PESTICIDES IN SURFACE WATERS: Distribution, Trends, and Governing Factors - Chapter 6 pdf

Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters a N P [All standards and criteria values are from Nowell and Resek

APTER 6

Analysis of Key Topics-Environmental Significance

Under provisions of the Safe Drinking Water Act (SDWA), the U.S Environmental Protection Agency (USEPA) has established an enforceable maximum contaminant level (MCL) allowed in drinking water for certain pesticides with past or present use in the United States (Table 6.1) The MCLs are health-based standards and are results of chronic toxicity tests conducted with animals The MCLs are derived from the highest concentration at which no adverse health effects were observed in the test animals, multiplied by a safety factor of 100, or 1,000 in the case of suspected or probable carcinogens Considerations of treatment feasibility, cost of treatment, and analytical detection limits also were included in the derivation of the MCLs The USEPA also has established a maximum contaminant level goal (MCLG) for all chemicals with an established MCL The MCLG is a nonenforceable concentration of a drinking-water contaminant that is protective of human health and allows an adequate margin of safety (Nowell and Resek, 1994), without regard for economic or analytical constraints The MCLG is set at zero for known or probable human carcinogens Pesticides with an MCLG of zero include alachlor, chlordane, dibromochloropropane (DBCP), EDB, heptachlor, heptachlor epoxide, pentachloro- phenol (PCP), hexachlorobenzene (HCB), and toxaphene Of these, alachlor is the only one with significant current use in the United States These standards apply to finished (treated) drinking water supplied by a community water supply, and require that the annual average concentration

of the specific contaminant be below the MCL As of 1994, the SDWA requires most suppliers of drinking water to monitor for 39 pesticides or pesticide transformation products in finished water,

14 of which are no longer registered for use in the United States Pesticides with current agricultural use, for which MCLs have been established and monitoring is required, include seven

herbicides (alachlor, atrazine, 2,4-D, diquat, glyphosate, picloram, and simazine), four

insecticides (carbofuran, lindane, methoxychlor, and oxamyl), and one fungicide (PCP) In addition, monitoring is required for 13 pesticide-related compounds for which MCLs have not been established (U.S Environmental Protection Agency, 1994b) From a compliance standpoint, the standards (MCLs) do not apply to most water bodies reported on in this book, since most of the studies reviewed were not analyzing finished drinking water

For many of the pesticides with no established MCL, other (nonregulatory) criteria have been established The USEPA has issued drinking-water health advisory (HA) levels for adults and children for various exposure periods The National Academy of Sciences has issued a Suggested No-Adverse-Response Level (SNARL) for many pesticides Both the HA and SNARL values represent estimates of the maximum level of a contaminant in drinking water at which no

Table 6.1 Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters a N

P

[All standards and criteria values are from Nowell and Resek (1994) Concentrations are in microgram(s) per liter Human Health: MCL, Maximum

contaminant level for drinking water established by the U.S Environmental Protection Agency (USEPA); MCLG, Maximum contaminant level goal for - drinking water established by the USEPA (equal to zero for known or probable human carcinogens); HA (child, long term), Health advisory level for drinking

water established by the USEPA (for a 10-kilogram child over a 7-year exposure period and for a 70-kilogram individual over a 70-year exposure period) 2

SNARL, Suggested No-Adverse-Response Level for drinking water established by the National Academy of Sciences (NAS) Exceeded Values, Number of - studies in which a criteria value was exceeded / Number of studies in which an analyte was targeted All studies from Tables 2.1 and 2.2 that targeted the #

compound are included in the denominator, regardless of whether a maximum concentration was reported The number of studies with exceeded values may be V,

an underestimate, because some studies did not report a maximum concentration Aquatic Organism Health: USEPA, Acute and Chronic, Established 2

concentration below which adverse effects on aquatic organisms are not expected for acute or chronic exposure National Academy of Sciences and the

National Academy of Engineering (NASDJAE), Concentration established in 1973 below which adverse effects are not expected Exceeded Values, as defined

USEPA

nsg

2 0.2

Exceeded

nsg

0 nsg nsg MCLG

nsg

2 0.2

0.3 0.5 nsg 0.5

HA

nsg 4.5

33

Exceeded values

nsg nsg nsg nsg

Studies in which MCL or

nsg 1.6

2

3

values rn

nsg nsg nsg nsg

nsg nsg nsg

2/57 2/50

nsg 4/72

I

nsg

0160 6/65

Bradshaw and others, 1972 Page, 1981

Warry and Chan, 1981 Kuntz and Warry, 1983

Klaasen and Kadoum, 1975 Wany and Chan, 1981 Leung and others, 1982 Kuntz and Warrv 1983 None

None Nicholson and others, 1964 Bradshaw and others, 1972 Page, 198 1

Warry and Chan, 1981 Kuntz and Warry, 1983 Takita, 1984

3 2.4 1.1 2.5

0.22 0.19

2

nsg 0.0043 0.001 0.0019

0.056 0.0023 0.08

0.01 nsg nsg nsg

13/57 17/50 38/74 37/72

nsg nsg nsg

4/45 16/60 14/65

Table 6.1 Standards and criteria for orotection of human and aauatic oraanism health for ~esticides targeted in surface waters Continued

HA exceeded

Table 6.1 Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters Continued Q)

Aquatic Organism Health

Yorke and others, 1985 Wnuk and others, 1987 Baker, 1985, 1988b Squillace and Engberg, 1988 Moyer and Cross, 1990

Table 6.1 Standards and criteria for protection of human and aauatic oraanism health for pesticides taraeted in surface waters Continued

Ametryn

Atratone

Atrazine

MCL nsg nsg

3 1 ~

Acute nsg nsg nsg

i?

3

8

nsg nsg

Exceeded values 1/11 nsg 21/41

nr

2

9

Chronic nsg nsg nsg

HA

nsg nsg

nsg nsg

150

Child

900 nsg

50

Adult

60 nsg

3

100

500

Exceeded values

0111 nsg 16/41

Studies in which MCL or

HA exceeded None

None

Wu and others, 1980 Fishel, 1984 Baker, 1985, 1988b Ward, 1987 Wnuk and others, 1987 Fujii, 1988

Squillace and Engberg, 1988 Moyer and Cross, 1990 Lewis and others, 1992 Thurman and others, 1992 Goolsby and Battaglin, 1993 Goolsby and others, 1993 Pereira and Hostettler, 1993 Squillace and others, 1993

nsg nsg

nsi3 nsg

nsg 2

Table 6.1 Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters Continued IU 0-1

, nsg

USEPA

nsg nsg nsg

nsg nsg nsg nsg

NASfNAE

10

nsg nsg

Acute nsg

nsg nsg nsg

nsg nsg nsg

, nsg

Chronic nsg

nsg nsg

300

nsg nsg nsg nsg

nsg

011

nsg nsg

On

nsg nsg nsg

HA

None None None

SNARL

1,505

nsg nsg

n s g ,

Child

50

nsg nsg , nsg

nsg nsg nsg

Adult

4

nsg nsg , nsg ,

nsg nsg nsg

Exceeded values

3/18

nsg nsg nsg

nsg nsg

Studies in which MCL or

HA exceeded Ward, 1987

Baker, 1988b

Thurman and others, 1992

None None

nsg nsg nsg

nsg nsg nsg

nsg nsg

700

None None None

nsg

011

nsg nsg

nsg nsg nsg

nsg nsg nsg

None None None None

nsg nsg nsg

nsg nsg nsg nsg

325

nsg

200

nsg nsg nsg nsi2

011

nsg

0 n

nsg nsg nsg nsg

nsg nsg nsg nsg

Table 6.1 Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters-Continued

Table 6.1 Standards and criteria for protection of human and aquatic organism health for pesticides targeted in surface waters Continued rv -J

'DDT totals include five studies in which only "total DDT' (sum of DDT, DDD, and DDE) was reported

2~~~ data includes studies in which any of four isomers (a, f3.6, and y [lindane]) were targeted MCL established for lindane only

3~ecornmended maximum concentration in marine waters (no freshwater value established)

40ther insecticides category includes compounds used as acaricides, miticides, and nematocides, as well as insecticides

Analysis of Key Topics-Environmental Significance 271

manner, so that a lifetime HA value for one compound can be compared with a SNARL value

for another A complete description of the derivation and use of the MCL, HA, and SNARL values can be found in Nowell and Resek (1994) Values of these criteria for the pesticides observed in the reviewed studies are shown in Table 6.1 In some cases, there are large differences between the different criteria values for a particular pesticide Nowell and Resek (1994) have recommended that, for sources of drinking water, the MCL, if available, should be used for comparison of observed concentrations with criteria values If no MCL has been established, the HA should be used If neither MCL nor an HA has been established, the SNARL should be used

While the MCL, HA, and SNARL values do not directly pertain to ambient concentrations of pesticides in surface waters, they do provide values with which the observed levels can be compared Since these values are based on the toxicity of the compounds, they can give some idea of the potential significance of the levels observed in surface waters Pesticides that exceeded a criteria value in at least one of the reviewed studies (Tables 2.1 and 2.2) are noted

in Table 6.1 Some compounds with established criteria have not been included in any of the reviewed studies, or have been targeted very infrequently Five pesticides with established MCLs dalapon, dibromochloropropane (DBCP), endothall, ethylene dibromide (EDB), and glyphosate-were not included in any of the reviewed studies listed in Tables 2.1 and 2.2 Of these five, only glyphosate (Figure 3.12) and endothall are currently used in United States agriculture Several important qualifications should be mentioned regarding the data in Table 6.1 First, many of the studies reviewed did not give information on the maximum concentration detected for each analyte Thus, the number of studies in which criteria values were exceeded may actually be higher than is shown in Table 6.1 Second, studies listed in Table 6.1 cover 1958

to 1993, so that the data do not necessarily reflect the current situation Finally, in the table, a reported concentration higher than a criteria value in a single sample in one study is counted the same as many samples with concentrations above criteria values in another study Despite these limitations, several important points are evident

1 Relatively few of the pesticides targeted in the reviewed studies were detected at a level exceeding a drinking water criteria value Of the 52 pesticides or transformation products with an established criterion, 15 were detected at a concentration exceeding

it in at least one sample Eight of these were organochlorine compounds or degradation products detected in studies primarily from the 1970's

2 In recent years, the pesticides most often detected at levels exceeding criteria values have been the triazine and acetanilide herbicides atrazine, alachlor, cyanazine, and simazine The large number of studies in which these compounds exceeded criteria values is, in part, due to more intensive sampling of midwestem surface waters in recent years In several of the studies in which criteria values were exceeded, rivers were sampled frequently during the spring runoff, increasing the likelihood of sampling during peak herbicide concentrations As discussed in Section 5.1, the increased use of these compounds, coupled with their relatively high potential for transport in runoff, results in elevated concentrations in surface waters of the Midwest

in spring and early summer Peak concentrations of these compounds can exceed criteria values, especially in the smaller rivers

3 Herbicides other than the triazines and acetanilides, including the high-use compounds 2,4-D, dicamba, butylate, and trifluralin, were never detected in surface waters at levels exceeding criteria values in the reviewed studies

4 Insecticides commonly used in recent years rarely reach levels in surface waters that exceed drinking-water criteria concentrations

272 PESTICIDES IN SURFACE WATERS

Atrazine concentrations exceeded an established criteria value most often in the reviewed studies, and can be used to more fully explain the human health implications of the levels of pesticides detected in surface waters As discussed earlier, atrazine concentrations have

a seasonal pattern in many rivers throughout the central United States (Figures 3.46,5.2, and 5.7)

In some of these rivers, the MCL of 3 mg/L is exceeded for days to weeks Peak concentrations generally are higher in smaller rivers, but the duration of elevated concentrations often is longer

in larger rivers (Goolsby and Battaglin, 1993) Drinking water for millions of people is obtained from surface water sources in the central United States Community water supplies drawing water from the three major rivers in this region-the Mississippi, Ohio, and Missouri Rivers- serve approximately 10.5 million people (Ciba-Geigy, 1992d) Smaller rivers and reservoirs provide drinking water to approximately 4.3 million people in Ohio, Illinois, and Iowa (Ciba-Geigy, 1992d), and the situation is similar in other states of the region

A series of exposure assessments has been done for populations served by these various water sources (Ciba-Geigy, 1993a,b, 1994b; Richards and others, 1995) In these assessments, annual average concentrations of atrazine were estimated for water bodies used as sources of drinking water, using existing monitoring data from Ciba-Geigy, Monsanto, U.S Geological Survey (USGS), water utilities, and other sources The number of people exposed to various levels of atrazine in drinking water then was calculated and expressed as a percentage of the total population covered in each of the different assessments The results of these assessments indicate that the vast majority of people whose drinking water is derived from surface water in the central United States are exposed to annual average atrazine concentrations well below the MCL In the assessment covering the Mississippi, Missouri, and Ohio Rivers, 85 percent of the population whose drinking water is derived from these rivers was exposed to average concentrations between one-tenth and one-third of the MCL, and approximately 40 percent were exposed to average concentrations slightly over one-third of the MCL No segment of the assessed population was exposed to average atrazine concentrations above the MCL In the assessment for Iowa, 97.8 percent of the assessed population using drinking water derived from surface waters was exposed to average atrazine concentrations of less than one-third of the MCL One lake included in the assessment had an annual average atrazine concentration of over 6 pg/L-more than twice the MCL This reservoir supplies drinking water to approximately 0.7 percent of the assessed population using surface water sources Results were similar in the assessments for Ohio and Illinois In Ohio, no surface water source had an annual average concentration over the MCL, and sources for approximately 8 percent of the assessed population relying on surface water had annual concentrations of slightly over 2 pg/L, or two-thirds of the MCL In Illinois, no surface water source had an annual average concentration over the MCL, and sources for approximately 4 percent of the assessed population relying on surface water had annual concentrations over 1 pg/L In both Ohio and Illinois, a large portion of the drinking water derived from surface water comes from the Great Lakes, where atrazine concentrations are quite low In Illinois, Lake Michigan accounts for nearly 80 percent of the drinking water derived from surface waters; in Ohio, Lake Erie accounts for about 42 percent Annual mean atrazine concentrations used in the assessments for Lakes Michigan and Erie were 0.1 and 0.07 yg/L, respectively The results from these assessments probably can be extrapolated to much of the Midwest Illinois, Iowa, and Ohio ranked first, fourth, and sixth among states, respectively, in atrazine use in the late 1980's, the period in which much of the data for these assessments was collected The Mississippi, Ohio, and Missouri Rivers drain much of the area of heaviest atrazine use in the United States (Figure 3.7)

Similar results also would be expected for several other herbicides with established criteria values used in the Mississippi River Basin, based on the results of recent studies of rivers