Policy Analysis Brief Survey of EPA Standard-Setting and Health Assessment TIMOTHY C. BENNER* United States Environmental Protection Agency, Office of Research and Development, Office of Science Policy, 1200 Pennsylvania Avenue NW (8104R), Washington, DC 20460
The Environmental Protection Agency (EPA) promulgates standards for air pollutants and drinking water contaminants, as part of its mandate to protect public health and welfare. The Agency also assesses the health risks associated with hundreds of chemical substances, often developing quantitative toxicity and cancer potency benchmarks. This article compares EPA standards and benchmark values to those of other countries and other agencies. This includes the national ambient air quality standards (NAAQS), the national primary drinking water regulations (NPDWR), and benchmark values from the Integrated Risk Information System (IRIS). Results show that the NAAQS are generally comparable to or less strict than the air quality standards of other countries and international organizations. The NPDWR tend to be less strict than the water quality standards of other countries for inorganic chemicals, and they are more strict about as often as they are less strict for organic chemicals. Reference values for toxicity and cancer potency derived in EPA health assessments posted in the IRIS database are less stringent than those of other agencies about as often as they are more stringent, and they are often identical. Revisions to these values more often than not made them less stringent. These results suggest that EPA’s standards and quantitative health assessments are not out of line with those of other agencies and other countries.
Introduction The mission of the Environmental Protection Agency (EPA) is “to protect human health and the environment” (1). An important part of protecting human health is limiting human exposure to harmful substances, both man-made and natural. Under a variety of environmental statutes, the EPA is required to set standards for pollutants in the air, contaminants in drinking water, and pesticides in food, based on the best available science as well as other factors. The EPA promulgates these standards as federal regulations and works with state, local, tribal, and private partners to implement them. Of course, the authority and responsibility for setting environmental standards places the EPA in a somewhat unenviable position. Critics at both ends of the political spectrum as well as those with differing scientific opinions are often dissatisfied with the EPA’s decisions. Environmental groups, public health groups, and some politicians may argue that the EPA does not act quickly enough, that its standards are not strict enough, or that it underestimates environmental * Corresponding author phone: (202)564-6769; fax: (202)565-2911; e-mail:
[email protected]. 10.1021/es035132h Not subject to U.S. Copyright. Publ. 2004 Am. Chem. Soc. Published on Web 05/28/2004
health risks. Conversely, industry groups, trade groups, and other politicians may argue that the EPA acts without sufficient deliberation, that its standards are unnecessarily strict, or that it exaggerates public health risks. Part of this disagreement involves a perception or assertion of institutional bias: some groups may accuse the EPA of being too lax, while others may accuse the EPA of being deliberately too aggressive. Given this wide range of contentions, it may be informative to examine EPA standards and health assessments, in the context of comparable standards and assessments from around the world. A quantitative comparison would, at least, help inform the discussion. To that end, this article examines three components of the EPA’s efforts to protect public health: the U.S. national ambient air quality standards, compared to the air quality standards of other countries; the U.S. national primary drinking water regulations, compared to the water quality standards of other countries; and the EPA’s quantitative health benchmarks for chemical substances, specifically those conducted for the Integrated Risk Information System (IRIS), compared to the assessments of other agencies and to previous IRIS assessments as a measure of how they have changed over time. The goal is to provide a concise quantitative comparison, rather than an in-depth analysis of the policies of individual countries or organizations. The next section describes each of these three components. The subsequent section details the comparisons and presents the results. The last section discusses the results and offers some conclusions.
Regulatory Process The Clean Air Act (CAA; 42 U.S.C. 7401 et seq.) requires the EPA to establish national ambient air quality standards (NAAQS) for ubiquitous air pollutants that “endanger public health or welfare”. The CAA also requires the EPA to review and, if necessary, revise the standards every 5 years. For each pollutant, the EPA must develop the scientific criteria for setting or reviewing the standard, including effects on human health and the environment (e.g., refs 2 and 3). These criteria derive from a thorough compilation of relevant scientific research. Based on these criteria and on staff recommendations (e.g., refs 4 and 5), the Administrator selects a primary standard to protect public health and a secondary standard to protect the public welfare, e.g., ecosystems, agriculture, visibility, and infrastructure. The CAA requires that the primary standard allow an “adequate margin of safety”. Subsequent court decisions have interpreted this to preclude consideration of implementation costs in setting the standard (e.g., ref 6). Standards are published as legally enforceable limits in the Federal Register and, subsequently, the Code of Federal Regulations. The states and tribes, with EPA guidance, are responsible for developing plans to implement and attain the standards. The EPA also supports monitoring networks to measure pollutant levels for compliance purposes. The third column of Table 1 lists the current U.S. primary NAAQS (40 C.F.R. 50) for the six “criteria” pollutants: carbon monoxide (CO), nitrogen dioxide (NO2), ozone, lead, particulate matter (PM), and sulfur dioxide (SO2). Separate PM standards apply to particles smaller than 10 microns (PM10) and particles smaller than 2.5 microns (PM2.5). The Safe Drinking Water Act (SDWA) (42 U.S.C. 300f et seq.) requires the EPA to establish national primary drinking water regulations (NPDWR) limiting the concentration of VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Air Quality Standard Comparison air pollutant CO [mg/m3] NO2 [µg/m3] Ozone [µg/m3] Lead [µg/m3] PM10 [µg/m3] PM2.5 [µg/m3] SO2 [µg/m3] air pollutant CO [mg/m3] NO2 [µg/m3] Ozone [µg/m3] Lead [µg/m3] PM10 [µg/m3] PM2.5 [µg/m3] SO2 [µg/m3]
time
U.S.
CA
WHO
EU
Austria
France
Germany
Hungary
Netherlands
Spain
Sweden
U.K.
1h 8h annual
40 10 100
23 10
30 10 40
10 40
10 30
10 40
10 40
70
40
10 40
10 40
10 40
1h 8h quarter
235 157 1.5
180 120
120
110
110
110
120
120
110
120
24 h annual 24 h annual 24 h annual
150 50 65 15 365 80
50 20
50 20a
50 40
50 40
50 40
20
50 20a
50 40
50 40
125 50
125
120
125
125
125
125
100
125
150 70
time
Canada
Alberta
BC
Ontario
Quebec
Argentina
1h 8h annual
35 15 100
15 6 60
28 11
36.2 15.7
34 15 103
57 11
1h 8h quarter
160 127
160
157
196
CO [mg/m3] NO2 [µg/m3] Ozone [µg/m3] Lead [µg/m3] PM10 [µg/m3] PM2.5 [µg/m3] SO2 [µg/m3]
165
Australia
Brazil
China
Egypt
India
40 10 100
10
10 57
30 10
4 2 60
196
160
160
40 200 120
1.5
24 h annual 24 h annual 24 h annual
air pollutant
a
12 105
50
50
150 50
150 100
70
100 60
208 52
365 80
150 60
150 60
80 60
30 300 60
150 30
260 50
275 55
288 52
time
Japan
Mexico
N.Z.
Philippines
R.O.K.
1h 8h annual
23
12
30 10
35 10
29 10 94
1h 8h quarter
117
24 h annual 24 h annual 24 h annual
215
S. Africa
Thailand 34 10
94
140 60 1.5
196 118
235
200
1.5
150 100 0.2
100
150 50
50 20
150 60
150 70
180 60
120 50
104
339 80
120
180 80
130 52
260 80
300 100
Final 2010 limit.
contaminants in drinking water supplied from public water systems. Under this authority, the EPA has set standards for nearly 90 contaminants, including inorganic chemicals, disinfectants, disinfection byproducts, organic chemicals and pesticides, microorganisms, and radionuclides. The SDWA Amendments of 1996 require the EPA to establish and maintain a contaminant candidate list (CCL; 63 F.R. 10274), to identify possible drinking water problems and help set priorities in addressing them. The CCL lists contaminants which, at the time of its publication, are not subject to any proposed or promulgated NPDWR, are known or anticipated to occur in public water systems, and may require regulation. The SDWA directs the EPA to select five or more contaminants every 5 years from the current CCL for which regulation may present significant opportunities to reduce public health risk. For each of the selected contaminants, the EPA conducts a comprehensive review of relevant health research and, if a 3458
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regulation is determined to be necessary, sets a Maximum Contaminant Level Goal, which is the maximum level at which no adverse health effects are expected, with a margin of safety. Finally, the EPA considers technical feasibility and cost to develop a Maximum Contaminant Level (MCL), a legally enforceable standard promulgated in the Federal Register as part of the national primary drinking water regulations (NPDWR). The states and tribes, with EPA guidance, are responsible for implementing these regulations. The second column of Table 3 lists the current U.S. NPDWR (40 C.F.R. 141). In addition to setting standards for ambient pollutant concentrations, the EPA also regulates pollution emissions. The CAA mandates a great variety of air pollution control programs. Some of these are directly related to NAAQS implementation, such as requirements for reasonably available control technology and measures, new source perfor-
mance standards, and new source review. These programs are designed to help areas attain or maintain the NAAQS. Others may not be direct parts of the NAAQS implementation process, such as rules for interstate pollutant transport, power plant emission cap-and-trade, vehicle engine performance, and fuel composition, but they contribute to NAAQS attainment by reducing emissions of criteria air pollutants and their precursors. Still other programs are unrelated to the NAAQS, such as the technology-based standards to reduce hazardous air pollutant emissions and the phaseout of substances that deplete the stratospheric ozone layer. Likewise, the Federal Water Pollution Control Act (commonly known as the Clean Water Act; 33 U.S.C. 1251 et seq.), mandates programs to reduce pollution discharges to surface waters. These include, for example, Total Maximum Daily Loads, the National Pollutant Discharge Elimination System, and the Nonpoint Source Program. However, these programs are legally and programmatically disconnected from the NPDWR. While water pollution controls that reduce surface water contamination may make it easier for some public water systems to treat their water and comply with the NPDWR, these controls are not specifically designed for that purpose, and the output of public water systems must comply with the NPDWR regardless of pollution levels in their source waters. To support its regulatory efforts, the EPA conducts health assessments for specific chemical substances. Such an assessment begins with a thorough evaluation of the current scientific literature to characterize the hazard from a particular substance. If supported by the data, a quantitative assessment of cancer and noncancer effects is conducted consistent with Agency risk assessment guidelines. For noncancer health hazards, a series of uncertainty factors is applied to a “No Observed Adverse Effects Level” (NOAEL) or a “Lowest Observed Adverse Effects Level” (LOAEL), as determined in laboratory or population studies of particular health endpoints, to generate a Reference Dose (RfD) for ingestion or a Reference Concentration (RfC) for inhalation. Alternately, more recent assessments may use a benchmark dose approach, which involves fitting mathematical models to dose-response data and using the results to select a benchmark dose that is associated with a predetermined physiological response (7). An RfD or RfC is defined as an estimate of a daily oral or continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. An RfD or RfC, however, is not a bright line between safe and toxic; health risks are not expected to increase appreciably at exposures immediately above the level of an RfD or RfC. For cancer potency, the results of high-dose laboratory experiments or occupational studies are typically extrapolated to the lower levels expected in the environment to generate a dose-response curve. The slope and shape of this curve indicate the relative cancer potency of the substance. Sometimes this curve is also used to compute a Risk Specific Dose (RSD) or Risk Specific Concentration (RSC), which is the dose or concentration required to create a particular risk of cancer, typically in the range 10-4-10-6 cancers per lifetime of exposure. In accordance with agency policy, EPA health assessments undergo peer review. Many EPA health assessments also undergo consensus review by senior staff scientists representing the EPA’s program offices and regions; these assessments are included in the IRIS database. The RfD/RfC and cancer potency values in the IRIS database are not regulations, but they may become the basis for health-based regulatory limits. The EPA reviews its health assessments periodically and, if necessary, revises them to reflect new scientific research.
TABLE 2. Summary of Air Standard Comparisonsa pollutant
EPA less strict
equal
EPA more strict
CO NO2 ozone lead PM10 PM2.5 SO2 total
16 (39%) 16 (84%) 30 (97%) 1 (25%) 25 (64%) 2 (100%) 40 (87%) 130 (71%)
17 (41%) 2 (11%) 1 (3%) 3 (75%) 8 (21%) 0 (0%) 5 (11%) 36 (20%)
8 (20%) 1 (5%) 0 (0%) 0 (0%) 6 (15%) 0 (0%) 1 (2%) 16 (9%)
a
Listed as number of comparisons (percent of comparisons).
Methods and Results Air Standards. The first part of this study compared the U.S. NAAQS with corresponding air quality standards and guidelines from around the world. This began with a thorough search for original government or organizational documents, such as statutes, regulations, or decrees. Much of this information was available on official government Web sites. In general, information was sought from any country with published standards or guidelines, whether enforceable or not. However, information was specifically sought and obtained for the State of California (17 C.C.R. 70200), the World Health Organization (8), and the European Union (911). The search also yielded standards or guidelines from numerous countries, especially industrialized democracies, as well as four Canadian provinces. No country was included or excluded based on the level of its standards or guidelines. Table 1 shows the results of the search, for those pollutants and averaging periods listed in the U.S. NAAQS. Expanded results appear in the Supporting Information (Table S1), including other averaging periods used by some countries for some pollutants, as well as standards for total suspended particulates (TSP), a form of particulate matter which some countries regulate. The EPA discontinued regulation of TSP in 1987 in favor of PM10. Standards for air pollutants whose ambient levels are regulated by countries other than the United States, e.g. benzene or sulfates, are not listed. Standards for longer time periods are lower, to limit cumulative exposure; standards for shorter time periods are higher, to limit exposure from peak pollution episodes. For consistency, all of the standards are listed as concentrations in either milligrams or micrograms per cubic meter, rather than parts-per-million or parts-per-billion, as they are sometimes specified in regulations. In all, 182 direct comparisons are possible. Examination of Table 1 reveals that, for a given pollutant over a given averaging period, EPA-promulgated air standards are less strict than those of other countries in 71% of the comparisons, comparable in 20%, and more strict in 9%. Only for the 8-h carbon monoxide standard are several other countries less strict, and even here many countries have the same standard as the United States. One item of note is U.S. leadership in setting PM2.5 standards. These U.S. PM2.5 standards were among the first in the world; several other countries are now considering setting comparable PM2.5 standards. Table 2 and Figure S1 in the Supporting Information quantitatively summarize the results by pollutant, for all instances where identical averaging times allow direct comparison with the U.S. NAAQS. Water Standards. The next part of this study compared the U.S. NPDWR with corresponding drinking water quality standards and guidelines from around the world. This involved a search similar to that conducted for air quality standards. Again, information was sought from any country with available standards or guidelines, and it was specifically obtained for California (22 C.C.R. 64431 et seq.), the World VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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0.01 0.8 0.05 0.0005 10d e 0.01
0.005 0.05 2 0.07 1.5 0.01 0.001 10d 1d 0.01 0.05
0.2 1.5 0.01 0.001 45 3.2 0.01 0.2 1.5 0.01 0.001 45 3.2 0.01
0.2 1.5 0.01 0.001 45 e 0.01
0.2 1.5 0.01 0.001 10d 1d 0.01
0.2 1.5 0.01 0.001 10d 1d 0.01
0.002 0.05 2 0.08 1.5 0.01 0.001 50 3 0.01 0.005 0.05 0.005 0.05 0.005 0.05 0.005 0.05
0.005 0.05 2 0.05 1.5 0.01 0.001 50 0.5 0.01
0.005 0.05
0.7 1 1 1 1 1
0.005 0.05 2 0.05 1.5 0.01 0.001 50 0.5 0.01 0.005 0.05 2 0.05 1.5 0.01 0.001 50 0.5 0.01 0.003 0.05 2 0.07 1.5 0.01 0.001 50 3 0.01
0.005 0.05 2 0.05 1.5 0.01 0.001 50 0.5 0.01
0.7 0.7
0.005 0.05 2 0.05 1.5 0.01 0.001 50 0.5 0.01
a Final 2005 standard. standard.
0.006 0.01 7b 2 0.004 0.005 0.1 1.3c 0.2 4 0.015c 0.002 10d 1d 0.05 0.002 antimony arsenic asbestos barium beryllium cadmium chromium copper cyanide fluoride lead mercury nitrate nitrite selenium thallium
b
Million fibers per liter (>10 µm). c Action level. Treatment required; exceeding this level requires additional action. d Measured as nitrogen, rather than NO3- or NO2-. e Included in nitrate
0.01
0.01 0.05 1 0.2 0.7 0.05 0.002 45
1
0.7 0.004 0.003 0.05 2 0.08 1.5 0.01 0.002 50 3 0.01 0.7
0.05 0.003 0.01 0.025a 0.01 0.003 0.007 0.006 0.025 0.006 0.025 0.006 0.025 0.006 0.025 0.006 0.025 0.005 0.01 0.005 0.01 0.005 0.01 0.005 0.01 0.005 0.01 0.005 0.01
0.006 0.05 7b 1 0.004 0.005 0.05 1.3c 0.15 2 0.015c 0.002 10d 1d 0.05 0.002
Thailand N.Z. Mexico Japan Australia Quebec Ontario BC Alberta Canada U.K. Germany France Austria EU WHO CA U.S. contaminant [mg/l]
TABLE 3. Water Quality Standard Comparison - Inorganic Chemicals
Health Organization (12), and the European Union (13). Water quality standards proved more difficult to find than air quality standards, but the search revealed standards or guidelines for several countries and four Canadian provinces. Table 3 shows the results of the search for inorganic chemicals, limited to those listed in the U.S. NPDWR. Table S2 in the Supporting Information shows similar results for disinfectants, disinfection byproducts, and organic chemicals. Standards for microorganisms and radionuclides had few direct numerical comparisons and are thus not listed. Secondary standards, i.e., nonenforceable standards affecting the aesthetic qualities of drinking water, are also not listed. Except for asbestos, all of the standards are listed as concentrations in either milligrams per liter (mg/L) or micrograms per liter (µg/L). In all, 562 comparisons are possible. Given the large number and variety of water quality standards, direct comparison is somewhat more complicated than it is for air quality standards. However, examination of Tables 3 and S2 suggests that the U.S. standards tend to be less strict for inorganic chemicals, as noted in 61% of these comparisons; somewhat more strict for disinfectants and disinfection byproducts, as seen in 45% of these comparisons; and more strict about as often as less strict for organic chemicals, comprising 38% and 46%, respectively. Table 4 and Figure S2 in the Supporting Information quantitatively summarize the results for these three broad categories of water standards, excluding European pesticide standards. Health Assessments. As noted previously, many EPA health assessments undergo peer and Agency consensus reviews and are entered into the Integrated Risk Information System (IRIS). In fact, many assessments are conducted specifically for this program. While some program offices within the EPA do not submit their assessments to IRIS, the IRIS database contains the Agency’s consensus positions on the health effects associated with chronic exposure to hundreds of environmental chemicals. The last part of this study examined quantitative health assessments from the IRIS online database (14), in three separate analyses. The first analysis began with a search for all quantitative assessments for noncancer health effects in IRIS, yielding 69 RfC values and 356 RfD values. This was followed by a search for comparable noncancer benchmark values from other agencies. This included Minimal Risk Levels (MRLs) from the Agency for Toxic Substances and Disease Registry’s (ATSDR) toxicological profiles (15), Chronic Reference Exposure Levels (RELs) from the State of California’s Office of Environmental Health Hazard Assessment’s Toxicity Criteria Database (16), Tolerable Concentrations and Tolerable Intakes from Health Canada, as listed in the International Toxicity Estimates for Risk (ITER) online database (17), and Tolerable Concentrations and Tolerable Daily Intakes from The Netherlands’ National Institute of Public Health and the Environment (RIVM (18)). ATSDR, Health Canada, and RIVM list both inhalation and ingestion values, while the California database lists only inhalation RELs. A comparison of these values revealed that 40 chemicals in the IRIS database with inhalation RfCs also have corresponding values established by ATSDR, California, Health Canada, and/or RIVM; 65 specific comparisons between the EPA values and other agencies’ values could be made. Similarly, 73 chemicals in IRIS with oral RfDs also have corresponding values established by ATSDR, Health Canada, and/or RIVM; 101 specific comparisons were possible. Table 5 and the left half of Figure S3 in the Supporting Information summarize the results of these comparisons. In all cases, a lower RfC or RfD value indicates a higher estimate of toxicity (or a greater degree of uncertainty, as reflected in the application of uncertainty factors). Tables S3 and S4 in the Supporting Information display the reference values for
TABLE 4. Summary of Water Standard Comparisonsa pollutant
EPA less strict
equal
EPA more strict
inorganic chemicals 113 (61%) 51 (28%) 21 (11%) disinfectants/byproducts 10 (26%) 11 (29%) 17 (45%) organic chemicals 156 (46%) 55 (16%) 128 (38%) total 279 (50%) 117 (21%) 166 (29%) a
Listed as number of comparisons (percent of comparisons).
TABLE 5. Summary of Health Assessment Comparisonsa value
other agency value lower
equal
EPA value lower
RfC RfD RSC RSD Total
21 (32%) 34 (34%) 25 (41%) 25 (37%) 105 (36%)
12 (18%) 34 (34%) 19 (31%) 21 (31%) 86 (29%)
32 (49%) 33 (33%) 17 (28%) 21 (31%) 103 (35%)
a
Listed as number of comparisons (percent of comparisons).
all 166 comparisons. For inhalation toxicity, the EPA RfC values in IRIS are lower than the reference values developed by other agencies about as often than they are higher or identical. For oral toxicity, the EPA RfD values are higher about as often as they are lower, and they are often the same. The second analysis began with a search for all quantitative cancer assessments in IRIS, finding 58 inhalation unit risks and 86 oral slope factors. These values were converted to RSCs and RSDs at the 10-5 risk level by dividing them into 10-5. This was followed by a search for comparable values from the State of California (16), Health Canada (17), and RIVM (18). The California values required the same conversions as the IRIS values. The Health Canada values were listed as Tumorigenic Concentrations or Doses associated with a 5% increase in the incidence of mortality due to tumors (TC05 or TD05). These values were divided by 5000 to convert them to RSCs and RSDs at the 10-5 risk level. The RIVM values were listed as Cancer Risks at the 10-4 level; these were converted to the 10-5 level for comparison. ATSDR does not conduct quantitative cancer assessments. A comparison of these values found that 49 chemicals in the IRIS database with inhalation unit risks also have inhalation cancer potency values established by California, Health Canada, and/or RIVM; 61 specific comparisons could be made. Similarly, 57 chemicals in IRIS with oral slope factors also have oral cancer
potency values established by California, Health Canada, and/ or RIVM; 67 specific comparisons were possible. Table 5 and the right half of Figure S3 in the Supporting Information summarize the results of these comparisons. A smaller RSC or RSD value indicates a higher estimate of cancer potency. Tables S5 and S6 in the Supporting Information display the reference values for all 128 comparisons. The EPA RSC or RSD values in IRIS are higher (i.e., indicating a lower cancer potency) than the values developed by other agencies somewhat more often than they are lower, but they are often identical. It must be noted that Health Canada’s different methodology for computing cancer potencies allows only an approximate comparison to the EPA and California values. The third analysis involved searching the IRIS database for substances whose RfC or RfD values had been reassessed and possibly revised since May 2000. This yielded 16 reference values for 14 substances where both old and new values were available for comparison. Table 6 shows these results, where a smaller RfC or RfD indicates a higher estimated toxicity (or a greater degree of uncertainty). Of the 16, three reference values decreased, one due to the application of an uncertainty factor that was not originally applied. Six values increased (two by 2 orders of magnitude) as a result of the use of newer toxicity data, the application of smaller uncertainty factors, and the use of a benchmark dose approach rather than the traditional NOAEL/LOAEL approach. Reassessments of the health effects literature for the remaining seven chemicals resulted in no changes in their reference values. Similarly, the IRIS database was also searched for substances whose cancer potency reference values had been reassessed and possibly revised since 1992. This yielded 11 reassessed values for eight substances, as shown in Table 7. In five of the 11 cases, the estimated cancer potency decreased after reassessment, as reflected in lower oral slope factors and inhalation unit risks. These changes were generally within 1 order of magnitude. In two cases, the estimated cancer potency was essentially unchanged after reassessment. For the four remaining estimates of cancer potency, numerical comparisons could not be made. In three instances, it was determined upon reassessment that quantitative doseresponse assessment was not supported, and new estimates of cancer potency were not derived. In the case of the oral slope factor for chloroform, the reassessment used a nonlinear approach; direct comparison with the previous oral slope factor (which assumed a linear dose-response model) was not appropriate.
TABLE 6. Noncancer Health Assessment Changes chemical acetone acrolein chloral hydrate chlorine dioxide chloroform 1,1-dichloroethylene 1,3-dichloropropene 1,3-dichloropropene diesel emissions hexachlorocyclopentadiene hydrogen sulfide methyl ethyl ketone methyl ethyl ketone methylmercury phenol xylenes a
reference valuea oral RfD inhalation RfC oral RfD inhalation RfC oral RfD oral RfD oral RfD inhalation RfC inhalation RfC oral RfD inhalation RfC oral RfD inhalation RfC oral RfD oral RfD oral RfD
old value 10-1 mg/kg-day
1× 2 × 10-5 mg/m3 2 × 10-3 mg/kg-day 2 × 10-4 mg/m3 1 × 10-2 mg/kg-day 9 × 10-3 mg/kg-day 3 × 10-4 mg/kg-day 2 × 10-2 mg/m3 5 × 10-3 mg/m3 7 × 10-3 mg/kg-day 1 × 10-3 mg/m3 6 × 10-1 mg/kg-day 1 × 100 mg/m3 1 × 10-4 mg/kg-day 6 × 10-1 mg/kg-day 2 × 100 mg/kg-day
revised value 9 × 10-1 mg/kg-day 2 × 10-5 mg/m3 1 × 10-1 mg/kg-day 2 × 10-4 mg/m3 1 × 10-2 mg/kg-day 5 × 10-2 mg/kg-day 3 × 10-2 mg/kg-day 2 × 10-2 mg/m3 5 × 10-3 mg/m3 6 × 10-3 mg/kg-day 2 × 10-3 mg/m3 6 × 10-1 mg/kg-day 5 × 100 mg/m3 1 × 10-4 mg/kg-day 3 × 10-1 mg/kg-day 2 × 10-1 mg/kg-day
RfD ) reference dose; RfC ) reference concentration. A smaller value indicates a higher estimated toxicity or a greater degree of uncertainty.
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TABLE 7. Cancer Potency Assessment Changes chemical
reference valuea
old value
revised value
benzene benzene beryllium 1,3-butadiene chlordane chlordane chloroform chromium 1,1-dichloroethylene 1,1-dichloroethylene PCBs
oral SF inhalation UR oral SF inhalation UR oral SF inhalation UR oral SF Inhalation UR oral SF inhalation UR oral SF
2.9 × 10-2 (mg/kg-d)-1 8.3 × 10-6 (µg/m3)-1 4.3 (mg/kg-d)-1 2.8 × 10-4 (µg/m3)-1 1.3 (mg/kg-d)-1 3.7 × 10-4 (µg/m3)-1 6.1 × 10-3 (mg/kg-d)-1 1.2 × 10-2 (µg/m3)-1 6.0 × 10-1 (mg/kg-d)-1 5.0 × 10-5 (µg/m3)-1 7.7 (mg/kg-d)-1
1.5 × 10-2-5.5 × 10-2 (mg/kg-d)-1 2.2 × 10-6 -7.8 × 10-6 (µg/m3)-1 inadequate data to derive SF 3.0 × 10-5 (µg/m3)-1 3.5 × 10-1 (mg/kg-d)-1 1 × 10-4 (µg/m3)-1 RfD ) 0.01 1.2 × 10-2 (µg/m3)-1 equivocal evidence of oral carcinogenicity insufficient weight of evidence to derive UR 0.04-2.0 (mg/kg-d)-1
a
SF ) slope factor; UR ) unit risk. A larger value indicates a higher estimated cancer potency.
The results of this limited sample of health reassessments are not unexpected. Absent any newly discovered toxic or carcinogenic effects, one might expect an objective health reassessment to be more likely to produce a less stringent benchmark value, as new research reduces uncertainty in the assessment and thus reduces the need to use default uncertainty factors.
Discussion To provide a quantitative context for the EPA’s standard setting and health assessment process, this study examined the U.S. national ambient air quality standards, the U.S. national primary drinking water regulations, and a sample of the EPA’s health assessments for chemical substances. The U.S. NAAQS are generally comparable to or less strict than the air quality standards of other countries and international organizations. Comparisons with the U.S. NPDWR are more complicated, but these tend to be less strict than the water quality standards of other countries for inorganic chemicals, somewhat more strict for disinfectants and disinfection byproducts, and more strict about as often as less strict for organic chemicals. Reference values for noncancer effects and cancer potency derived during EPA health assessments (specifically those in the IRIS database) are not preponderantly higher or lower than those of other agencies; they are higher about as often as they are lower, and they are often identical. In the sample examined here, revisions based on new science more often than not resulted in a less stringent noncancer reference value or cancer potency benchmark. Of course, there are several important caveats in an analysis as broad as this one. Perhaps the most important caveat involves implementation and enforcement. Air quality standards are set at levels intended to protect public health and welfare, but they accomplish little unless they are translated into enforceable regulations that actually improve and maintain air quality. Such regulations vary widely from country to country. For the United States, the CAA contains detailed requirements for NAAQS implementation (42 U.S.C. 7410) and enforcement (42 U.S.C. 7413) (see also 42 U.S.C. 7470-7479 and 7501-7515). These are designed to ensure that areas attain the NAAQS in a timely fashion. The enforcement provisions allow the EPA to issue administrative orders, assess administrative penalties, undertake civil action, and even initiate criminal prosecution for violations. The EPA has taken numerous violators to court, often in conjunction with the Department of Justice, to enforce compliance with the CAA and with the EPA regulations derived from it. The CAA also contains provisions for nationwide pollution control measures, which the EPA has implemented, for example, in the form of vehicle emission standards, interstate pollutant transport rules, and the market-based Acid Rain Program. The net effect has been a 3462
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substantial improvement in U.S. air quality (19). For other countries, however, implementation, enforcement, and the effects of standards on actual air quality vary widely. Many countries have adopted the World Health Organization’s guidelines for air quality (8), but these guidelines have no inherent legal authority, and individual countries choose the extent to which they implement and enforce them. Likewise, the European Union depends on the governments of member states to implement and enforce its air quality limit values (9-11) via national regulations (e.g., refs 20-22), and Canada depends on its provinces to enact enforceable standards, which may differ from the federal standards. Some U.S. states, such as California, have their own air quality standards, although these cannot be less strict than the NAAQS. Some developed countries have achieved considerable improvements in air quality, but the approaches used are often too resource-intensive for poorer countries (8). Air quality has deteriorated in many Asian and Pacific countries with air quality standards because of weak enforcement, although some countries are making progress (23). In some developing countries with air quality standards, there are no enforcement mechanisms; in others, industries are allowed to pollute for economic reasons (24). Likewise, drinking water standards also require regulations to implement and enforce them, and these also vary from country to country. However, unlike ambient air quality standards, which require action by a diverse array of pollutant sources, drinking water standards focus on public water systems. In the United States, these systems vary dramatically in scale but are all responsible for providing customers with safe drinking water. The EPA works closely with public water systems to ensure they meet the NPDWR, offering training and technical assistance. The EPA regularly surveys the infrastructure needs of the nation’s public water systems (25) and provides financial assistance for improvements. The SDWA provides detailed requirements for enforcing the NPDWR (42 U.S.C. 300g-2 and 3), emphasizing state responsibility. The EPA is authorized to issue administrative orders, initiate civil action, levy substantial penalties, and even file criminal charges for violations of the NPDWR. The EPA collects reports from the states and compiles an annual compliance report. The report for 2000, for example, shows that 94% of the nation’s public water systems did not violate any health-based standards in 2000 (26). Other countries methods and results vary, however. As with air standards, many countries have adopted some of the World Health Organization’s guidelines for drinking water quality (12), which require national laws or regulations to give them authority or enforceability. The European Union has required its members to implement and enforce its 1998 drinking water standards (13), superseding the 1980 standards (27); national regulations promulgating these standards have begun to take effect (e.g., refs 28-30). Enforcement of the
1980 standards has been active, although compliance problems exist; a disparity of reporting data among countries makes the comparison of enforcement effectiveness difficult (31). In England and Wales, for example, where the Drinking Water Inspectorate is empowered to conduct technical inspections, require facility improvements, and even prosecute violators if necessary, annual reports have shown good compliance (32). Elsewhere, Australia’s guidelines (33) and New Zealand’s standards (34) do not set legal limits but rather define acceptable water quality and recommend appropriate actions for states and communities. Canada’s guidelines (35) are designed to apply to all drinking water systems but are not legally enforceable; water is a provincial responsibility, and several provinces have enacted the guidelines. There are also a number of other caveats and general observations regarding air and water standards. Officially sanctioned measurement methods may differ from country to country, which may increase or decrease the effective level of a standard. Regulations vary in their forms, such as the averaging period or the number of times a standard can be exceeded without violating it. In a few cases, e.g., nitrate and nitrite, countries measure different chemical species and thus have different standards. In some cases, the United States has promulgated one standard for a family of chemicals, e.g., trihalomethanes, while other countries have standards for each chemical. In other cases, e.g., heptachlor and heptachlor epoxide, the opposite is true. The EU pesticide standard uniformly limits all pesticides in a water sample to 0.1 µg/L individually and 0.5 µg/L collectively (13), which is often much less than other countries’ standards for specific pesticides. Conversely, Australia’s drinking water guidelines specify values for a great many individual pesticides (33). Finally, while this analysis strove for a representative sample, it is not truly comprehensive, in that it does not include air quality standards from every country, organization, state, and province that has them. Science is expected to be a major factor in many EPA decisions, especially those described here. Both external mandates (e.g., the Clean Air Act) and internal guidance (e.g., refs 36 and 37) require the EPA to thoroughly evaluate the best available research in order to understand health risks and to set protective, justifiable standards. The technical underpinnings of the rulemaking and assessment processes typically include comprehensive peer review (38). The NAAQS process includes close consultation with external experts on the Clean Air Scientific Advisory Committee (42 U.S.C. 7409(d)(2)), and the NPDWR process includes collaboration with the National Drinking Water Advisory Council (42 U.S.C. 300g-1(d)), the agency’s Science Advisory Board (42 U.S.C. 300g-1(e)), and committees formed under the Federal Advisory Committee Act (5 U.S.C. App.). Further, there are ample opportunities for public comment on proposed standards. Standards and health assessments are reviewed periodically in light of advancing research, and standards are revised as necessary to properly protect public health. Of course, science is not the only factor in setting policy. While some parts of the law require a degree of caution or an “adequate margin of safety” (e.g., 42 U.S.C. 7409(b)(1) for NAAQS), which can make a standard more strict, other parts require consideration of technical feasibility and cost (e.g., 42 U.S.C. 300g-1(b) for NPDWR), which can make a standard less strict. Recent standards have undergone cost-benefit analyses, which have shown generally favorable results. See the Supporting Information for more discussion. The results of this study suggest that the EPA’s standards and health assessments are not out of line with those of other agencies and other countries. In the future, it would be instructive to compare not only standards but also ambient air pollution levels and drinking water contaminant levels among the countries with published standards. This would
allow comparison of the effectiveness of the standards in addition to their nominal limit values.
Acknowledgments Thanks to Robert Fegley and Monica Alvarez for their initial examination of the health benchmarks; Kevin Teichman and Robert Dyer for their guidance and helpful comments; Susan Rieth and Amy Mills for historical benchmark values and helpful comments; William Farland, David McKee, and Rita Schoeny for helpful internal review; and Paul Gilman for setting this project in motion.
Supporting Information Available Full data for air quality standards; data for water quality standards related to disinfectants, disinfection byproducts, and organic chemicals; data for noncancer health assessments; data for cancer potency assessments; summary figures for air standard, water standard, and health assessment comparisons; and an additional discussion on cost-benefit analysis. This material is available free of charge via the Internet at http://pubs.acs.org.
Literature Cited (1) U.S. Environmental Protection Agency. 2003-2008 EPA Strategic Plan: Direction for the Future; EPA-190-R-03-003; 2003. (2) U.S. Environmental Protection Agency. Air Quality Criteria for Particulate Matter; EPA-600-P-99-002aD; 2003. (3) U.S. Environmental Protection Agency. Air Quality Criteria for Ozone and Related Photochemical Oxidants; EPA-600-P-93004aF; 1996. (4) U.S. Environmental Protection Agency. Review of the National Ambient Air Quality Standards for Particulate Matter, Policy Assessment of Scientific and Technical Information, OAQPS Staff Paper; EPA-452-D-03-001; 2003. (5) U.S. Environmental Protection Agency. Review of National Ambient Air Quality Standards for Ozone, Assessment of Scientific and Technical Information, OAQPS Staff Paper; EPA-452-R-96007; 1996. (6) U.S. Supreme Court. Whitman v. American Trucking Assns., Inc., 531 U.S. 457, 2001. (7) U.S. Environmental Protection Agency. The Use of the Benchmark Dose Approach in Health Risk Assessment; EPA-630-R-94-007; 1995. (8) World Health Organization. Guidelines for Air Quality; WHO/ SDE/OEH/00.02, 2000. (9) European Union. Council Directive 1999/30/EC, 1999. (10) European Union. Council Directive 2000/69/EC, 2000. (11) European Union. Council Directive 2002/3/EC, 2002. (12) World Health Organization. Guidelines for Drinking Water Quality; 1996. (13) European Union. Council Directive 1998/83/EC, 1998. (14) U.S. Environmental Protection Agency. Integrated Risk Information System; 2004. Available at http://www.epa.gov/iriswebp/ iris/index.html. (15) Agency for Toxic Substances and Disease Registry. Toxicological Profiles; 2004. Available at http://www.atsdr.cdc.gov. (16) California Office of Environmental Health Hazard Assessment. Toxicity Criteria Database; 2004. Available at http:// www.oehha.ca.gov/risk/ChemicalDB/. (17) Toxicology Excellence for Risk Assessment and Concurrent Technologies Corporation. International Toxicity Estimates for Risk; 2004. Available at http://www.tera.org/iter/. (18) National Institute of Public Health and the Environment, Netherlands. Reevaluation of Human-Toxicological Maximum Permissible Risk Levels; RIVM report 711701 025; 2001. (19) U.S. Environmental Protection Agency. Latest Findings on National Air Quality: 2002 Status and Trends; EPA-454-K-03001; 2003. (20) U.K. Statutory Instrument 2001 No. 2315. The Air Quality Limit Values Regulations 2001; 2001 (as amended). (21) French Decree No. 98-360. Related to Monitoring of Air Quality and Its Effects on Health and on the Environment, to Air Quality Objectives, to Alarm Thresholds, and to Limit Values; 1998 (as amended). (22) German Ordinance BImSchV 22 2002. Ordinance to Implement the Federal Immission Control Law; 2002. VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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(23) Economic and Social Commission for Asia and the Pacific and Asian Development Bank. State of the Environment in Asia and the Pacific 2000; United Nations, 2000. (24) Haron, A. H.; Innes, J. L. Conclusions. In Air Pollution and the Forests of Developing and Rapidly Industrializing Regions; Innes, J. L., Haron, A. H., Eds.; CAB International: 2000. (25) U.S. Environmental Protection Agency. Drinking Water Infrastructure Needs Survey: Second Report to Congress; EPA-816R-01-004; 2001. (26) U.S. Environmental Protection Agency. Providing Safe Drinking Water in America: 2000 National Public Water Systems Compliance Report; EPA-305-R-02-001; 2002. (27) European Union. Council Directive 80/778/EEC, 1980. (28) U.K. Statutory Instrument 2000 No. 3184. The Water Supply (Water Quality) Regulations 2000; 2000. (29) French Decree No. 2001-1220. Related to Water Destined for Human Consumption, Excluding Natural Mineral Water; 2001. (30) German Ordinance TrinkwV 2001. Ordinance to Amend the Drinking Water Ordinance; 2001. (31) U.K. Drinking Water Inspectorate. Investigation of Drinking Water Quality Enforcement Procedures in Member States of the European Union; DWI0800, 1998.
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(32) U.K. Drinking Water Inspectorate. Drinking Water 2002: Annual Report; 2003. (33) National Health and Medical Research Council and Agriculture and Resource Management Council. Australian Drinking Water Guidelines; 1996. (34) New Zealand Ministry of Health. Drinking-Water Standards for New Zealand 2000; 2000. (35) Health Canada. Guidelines for Canadian Drinking Water Quality; H48-10/1996E (and revisions); 1996. (36) U.S. Environmental Protection Agency. Guidelines for Carcinogen Risk Assessment; NCEA-F-0644; 1999. (37) U.S. Environmental Protection Agency. Risk Characterization Handbook; EPA-100-B-00-002; 2000. (38) U.S. Environmental Protection Agency. Peer Review Handbook; EPA 100-B-00-001; 2000.
Received for review October 10, 2003. Revised manuscript received March 23, 2004. Accepted March 26, 2004. ES035132H
