O 0 * 0 o • o o Q * * * O o * K o •^ o o o O Q °o "> . _ o ° o o * TO -LOW f£ "•3 • SU VVI &''! TD (Round 2> 2'J- Sutc C O 3D State-, NOT ill SlJWlS.-T'liD Ctonnd 2j Crow Section 21 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary The geographic distribution of the 20 SDWIS/FED Round 2 cross-section states is presented in Figure III.B.S.b. Geographically, the 20 Round 2 cross-section states are widely distributed across the country. Although coverage is perhaps sparse in the south-east and along the western slope of the Rocky Mountains, every major geographic region has some state representation. Figure III.B.3.b. 20 SDWIS/FED (Round 2) Cross-Section States and States Not Included in the Cross-Section SDWIS/FED (Round 2) SDWIS/FED (Round 2) States I I States not in Cross-Section (no data) I I States with biased data 20 Cross-Section States (data used in report) IV. DATA COVERAGE FOR THE NATIONAL OCCURRENCE OF CONTAMINANTS IN DRINKING WATER IV.A. URCIS (Round 1) Data Coverage A descriptive overview of the Round 1 data is presented to provide additional insight and perspective on the results. After data management and editing, 3.45 million records were available for analysis representing over 24,000 PWSs from the 40 states/entities. For the 24 states comprising the URCIS representative cross-section (see Section III for a discussion regarding the cross-section), the analytical results total is 3.27 million records, from 22,034 PWSs. Of the approximately 22,000 systems with data represented in the cross-section states, about 88% are classified as ground water and 12% as using surface water. Approximately 65% of the cross-section systems are categorized as Community Water Systems (CWSs ), 22% Non-Transient Non-Community 22 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Water Systems (NTNCWS), about 8% Non-Community Water Systems (NCWS), and 5% with unknown system type designations. The majority of data were collected during the 1987-1992 compliance cycle, with a peak of data collection in 1991. Although in the month of March there is a slightly greater percentage of data, there is no significant difference in the number of records from month to month, suggesting that there should be no seasonal bias due to monthly differences in reporting. IV.B. SDWIS/FED (Round 2) Data Coverage After initial data management and editing, 4.21 million records were available for analysis from over 33,000 PWSs in the 35 states/entities. The 20 SDWIS/FED Round 2 state cross-section totals 3.69 million records from slightly more than 27,000 PWSs. The Round 2 cross-section states, therefore, contain nearly 88% of all Round 2 state contaminant occurrence data in SDWIS/FED. Of the approximately 27,000 systems with data represented in the Round 2 cross-section states, about 89% are classified as ground water and 11% as using surface water. These source water percentages are essentially the same for the entire Round 2 data set for all 35 states/entities. Approximately 70% of the cross-section systems are categorized as Community Water Systems (CWSs ), and 30% as Non-Transient Non-Community Water Systems (NTNCWS). This proportional distribution of system types is very similar to that for all the Round 2 data. The majority of data were collected during 1992-1997, with a peak of data collection in 1995. Although there is a very slightly greater percentage of data in March, a fairly uniform distribution of occurrence data by month suggests that there should be no inherent seasonal bias in the data. IV.C. Comparing Data Coverage of URCIS (Round 1) and SDWIS/FED (Round 2) The URCIS (Round 1) and SDWIS/FED (Round 2) data were evaluated to determine if comparable states, public water systems (PWSs), and contaminants are contained in both databases. As previously noted, URCIS contained data from 40 states/territories, and SDWIS/FED data consisted of analytical results from 35 states/territories. Of the 25 states with data in both URCIS (Round 1) and SDWIS/FED (Round 2), only 8 were determined to be sufficiently complete for use in this comparison analysis. Alaska, Kentucky, Maryland, Minnesota, North Carolina, New Mexico, Ohio, and Washington were contained in both databases and have data of adequate quality for analyses and comparisons. In addition, a determination was made regarding actual PWSs that are common to both databases. Thirty-one percent of all PWSs in URCIS (Round 1) are also in SDWIS/FED (Round 2), while only 22% of all SDWIS/FED (Round 2) PWSs are common to both rounds. This is, in part, because there are many more systems reporting analytical results in SDWIS/FED (Round 2) than in URCIS (Round 1). Comparisons of contaminants in URCIS (Round 1) and SDWIS/FED (Round 2) indicated that there were no common lOCs (Group 1) or SOCs (Regulated or Group 2) reported in both databases. In contrast, all of the unregulated Group 3 and Group 4 VOCs reported in SDWIS/FED (Round 2) were also reported in URCIS (Round 1). None of the regulated VOCs reported in URCIS (Round 1), however, were reported in SDWIS/FED (Round 2). 23 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Changes in the percentages of samples and percentage of PWSs with at least one analytical result greater than the MRL followed no consistent pattern either for the contaminants or states with data in both rounds. The percentage of PWSs with at least one analytical result exceeding the concentration of the MCL/HRL (or 1A MCL/HRL) also followed no apparent or consist pattern between URCIS (Round 1) and SDWIS/FED (Round 2). IV.D. Comparing Data Coverage Across Systems Sizes and Types Data for select contaminants were also evaluated based on system type and size. Both the URCIS (Round 1) and SDWIS/FED (Round 2) data were reviewed according to system size (with the data stratified and assessed according to the five standard population-served categories) and according to type (comparing community water systems and non-transient non-community water systems). Generally, for both Round 1 and 2 data, the percentage of public water systems with analytical results greater than the MRL and the MCL/HRL increases as the system size (population-served) increases. Also, it appears to generally be the case that the percentage of public water systems with analytical results greater than the MRL and the MCL/HRL is greater for community water systems than for non-transient non-community water systems. Note that there is a much greater number of CWSs than NTNCWSs in the databases. V. ANALYSIS OF NATIONAL OCCURRENCE In this section, general summaries of contaminant occurrence data from URCIS (Round 1) and SDWIS/FED (Round 2) are presented. The summary data developed for the occurrence assessments in this report are presented in detail in Appendices A, B, C, and D in the complete National Occurrence report. Appendix A contains summary tables for the 62 URCIS (Round 1) contaminant data. Appendix B contains summary tables for the 48 SDWIS/FED (Round 2) contaminant data. In Appendix C, data coverage comparisons between URCIS (Round 1) and SDWIS/FED (Round 2) data are presented for select states and contaminants. Data summaries of select contaminants by system type and population- served for both URCIS (Round 1) and SDWIS/FED (Round 2) data are presented in Appendix D of the complete National Occurrence report. A brief review of these findings is included the following sections of this national summary. V.A. URCIS (Round 1) Contaminant Occurrence Table V.A.1 summarizes the occurrence data of the URCIS (Round 1) 24 state cross-section for 62 contaminants. The table presents the total number of unique public water systems, the percent of public water systems with at least one monitoring sample analytical result greater than the MRL, the percent of public water systems with at least one result greater than the estimated MCL/HRL/HAL and, finally, the 99th percentile value in micrograms per liter (• g/L). (To review a map of the URCIS Round 1 cross-section states, refer to Figure III.B.l.b.) The 24 URCIS cross-section states reflect significant national coverage: these states contain approximately 44% of public water systems nationally and 51% of the population served by public water systems. For the majority of contaminants evaluated here (35 out of 62), less than 1% of public water systems in the cross-section states have analytical detections (any sample analytical result greater than the MRL). Another 16 contaminants are detected in 1 to 2% of public water systems, as evidenced by one or more sample analytical results greater than the MRL. Seven contaminants 24 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary (Dibromochloropropane, Dichloromethane, Tetrachloroethylene, Toluene, 1,1,1-Trichloroethane, Trichloroethylene, and total Xylenes) are detected in 2 to 4% of public water systems, as evidenced by one or more sample analytical results greater than the MRL. The four THMs have a considerably higher percent of systems (ranging from 9.01% to 28.84%) with at least one sample analytical result greater than the MRL. Select URCIS (Round 1) high occurrence contaminants are identified and assessed in Section VI. Table V.A.I. URCIS (Round 1) 24-State Cross-Section Summary of Occurrence CHEMICAL NAME (Threshold in ug/L) Total # PWS #GW PWS #SW PWS % PWS >MRL % GW PWS >MRL % sw PWS >MRL % PWS > Threshold % GW PWS> Threshold % SW PWS> Threshold 99% Value (MS/L) SOCs Dibrom ochloropropane (MCL=0.2) Ethylene Dibrom ide (MCL=0.05) 12,827 11,450 11,446 10,274 1,511 1,284 2.49% 1.14% 2.51% 1.01% 2 32% 2.10% 1.32% 0.16% 1.35% 0.12% 0.99% 0.47% 1.03 0.01 VOCs Benzene (MCL=5) Bromobenzene (N/A) Bromochlorom ethane (MCL=10) Bromodichlorom ethane (HRL=60) Bromoform (HRL=400) Bromom ethane (MCL=10) Carbon Tetrachloride (MCL=5) Chlorobenzene (MCL=100) Chloroethane (N/A) Chloroform (HRL=600) Chlorom ethane (MCL=3) cis-l,2-Dichloroethene (MCL=70) cis-l,2-Dichloropropene (N/A) Dibromochlorom ethane (HRL=60) Dibrom om ethane (N/A) Dichlorodifluorom ethane (MCL=1,000) 1 , 1 -Dichloroe thane (MCL=5) 1 ,2-Dichloroe thane (MCL=5) Dichloroethene (MCL=7) Dichloromethane (MCL=5) 1 ,2-Dichloropropane (MCL=5) 14,910 16,450 12,881 20,024 19,582 20,198 15,266 20,038 20,236 20,039 20,246 16,705 9,211 19,750 16,549 16,076 20,483 15,282 15,430 19,287 19,591 13,919 14,862 11,576 17,917 17,773 18,472 14,176 18,337 18,507 17,874 18,513 15,026 8,438 17,785 14,953 14,617 18,758 14,192 14,180 17,602 17,908 1,119 1,726 1,386 2,324 1,979 1,886 1,214 1,859 1,882 2,385 1,894 1,832 836 2,158 1,720 1,588 1,876 1,215 1,380 1,836 1,820 1.14% 0.19% 0.50% 22.09% 9.01% 0.77% 1.32% 0.53% 0.39% 28.84% 1.22% 1.47% 0.61% 18.01% 0.36% 1.37% 1.14% 1.16% 1.17% 4.05% 0.67% 1.11% 0.14% 0.44% 14.84% 7.56% 0.71% 1.09% 0.26% 0.29% 21.69% 1.11% 1.45% 0.52% 12.41% 0.21% 1.38% 1.09% 1.10% 1.06% 3.31% 0.66% 5.18% 0.64% 1.08% 79.69% 22.13% 1.22% 3.95% 3.17% 1.33% 84.40% 2.27% 1.53% 1.44% 64.55% 1.69% 1.39% 1.55% 1.73% 1.45% 11.06% 0.77% 0.25% 0.25% 0.27% N/A 0.03% 0.13% 0.01% 0.09% 0.16% 0.00% 0.03% 0.04% 0.01% 0.08% 0.15% 0.00% 0.07% 0.86% 0.00% 0.16% 0.25% 0.00% N/A 0.02% 0.45% 0.03% 0.01% 0.41% 0.03% 0.17% 0.84% 0.00% N/A 0.06% 0.02% 0.32% N/A 0.00% 0.18% 0.19% 0.20% 0.77% 0.08% 0.00% 0.16% 0.17% 0.20% 0.52% 0.09% 0.00% 0.37% 0.41% 0.22% 3.27% 0.00% <2.0 <2.0 <1.0 22.00 7.32 <4.0 1.60 <1.0 <2.0 87.00 <4.0 2.18 <1.0 12.70 <2.0 0.50 0.10 <5.0 1.80 1.30 <4.0 25 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary CHEMICAL NAME (Threshold in u.g/L) 1 ,3-Dichloropropane (N/A) 2,2-Dichloropropane (N/A) 1 , 1 -Dichloropropene (N/A) 1,3- Dichloropropene (HRL=40) Ethyl Benzene (MCL=700) Hexachlorobutadiene (HRL=0.9) Isopropylbenzene (N/A) m -Dichlorobenzene (HAL=600) m-Xylene (N/A) n-Butylbenzene (N/A) n-Propylbenzene (N/A) Naphthalene (HRL=140) o-Chlorotoluene (MCL=100) o-Dichlorobenzene (MCL=600) o-Xylene (N/A) p-Chlorotoluene (MCL=100) p-Dichlorobenzene (MCL=750) p-Isopropyltoluene (N/A) p-Xylene (N/A) sec-Butylbenzene (N/A) Styrene (MCL=100) tert-Butylbenzene (N/A) 1,1,1,2- Tetrachloroethane (HAL=70) 1 ,1 ,2,2-Tetrachloroethane (HAL =2) Tetrachloroethylene (MCL=5) Toluene (MCL=100) trans- 1,2-Dichloroethene (MCL=100) trans- 1,3-Dichloropropene (N/A) 1 ,2,3-Trichlorobenzene (N/A) 1 ,2,4-Trichlorobenzene (MCL=70) 1,1,1 -Trichloroethane (MCL=200) Total # PWS 16,947 16,757 16,947 9,164 20,081 12,284 12,771 20,429 11,329 12,763 12,724 13,452 15,721 19,953 13,987 15,612 15,494 12,167 10,127 12,343 16,623 12,353 16,956 20,407 19,814 20,089 19,945 9,883 12,876 13,449 15,279 #GW PWS 15,338 15,138 15,332 8,303 18,355 10,980 11,480 18,752 10,145 11,471 11,440 12,034 14,154 18,300 12,638 14,057 14,284 10,953 8,956 11,071 14,938 11,081 15,338 18,693 18,298 18,364 18,267 9,017 11,567 11,996 14,191 #SW PWS 1,748 1,754 1,749 898 1,884 1,385 1,359 1,819 1,276 1,371 1,363 1,502 1,702 1,795 1,450 1,689 1,334 1,282 1,230 1,337 1,832 1,337 1,753 1,867 1,652 1,887 1,825 959 1,389 1,539 1,213 % PWS >MRL 0.12% 0.15% 0.13% 0.16% 1.62% 0.35% 0.27% 0.25% 1.55% 0.35% 0.33% 1.18% 0.20% 0.28% 1.76% 0.17% 1.25% 0.25% 1.58% 0.23% 0.57% 0.19% 0.18% 0.45% 3.33% 3.50% 0.64% 0.25% 0.49% 0.49% 3.66% % GW PWS >MRL 0.12% 0.14% 0.10% 0.12% 1.40% 0.30% 0.28% 0.20% 1.47% 0.29% 0.34% 1.08% 0.16% 0.20% 1.69% 0.15% 1.11% 0.26% 1.49% 0.23% 0.45% 0.19% 0.13% 0.39% 3.38% 3.10% 0.59% 0.13% 0.46% 0.45% 3.57% % SW PWS >MRL 0.11% 0.23% 0.40% 0.56% 3.66% 0.72% 0.22% 0.77% 2.12/0 0.88% 0.22% 1.93% 0.53% 1.00% 2.41% 0.36% 2.70% 0.08% 2.36% 0.22% 1.53% 0.22% 0.63% 1.02% 2.66% 7.31% 1.10% 1.36% 0.72% 0.78% 4.62% % PWS > Threshold % GW PWS> Threshold % SW PWS> Threshold N/A N/A N/A 0.00% 0.00% 0.11% 0.00% 0.00% 0.06% 0.00% 0.00% 0.51% N/A 0.00% 0.00% 0.00% N/A N/A N/A 0.01% 0.00% 0.00% 0.02% 0.00% 0.00% 0.00% 0.00% 0.00% N/A 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A N/A N/A 0.00% 0.00% 0.00% N/A 0.00% 0.05% 0.91% 0.00% 0.01% 0.00% 0.05% 0.93% 0.00% 0.01% 0.00% 0.11% 0.67% 0.00% 0.00% N/A N/A 0.00% 0.03% 0.00% 0.03% 0.00% 0.00% 99% Value (MS/L) <1.0 <2.0 <1.0 <1.0 <5.0 <5.0 <2.0 <5.0 <4.0 <2.0 <2.0 <5.0 <1.0 <5.0 <5.0 <1.0 <4.4 <2.0 <5.0 <2.0 <2.0 <2.0 <1.0 <1.0 13.2 0.7 <1.0 <1.0 <5.0 <5.0 3.7 26 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary CHEMICAL NAME (Threshold in u.g/L) 1 , 1 ,2-Trichloroethane (MCL=5) Trichloroethylene (MCL=5) Trichlorofluorom ethane (HAL=175) 1 ,2,3-Trichloropropane (MCL=40) 1 ,2,4-Trim ethylbenzene (N/A) 1, 3, 5-Trim ethylbenzene (N/A) Vinyl Chloride (MCL=2) Xylenes (Total) (MCL=10,000) Total # PWS 19,964 15,290 16,851 17,392 12,755 12,671 15,184 9,463 #GW PWS 18,253 14,198 15,347 15,771 11,462 11,379 14,099 8,841 #SW PWS 1,853 1,220 1,637 1,758 1,372 1,370 1,209 670 % PWS >MRL 0.43% 3.54% 1.48% 0.25% 0.83% 0.61% 0.50% 3.04% % GW PWS >MRL 0.29% 3.37% 1.39% 0.25% 0.76% 0.59% 0.44% 2.51% % SW PWS >MRL 1.78% 5.66% 2 32% 0.23% 1.38% 0.66% 1.24% 10.75% % PWS > Threshold 0.04% 0.98% 0.01% 0.01% % GW PWS> Threshold 0.02% 1.00% 0.01% 0.01% % SW PWS> Threshold 0.16% 0.66% 0.00% 0.00% N/A N/A 0.28% 0.00% 0.23% 0.00% 0.83% 0.00% 99% Value (MS/L) <1.0 20.8 0.6 <2.0 <2.0 <2.0 <2.0 0.6 1 The high occurrence of Ethylene Dibromide are, in part, considered false positives related to analytical methods problems. MCL=Maximum Contaminant Level HAL=Health Advisory Level (as of December 2000) HRL=Health Reference Level (concentration values used only as reference levels for analyses in this report) MRL=Minimum Reporting Level The MCL, HAL, HRL, and MRL values are used in this report only as reference levels to facilitate occurrence assessments. "% PWS > Threshold" indicates the proportion of systems with any analytical results exceeding the concentration value of the HRL/MCL/HAL. (Note that results for % PWSs greater than an MCL value does not indicate a MCL violation. A formal MCL violation occurs when the MCL is exceeded by the average of four consecutive quarterly samples or confirmation samples as required by the primacy States.) N/A= There is no HRL/MCL/HAL available V.B. SDWIS/FED (Round 2) Contaminant Occurrence Table V.B.I summarizes the occurrence data of the SDWIS/FED (Round 2) 20 cross-section states for the 48 Round 2 contaminants. This table presents the total number of unique public water systems, the percent of public water systems with at least one result greater than the MRL, the percent of public water systems with at least one result greater than the MCL/HRL/HAL and, finally, the 99th percentile value in micrograms per liter (• g/L). (To review a map of the SDWIS/FED Round 2 cross- section states, refer to Figure III.B.S.b.) The 20 SDWIS/FED (Round 2) cross-section states reflect a significant national coverage: these states contain approximately 41% of public water systems nationally and 34% of the population served by public water systems. For a significant majority of the contaminants evaluated here (40 out of 48), less than 1% of public water systems in the cross-section states have analytical detections (any sample analytical result greater than the MRL). Two contaminants (dichlorodifluoromethane and trichlorofluoromethane) are detected in 1 to 2% of public water systems, as evidenced by one or more sample analytical results greater than the MRL, and 1 contaminant (chloromethane) is detected in 2.25% of public water systems, as evidenced by one or more sample analytical results greater than the MRL. Five contaminants -4 THMs and sulfate- have a considerably higher percent of systems with one or more sample analytical results greater than the MRL (ranging from 12.12% to 27.42% for the THMs and 88.11% for sulfate). Select SDWIS/FED (Round 2) high occurrence contaminants are identified and briefly assessed in Section VI. 27 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Table V.B.I. SDWIS/FED (Round 2) Data - 20 State Cross-Section Summary of Occurrence CHEMICAL NAME (Threshold in ug/L) Total PWS #GW PWS #SW PWS % PWS >MRL % GW PWS % sw PWS % PWS > Threshol % GW PWS> % SW PWS> 99% Value IOCS Sulfate (HRL=500,000) 16,495 15,009 1,486 88.11% 87.76% 91.66% 1.79% 1.83% 1.41% 560000 SOCs Aldicarb1 (HRL=7) Aldicarb Sulfone1 (HRL=7) Aldicarb Sulfoxide1 (HRL=7) Aldrm1 (HRL =0.002) Butachlor1 (N/A) Carbaryl1 (MCL=700) Dicamba1 (MCL=200) Dieldrm1 (HRL =0.002) 3-Hydroxycarbofuran1 (N/A) Methomyl1 (MCL=200) Metolachlor1 (HRL =70) Metribuzin1 (HRL=91) Propachlor1 (MCL=90) 11,972 11,968 11,954 11,745 11,940 12,623 14,034 11,788 12,644 12,604 12,953 13,512 12,050 10,509 10,512 10,500 10,420 10,482 11,086 12,220 10,329 11,088 11,068 11,503 11,833 10,600 1,463 1,456 1,454 1,325 1,458 1,537 1,814 1,459 1,556 1,536 1,450 1,679 1,450 0.01% 0.08% 0.08% 0.01% 0.04% 0.03% 0.34% 0.09% 0.07% 0.07% 0.83% 0.01% 0.05% 0.00% 0.04% 0.03% 0.01% 0.01% 0.02% 0.21% 0.09% 0.02% 0.05% 0.11% 0.01% 0.02% 0.07% 0.41% 0.48% 0.00% 0.27% 0.13% 1.21% 0.14% 0.45% 0.20% 6.55% 0.00% 0.28% 0.00% 0.00% 0.01% 0.01% 0.00% 0.00% 0.01% 0.01% 0.00% 0.00% 0.00% 0.00% N/A 0.00% 0.00% 0.09% 0.00% 0.00% 0.09% 0.00% 0.00% 0.14% N/A 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% <3.0 <2.0 <4.0 <2.0 <10.0 <10.0 <10.0 <1.0 <10.0 <50.0 <5.0 <2.0 <5.0 VOCs Bromobenzene (N/A) Bromochlorom ethane2 (MCL=10) Bromodichlorom ethane (HRL =60) Bromoform (HRL=400) Bromom ethane (MCL=10) Chloroethane (N/A) Chloroform (HRL=600) Chlorom ethane (MCL=3) Dibromochlorom ethane (HRL =60) Dibromom ethane (N/A) Dichlorodifluorom ethane2 (MCL=1,000) 1 , 1 -Dichloroe thane (MCL=5) 1 ,3-Dichloropropane (N/A) 2,2-Dichloropropane (N/A) 1 , 1 -Dichloropropene (N/A) 24,125 22,974 23,858 18,461 23,328 24,433 23,737 23,478 23,750 23,006 22,141 24,808 24,065 24,096 24,069 21,461 20,507 21,152 16,348 20,872 21,925 21,021 21,030 21,059 20,454 19,836 22,114 21,430 21,445 21,438 2,664 2,467 2,706 2,113 2,456 2,508 2,716 2,448 2,691 2,552 2,305 2,694 2,635 2,651 2,631 0.13% 0.46% 21.97% 12.12% 0.75% 0.34% 27.42% 2.25% 18.37% 0.46% 1.27% 0.74% 0.06% 0.09% 0.07% 0.12% 0.32% 16.14% 11.08% 0.74% 0.32% 21.84% 2.04% 14.55% 0.32% 1.23% 0.67% 0.05% 0.07% 0.06% 0.23% 1.62% 67.52% 20.11% 0.86% 0.56% 70.54% 4.08% 48.23% 1.53% 1.65% 1.34% 0.11% 0.26% 0.15% N/A 0.03% 0.08% 0.01% 0.06% 0.02% 0.05% 0.00% 0.05% 0.08% 0.30% 0.05% 0.08% N/A 0.04% 0.58% 0.08% 0.01% 0.55% 0.05% 0.26% 0.78% 0.30% N/A 0.00% 0.08% 0.00% 0.07% 0.00% 0.11% N/A N/A N/A <1.0 <1.0 18.8 6.5 <9.0 <2.5 110.0 <2.5 9.7 <1.0 <20.0 <1.0 <2.0 <1.0 <1.0 28 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary CHEMICAL NAME (Threshold in ug/L) 1,3- Dichloropropene (HRL=40) Hexachlorobutadiene2 (HRL=0.9) Isopropylbenzene2 (N/A) m -Dichlorobenzene (HAL=600) n-Butylbenzene2 (N/A) n-Propylbenzene2 (N/A) Naphthalene2 (HRL=140) o-Chlorotoluene (MCL=100) p-Chlorotoluene (MCL=100) p-Isopropyltoluene2 (N/A) sec-Butylbenzene2 (N/A) tert-Butylbenzene2 (N/A) 1,1, 1 ,2-Tetrachloroethane (HAL=70) 1 ,1 ,2,2-Tetrachloroethane (HAL =2) 1 ,2,3-Trichlorobenzene2 (N/A) Trichlorofluorom ethane2 (HAL=175) 1 ,2,3-Trichloropropane (MCL=40) 1 ,2,4-Trim ethylbenzene2 (N/A) 1, 3, 5-Trim ethylbenzene2 (N/A) Total PWS 16,787 22,736 22,995 24,119 22,972 22,969 22,923 24,118 21,378 22,617 22,973 22,973 24,127 24,800 22,532 22,659 24,088 22,965 22,974 #GW PWS 15,178 20,380 20,524 21,457 20,509 20,501 20,524 21,457 18,808 20,320 20,509 20,508 21,462 22,106 20,144 20,329 21,441 20,504 20,513 #SW PWS 1,609 2,356 2,471 2,662 2,463 2,468 2,399 2,661 2,570 2,297 2,464 2,465 2,665 2,694 2,388 2,330 2,647 2,461 2,461 % PWS >MRL 0.35% 0.18% 0.24% 0.26% 0.13% 0.23% 0.75% 0.14% 0.12% 0.16% 0.14% 0.11% 0.21% 0.08% 0.19% 1 . 1 7% 0.08% 0.76% 0.43% % GW PWS 0.32% 0.13% 0.23% 0.22% 0.12% 0.19% 0.62% 0.11% 0.10% 0.15% 0.14% 0.10% 0.16% 0.05% 0.15% 0.93% 0.06% 0.63% 0.35% % sw PWS 0.62% 0.59% 0.32% 0.53% 0.20% 0.57% 1.92% 0.38% 0.27% 0.26% 0.20% 0.16% 0.64% 0.30% 0.50% 3.22 /o 0.23% 1.79% 1 . 1 0% % PWS > Threshol 0.00% 0.02% % GW PWS> 0.00% 0.00% % sw PWS> 0.00% 0.13% N/A 0.00% 0.00% 0.00% N/A N/A 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A N/A N/A 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A N/A 99% Value <0.5 <1.0 <2.0 <1.0 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 <1.0 <1.0 <2.0 <2.5 <1.0 <1.0 <2.0 1. Massachusetts data not included in summary statistics for this contaminant. 2. New Hampshire data not included in summary statistics for this contaminant. MCL=Maximum Contaminant Level HAL=Health Advisory Level (as of December 2000) HRL=Health Reference Level (concentration values used only as reference levels for analyses in this report) MRL=Minimum Reporting Level The MCL, HAL, HRL, and MRL values are used in this report only as reference levels to facilitate occurrence assessments. "% PWS > Threshold" indicates the proportion of systems with any analytical results exceeding the concentration value of the HRL/MCL/HAL. (Note that results for % PWSs greater than an MCL value does not indicate a MCL violation. A formal MCL violation occurs when the MCL is exceeded by the average of four consecutive quarterly samples or confirmation samples as required by the primacy States.) N/A= There is no HRL/MCL/HAL available 29 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary VI. ASSESSMENTS OF SELECT HIGH OCCURRENCE CONTAMINANTS VI.A. Select High Occurrence Contaminants and Detailed Graphical and Spatial Analysis The contaminants in URCIS (Round 1) and SDWIS/FED (Round 2) were ranked according to their occurrence as a means to select a group of high occurrence contaminants for a more detailed graphical and spatial assessments. These detailed assessments are included in Section VI of the compete National Occurrence report (Occurrence of Unregulated Contaminants in Public Water Systems: An Initial Assessment, EPA 815-P-00-001). This summary report provides only a description of the types of assessments included in the complete report. The ranking of the URCIS (Round 1) contaminant occurrence data is presented in Table VI. A. 1, and the ranking of SDWIS/FED (Round 2) data is presented in Table VI.A.2. The contaminants were ranked by percent of systems with at least one sample detection (at least one sample analytical result greater than the minimum reporting level) and by percent of systems with at least one sample analytical result greater than the MCL or HAL or HRL (whichever MCL/HAL/HRL health effects threshold is relevant to the contaminant in question). Table VI.A.3 identifies the high occurrence contaminants selected for detailed assessments. High occurrence was the primary consideration for selection for the detailed assessments included in the complete National Occurrence report, but consideration was also given to coverage across contaminant groups, changing regulatory status between Rounds 1 and 2, and overlap between Rounds 1 and 2. Table VI.A.1. Contaminant Occurrence Ranking of URCIS (Round 1) Data Percent Systems With At Least One Sample Analytical Detection SOCs iDibromochloropropane X Ip.thvlene Dihromid^^^^ ^^_ 2.49% 1 14% VOCs X X X X X Chloroform Bromodichlorom ethane Dibromochloromethane Bromoform Dichloromethane 1,1,1 -Trichloroethane Trichloroethylene Toluene Tetrachloroethylene Xylenes (Total) o-Xylene Ethyl Benzene p-Xylene m-Xylene rrichlorofluorom ethane cis- 1 ,2-Dichloroethene Dichlorodifluoromethane Carbon Tetrachloride p-Dichlorobenzene Chloromethane Naphthalene Dichloroethene 1,2-Dichloroethane Benzene 1 1 -nir.hlnrne: thane: 28.63% 22.09% 17.87% 8.95% 4.05% 3.66% 3.54% 3.50% 3.33% 3.04% 1.76% 1.62% 1.58% 1.55% 1.48% 1.47% 1.37% 1.32% 1.25% 1.22% 1.18% 1.17% 1.16% 1.14% 1 14% Percent Systems With At Least One Sample Analytical Result Greater than MCL/HAL/HRL SOCs Dibromochloropropane X F.thvlene Dihromide 1.32% 0 16% VOCs X Trichloroethylene X Tetrachloroethylene Dichloromethane X Chloromethane Vinyl Chloride Benzene Dichloroethene 1,2-Dichloroethane X 1,1-Dichloroethane Carbon Tetrachloride Bromodichloromethane Hexachlorobutadiene Bromomethane 1,2-Dichloropropane Dibromochloromethane 1 , 1 ,2,2-Tetrachloroethane 1 , 1 ,2-Trichloroethene Bromochlorom ethane cis-l,2-Dichloroethene 1,1, 1 -Trichloroethane X Chloroform Naphthalene Trichlorofluoromethane 1,2,3-Trichloropropane Rrnm nfnrm 0.98% 0.91% 0.77% 0.45% 0.28% 0.25% 0.20% 0.19% 0.18% 0.16% 0.13% 0.11% 0.09% 0.08% 0.06% 0.05% 0.04% 0.03% 0.03% 0.03% 0.02% 0.01% 0.01% 0.01% 0 0 1 % 30 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Percent Systems With At Least One Sample Analytical Detection 1,2,4-Trimethylbenzene Bromomethane 1,2-Dichloropropane trans- 1 ,2-Dichloroethene cis- 1 ,2-Dichloropropene 1,3,5-Trimethylbenzene Styrene Chlorobenzene Bromochloromethane Vinyl Chloride 1 ,2, 4-Tri chlorobenzene 1, 2, 3-Tri chlorobenzene 1,1,2,2-Tetrachloroethane 1 , 1 ,2-Trichloroethene Chloroethane Dibromomethane n-Butylbenzene Hexachlorobutadiene n-Propyulbenzene o-Dichlorobenzene Isopropyltoluene 1,2,3-Trichloropropane trans- 1,3-Dichloropropene m-Dichlorobenzene p-Isopropyltoluene sec-Butylbenzene o-Chlorotoluene Bromobenzene tert-Butylbenzene 1,1, 1 ,2-Tetrachloroethane p-Chlorotoluene 1,3-Dichloropropene 2,2-Dichloropropane 1 , 1 -Dichloropropene 1 ^-Fiir.lilnrnnrnnanR 0.83% 0.77% 0.67% 0.64% 0.61% 0.61% 0.57% 0.53% 0.50% 0.50% 0.49% 0.49% 0.45% 0.43% 0.39% 0.36% 0.35% 0.35% 0.33% 0.28% 0.27% 0.25% 0.25% 0.25% 0.25% 0.23% 0.20% 0.19% 0.19% 0.18% 0.17% 0.16% 0.15% 0.13% ft 19% X = Contaminants selected for graphical/spatial assessment in N/A = There is no Health Reference Level (HRL), Maximum the contaminants. Percent Systems With At Least One Sample Analytical Result Greater than MCL/HAL/HRL trans- 1 ,2-Dichloroethene Toluene Xylenes (Total) Ethyl Benzene Dichlorodifluorom ethane p-Dichlorobenzene Styrene Chlorobenzene 1,2,4-Trichlorobenzene o-Dichlorobenzene m-Dichlorobenzene o-Chlorotoluene 1,1, 1 ,2-Tetrachloroethane p-Chlorotoluene 1,3-Dichloropropene 1,3-Dichloropropane 1 , 1 -Dichloropropene 1,2,3-Trichlorobenzene 1,2,4-Trimethylbenzene 1,3,5-Trimethylbenzene 2,2-Dichloropropane Bromobenzene Chloroethane cis-l,2-Dichloropropene Dibromomethane Isopropyltoluene m-Xylene n-Butylbenzene n-Propyulbenzene o-Xylene p-Isopropyltoluene p-Xylene sec-Butylbenzene tert-Butylbenzene tran«-1 ^-Fiip.VilnrnnrnnpnR 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A XT/ A complete National Occurrence report. Contaminant Level (MCL), or Health Advisory Level (HAL) for Table VI.A.2. Contaminant Occurrence Ranking of SDWIS/FED (Round 2) Data Percent Systems With At Least One Sample Analytical Detection SOCs X X X Metolachlor Dicamba Dieldrin Aldicarb Sulfoxide Aldicarb Sulfone Methomyl 3 -Hydroxycarbofuran Propachlor Butachlor Carbaryl Aldrin Aldicarb N/tfitrihiiyin 0.83% 0.34% 0.09% 0.08% 0.08% 0.07% 0.07% 0.05% 0.04% 0.03% 0.01% 0.01% ft ft l % Percent Systems With At Least One Sample Analytical Result Greater than MCL/HAL/HRL SOCs X X X Dieldrin Aldrin Aldicarb Sulfoxide Metribuzin Aldicarb Carbaryl Propachlor Methomyl Aldicarb Sulfone Dicamba Metolachlor Butachlor ^-WvHrnwr.arhnfiiran 0.09% 0.01% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A XT/ A 31 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Percent Systems With At Least One Sample Analytical Detection VOCs X X X Chloroform Bromodichlorom ethane Dibromochloromethane Bromoform Chloromethane Dichlorodifluoromethane rrichlorofluorom ethane 1,2,4-Trimethylbenzene Naphthalene Bromomethane 1 , 1 -Dichloroethane Bromochloromethane Dibromom ethane 1,3,5-Trimethylbenzene 1,3-Dichloropropene Chloroethane m-Dichlorobenzene Isopropylbenzene n-Propylbenzene 1,1, 1 ,2-Tetrachloroethane 1,2,3-Trichlorobenzene Hexachlorobutadiene p-Isopropyltoluene sec-Butylbenzene o-Chlorotoluene Bromobenzene n-Butylbenzene p-Chlorotoluene tert-Butylbenzene 2,2-Dichloropropane 1,2,3-Trichloropropane 1,1,2,2-Tetrachloroethane 1 , 1 -Dichloropropene 1 .3-Dichloronronane 27.42% 21.97% 18.37% 12.12% 2.25% 1.27% 1.17% 0.76% 0.75% 0.75% 0.74% 0.46% 0.46% 0.43% 0.35% 0.34% 0.26% 0.24% 0.23% 0.21% 0.19% 0.18% 0.16% 0.14% 0.14% 0.13% 0.13% 0.12% 0.11% 0.09% 0.08% 0.08% 0.07% 0.06% Percent Systems With At Least One Sample Analytical Result Greater than MCL/HAL/HRL VOCs X X X Chloromethane 1 , 1 -Dichloroethane Dibromochloromethane Bromodichlorom ethane Bromomethane Chloroform Bromochloromethane Hexachlorobutadiene Bromoform 1,2,3-Trichloropropane 1,1,1 ,2-Tetrachloroethane 1 , 1 ,2,2-Tetrachloroethane 1,3-Dichloropropene Dichlorodifluoromethane m-Dichlorobenzene Naphthalene o-Chlorotoluene p-Chlorotoluene Trichlorofluorom ethane 1 , 1 -Dichloropropene 1,2,3-Trichlorobenzene 1,2,4-Trimethylbenzene 1,3,5-Trimethylbenzene 1,3-Dichloropropane 2,2-Dichloropropane Bromobenzene Chloroethane Dibromomethane Isopropylbenzene n-Butylbenzene n-Propylbenzene p-Isopropyltoluene sec-Butylbenzene tert-Butvlhen/ene 0.58% 0.08% 0.08% 0.08% 0.06% 0.04% 0.03% 0.02% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A X= Contaminants selected for graphical/spatial assessment in N/A = There is no Health Reference Level (HRL), Maximum complete National Occurrence report. Contaminant Level (MCL), or Health Advisory Level (HAL) for Table VI.A.3. High Occurrence Contaminants Selected for Graphical and Spatial Assessments (and some characteristics considered in the selection). Contaminant Trichloroethylene Tetrachloroethylene Chloromethane 1 , 1 -Dichloroethane Chloroform Ethylene Dibromide Dieldrin Aldicarb Sulfoxide Metolachlor Regulated (Round 2) (Round 2) (Round 2) Unregulated • • • . . • • • • voc • • • . . soc • • • • THM • URCIS (Round 1) • • • . • • SDWIS/ FED (Round 2) • . . • • • 32 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary VLB. Graphical and Spatial Assessments of Select High Occurrence Contaminants The detailed graphical and spatial assessments of the high occurrence contaminants identified above are included in Section VLB.of the complete National Occurrence report. These assessments, evaluated together with the analytical results tables presented throughout the complete National Occurrence report and report appendices, provide a comprehensive overview of the degree, distribution, and temporal trends (if any) of contaminant occurrence. The graphical and spatial assessments are conducted to provide additional analytical detail for the select high occurrence contaminants (of potentially greater regulatory interest), and to provide examples of graphical and spatial assessments that can be conducted for any other contaminants of interest. For contaminants of lower occurrence, however, the data maybe too sparse to support these types of assessments. One important aspect of the cross-section state data must be considered as part of any conclusions drawn from the maps and graphs in the complete National Occurrence report and this national summary. The national cross-sections have been developed from public water systems' contaminant monitoring data with the intent that, in aggregate, the cross-section states' occurrence findings are indicative of national occurrence. Given that half (or more) of the states are without adequate data (and therefore could not be included in the cross-sections used for analyses), sub-national occurrence findings, such as regional or multi-state patterns, may be difficult to characterize and must be interpreted with caution. Supplemental information should be collected and used, whenever possible, to assist in evaluating the significance of any apparent or suggested regional patterns. To provide the broadest possible geographic coverage, some occurrence maps are presented that use all available data from all states with data in URCIS (Round 1) and/or SDWIS/FED (Round 2) (see the complete National Occurrence report Section V.I., Figures VI.B.I.a, VI.B.2.a, VLB.3.a, VLB.4.a, VLB.5.a, VLB.6.a, VLB.7.a, and VLB.8.a). This use of all data, including incomplete state data sets, and "biased" state data sets is only appropriate for broad, simple identifications of presence or absence of a detection of a specific contaminant. This more extensive use of the data in the databases can be appropriate when a simple identification of states with any PWS contaminant detection is of interest. The biased data used in these figures are not and cannot be used for any national estimates of contaminant occurrence. The remaining, majority of figures presented in the complete National Occurrence report have been based only on non-biased, representative cross-section state data, and are used to characterize the distribution of contaminant occurrence. For example, the cross-section state data are used to develop maps that categorize states as based on the range of percent of state PWSs with detections of a particular contaminant (see Figures VI.B.l.b., VI.B.2.b, VI.B.S.b, VI.BAb, VI.B.5.b, VI.B.6.b, VI.B.T.b, andVI.B.S.b). Additionally, the temporal distribution of the percent of systems with contaminant detections, or the percent of systems with sample results of contaminants identified above the MCL (or HRL) by year are presented in Figures VLB.I.e., VI.B.2.C, VI.B.3.C, VI.BAc, VI.B.5.C, VI.B.6.C, VI.B.T.d, VI.B.S.d, andVI.B.9.a. VI.B.l. Ethylene Dibromide A spatial assessment of contaminant occurrence using URCIS (Round 1) data for ethylene dibromide suggests a widespread occurrence. However, there is no apparent spatial/geographic occurrence pattern within the wide extent of occurrence. 33 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary In temporal assessments of ethylene dibromide occurrence, there appears to be a steady but slight decrease in the percent of public water systems with ethylene dibromide detections (analytical results greater than the MRL) from 1988 to 1992. There is also a less consistent, but apparent decrease in the percent of public water systems with analytical results greater than the MCL during the same time period (1988 to 1992). VI.B.2. Tetrachloroethylene Tetrachloroethylene (sometimes referred to as perchloroethylene, or 'perc', or PCE) is also of very widespread occurrence and with no apparent spatial occurrence pattern. (Also noted is the well- established co-occurrence of this contaminant with trichloroethylene.) In temporal assessments of occurrence, there may be a decrease in the percent of public water systems with detections and with analytical results greater than the MCL for the 1988 to 1992 period. However, the percent of public water systems increases for both measures (detections and MCL exceedances) in 1992. Note, however, that unavailable state data may affect interpretation of temporal trends. VI.B.3. Trichloroethylene The occurrence overview of trichloroethylene (sometimes referred to as TCE) is similar to that of tetrachloroethylene. Trichloroethylene is also of very widespread occurrence and with no apparent spatial occurrence pattern. (Also noted is the well-established co-occurrence of this contaminant with tetrachloroethylene.) Also, in temporal assessments of occurrence, there may be a decrease in the percent of public water systems with detections and with analytical results greater than the MCL for the 1988 to 1992 period. However, the percent of public water systems increases for both measures (detections and MCL exceedances) in 1992. Note, however, the same caution regarding unavailable state data possibly affecting interpretation of temporal trends. VI.B.4. Aldicarb Sulfoxide A review of the aldicarb sulfoxide illustrates some of the interpretive cautions mentioned previously. The spatial assessment based on SDWIS/FED Round 2 data suggests that aldicarb sulfoxide detections are more evident in northern states (likely related to specific farm crops and pesticide use). Higher percentages of public water systems with detections (analytical results greater than the MRL) are indicated in Michigan, Missouri, Washington, and Oregon. Only Oregon is present in the category of highest percentage of public water systems with analytical results of aldicarb sulfoxide greater than the HRL. However, three states (Florida, New York, and Wisconsin) with known, historic problems with aldicarb sulfoxide in groundwater do not have data in the SDWIS/FED (Round 2) database. Apparent spatial and geographic patterns must be viewed and interpreted carefully. Any conclusions made regarding the geographic patterns (or lack of patterns) of occurrence must consider this reality of missing data coverage. In the temporal assessment, a "spike" (a significant but short-lived increase) in 1996 in the percent of public water systems with analytical results greater than the HRL appears significant, but 34 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary actually reflects a very small increase in the number of systems. Therefore, there is no temporal trend, with occurrence remaining relatively low from 1992 to 1997. VI.B.5. Dieldrin Dieldrin detections appear to be limited to states south of a line extending between Texas and Massachusetts (though there are many states without dieldrin data). Although occurrence appears high in 1992 with a subsequent drop, occurrence data for 1992 was sometimes inconsistently reported since that year marks the divide between the Round 1 and Round 2 monitoring periods. The implementation of the SDWA 1993 amendments may influence any occurrence findings critically centered around the 1992 and 1993 data. VI.B.6. Metolachlor Metolachlor also appears to be of widespread, but generally low, occurrence. However, many states did not report metolachlor data. This is especially important given that the cornbelt states with the highest metolachlor use (Indiana, Illinois, and Iowa) do not have any metolachlor data in the SDWIS/FED (Round 2) data. In this case, supplemental information is needed to more fully assess the national occurrence of metolachlor. VI.B.7. 1,1-Dichloroethane Data are available from both Round 1 and Round 2 for 1,1-dichloroethane. Using only cross- section state data, 32 of the 34 combined cross-section states have public water systems with at least one detection of 1,1-dichloroethane. An expanded use of available data shows that 42 of the 46 states with data (which includes cross-section as well as any available non-cross-section state data) have public water systems with at least one detection of 1,1-dichloroethane. The biased (non-cross-section state) data can be used here to expand the spatial coverage. Based on the percentage of PWSs with analytical results greater than the detection limit, there appears to be generally higher levels of occurrence in states east of the Mississippi River. Again, supplemental information would be necessary to make definitive conclusions on 1,1-dichloroethane occurrence distributions. Regarding temporal trends, there appears to be a decrease in the occurrence of 1,1- dichloroethane from 1986 to 1997 when based on either percent PWSs with analytical results greater then the detection limit or greater than the MCL. Comparisons were also made for 1,1-dichloroethane occurrence between Round 1 to Round 2 for the 8 states with data in both sampling rounds. With occurrence based on the detection limit, no consistent temporal trend is suggested. When occurrence is based on MCLs, there is an apparent decreasing trend of 1,1-dichloroethane occurrence in 4 of the 8 states (with the other 4 states indicating no occurrence in either rounds). These results seem to at least partially corroborate the decreasing occurrence trend over time indicated above. VI.B.8. Chloromethane Detections and distribution of chloromethane are addressed with maps and graphs similar to those for 1,1-dichloroethane. Chloromethane is of widespread and relatively high levels of occurrence. 35 ------- EPA - OGWDW Occurrence of Unregulated Contaminants in Public Water Systems - A National Summary Temporally, occurrence may have decreased from 1988 to 1992, but in later years appears to be increasing, based on percent public water systems with detections. The occurrence of chloromethane appears to be stable, based on percent public water systems with analytical results greater than the MCL. VI.B.9. Chloroform Chloroform is evaluated only temporally. Occurrence for chloroform, as is typical of the THMs, is relatively high based on the percent of systems with analytical detections. In contrast, the occurrence of chloroform in public water systems greater than the HRL are relatively low. Also, chloroform occurrence appears to increase from Round 1 to Round 2. VLB. 10. Comparison of Occurrence in URCIS (Round 1) and SDWIS/FED (Round 2) Occurrence data for three contaminants were contained in both Round 1 and Round data sets: chloromethane, 1,1-dichloroethane, and chloroform. Review of the data suggest no distinct or apparent temporal trends between occurrence of these three contaminants between the periods of URCIS (Round 1) and SDWIS/FED (Round 2) monitoring. 36 ------- |