Exposure to the Herbicides Atrazine and Simazine ... - ACS Publications

Chapter 21

Exposure to the Herbicides Atrazine and Simazine

Downloaded by NORTH CAROLINA STATE UNIV on September 30, 2012 | http://pubs.acs.org Publication Date: May 14, 1998 | doi: 10.1021/bk-1998-0683.ch021

in Drinking Water

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D. P. Tierney, J. R. Clarkson, B.R. Christensen, K.A. Golden, and N. A. Hines 3

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Novartis Crop Protection, Inc., P.O. Box 18300, Greensboro, NC 27419 Montgomery Watson, 365 Lennon Lane, Walnut Creek, CA 94598 Montgomery Watson, 545 Indian Mound, Wayzata, MN 55391 2

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A population-linked database was used to assess exposure to the herbicides atrazine and simazine in drinking water provided by community water systems (CWS) in 21 major use states. Herbicide concentration and populationdatafrom1993 through 1995 were paired for each CWS and aggregated for all CWS to construct state and multi-state exposure profiles. The assessed populations were 110 million for atrazine and 107 million for simazine. The majority of the CWS population had no detectable exposure to atrazine and simazine. All simazine and 99.9% of atrazine populations had exposure below their respective drinking water MCLs. Thirteen of 13,688 CWS had atrazine multi-year mean concentrations above the MCL ranging from 3.06 to 6.19 ppb. Exposures to atrazine and simazine both corresponded to a margin of safety of at least 10,000 for 94% and 96% of the assessed population. Ciba Crop Protection (Ciba) is continuing this monitoring program at least through 1997 to provide a 5-year database, and will update this assessment with 1996 and 1997 data. Atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) and simazine (2chloro-4,6,bis(ethylamino)-5-triazine) are triazine herbicides (1). Both exhibit herbicidal activity on certain annual broadleaf and grass weeds through inhibition of photosynthesis. In the United States, annual atrazine use is the greatest on corn (83%) followed by sorghum (11%) and sugarcane (4%). Atrazine and simazine annual use in the 21 major use states (Figure 1) account for 92% and 91% of the U.S. use, respectively (2). Simazine is used less extensively than atrazine on corn. 252

©1998 American Chemical Society In Triazine Herbicides: Risk Assessment; Ballantine, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.


253 The major uses of simazine are on fruit (especially citrus), nuts, and corn crops. In contrast to atrazine, the greatest use of simazine occurs in Florida and California rather than in the midwestem com states. Atrazine has been detected in surface water and groundwater in several of the major use states (3-7). Typically, groundwater detections of atrazine occur much less frequendy than surface water detections. Also, groundwater detections are usually lower in concentration than that in surface water. In surface water, atrazine concentrations in streams and rivers are episodic, with major peaks in the spring and early summer after field application in April and May. In impounded water bodies (reservoirs), the peak concentrations are usually lower than in rivers and occur at the same time; however, the duration may be longer due to longer hydraulic residence time. Simazine is detected less frequendy than atrazine in ground and surface water in the U.S. and at lower concentrations (3-7). Historically, there have been few studies designed to assess exposure to pesticides through drinking water. The Environmental Protection Agency (EPA) conducted a national survey of rural individual and community water systems (CWS) wells for over 100 pesticides, including atrazine and simazine, in the late 1980s (8). This survey included only groundwater sources. Iowa (9,10), Minnesota (77), and Wisconsin (72) conducted private well and CWS pesticide surveys of drinking water in the late 1980s and early 1990s. Again, auazine and simazine were included. The primary focus was groundwater and the studies were usually limited to only one year of data. A linkage of population to exposure was not made in these studies. This study expands on these past assessments of atrazine and simazine in drinking water using monitoring data collected for a more recent time period (January 1993-December 1995) from CWS in 21 states. Herbicide exposure and population data from 1993 through 1995 are reported here, although Ciba is continuing this monitoring program at least through 1997 (5-year database). This study provides a more complete assessment of the herbicides' frequency of occurrence and concentrations for CWS populations on both ground and surface water sources through the development of a population-linked exposure (PLEX) database. These results add substantially to the body of knowledge on drinking water exposure to these herbicides and evaluate exposure relative to the established federal drinking water standards. E P A Drinking Water Standards The presence of atrazine and simazine in ground and surface raw water sources raised questions regarding possible exposure through drinking water. To provide guidance, EPA developed drinking water health advisory levels (HALs) for both chemicals in 1988 (13). By 1993, EPA, through the Safe Drinking Water Act (SDWA), also established maximum contaminant level (MCL) and monitoring requirements for several pesticides, including atrazine and simazine (14). The recommended HALs and enforceable MCLs are permissible concentrations in drinking water at which adverse health effects would not be expected to occur for the specified exposure duration. Both HALs and MCLs are based on the no

In Triazine Herbicides: Risk Assessment; Ballantine, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.


254 observable effect level (NOEL) in animal toxicity studies. HALs are defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to a certain number of consecutive days of exposure or a certain number of years of exposure, calculated with a margin of safety (Table I). Beginning in 1993, CWS, initiated compliance monitoring of finished water for atrazine and simazine on a quarterly schedule for surface water supplies and once or twice annually for groundwater supplies. The purpose was to assess atrazine and simazine annual running mean concentration for each CWS for compliance with their respective M C L (Table I). METHODS Herbicide Major Use States A hierarchical protocol was developed to determine the segments of the U.S. population served by CWS with potential exposure to atrazine and/or simazine. Based on agricultural land use data (2), company product use data (15,16), and summary national herbicide survey information (17), the 21 major use states were seieciec ίοτ quantitative exposure assessment (Figure 1). These 21 states represent 68% (175 million) of the total U.S. population (18) and 92% and 91% of the annual atrazine and simazine use in pounds, respectively, in the U.S. in 198889 (15,16). The highest atrazine use states are Illinois, Iowa, Nebraska, Indiana, Kansas, Ohio, and Wisconsin. The highest simazine-use states are California and Florida. Population-Linked Exposure (PLEX) Database Drinking water is provided to nearly 243 million people, or 94% of the total U.S. population, by 58,000 CWS (79). The other 15 million people (6%) receive drinking water from private wells or other nonregulated systems (79). A CWS, as regulated under the SDWA, is defined as a facility which provides piped water for human consumption to at least 15 service connections and provides water to the same population year round. A CWS can use different raw water sources: groundwater, surface water (rivers, lakes, and reservoirs) or blends of both. There are 34,591 CWS in the 21 major use states. These facilities provide drinking water to 92% (161 million) of the 175 million people in these states (Table II). SDWA quarterly compliance monitoring data for atrazine and simazine from CWS in the 21 major use states were obtained from the state regulatory agencies. These primary data represent a 3-year period (January 1993-December 1995). In addition, data from monitoring studies (secondary data) for the Great Lakes were used to supplement SDWA data (20). There are 14,440 CWS (42%) with 58,177 quarterly samples analyzed for atrazine entered into the P L E X database (Table III) and 13,853 CWS (40%) with 53,791 simazine data points (Table IV).



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Figure 1. Major Use States for Atrazine and Simazine

Table I. Health Advisory Levels (HALs) and Maximum Contaminant Levels (MCLs) for Atrazine and Simazine Simazine Atrazine HAL MCL HAL Safety MCL Safety Exposure Duration (PPb) (PPb) Factor (PPb) (PPb) Factor 1-day, child: 5 consecutive days 70 100 100 100 10-day, child: 14 consecutive days 70 100 100 100 7-year, child: Approx. 7 years 70 100 50 100 7-year, adult: Approx. 7 years 70 100 200 100 70-year, adult: 4 Lifetime 4 1000 3 3 1000



499 3 23 11 462 87 83 274 328 58 54 279 38 96 8 656 292 294 309 923 38

4,815

Total 174,630,000

Indicates no data

78,027,643

9,741,226 265,800 1,300,000 26,006 6,780,297 1,143,586 567,032 756,983 3,248,001 1,899,245 3,670,671 5,051,393 1,303,428 3,737,841 10,979 11,301,181 3,415,464 6,434,680 5,896,236 10,019,022 1,458,572

Surface Water CWS Total Number Population

31,211,000 700,000 13,679,000 1,172,000 11,697,000 5,713,000 2,814,000 2,531,000 3,789,000 4,295,000 4,965,000 9,478,000 4,517,000 5,234,000 1,607,000 18,031,000 6,945,000 11,091,000 12,048,000 18,031,000 5,082,000

California Delaware Florida Hawaii Illinois Indiana Iowa Kansas Kentucky Louisiana Maryland Michigan Minnesota Missouri Nebraska New York North Carolina Ohio Pennsylvania Texas Wisconsin

State

State Population

347,585 1,483,448 2,102,025 1,346,253 1,710,906 987,724 1,582,365 17,356,621 161,471,531 34,591

13,173,387 70,270,501

28,501

1,275

697,998 2,470,386 1,096,936

789,247 1,785,134 503,494 298,189 34,605

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-

120,326

34,161,675 579,674 14,290,000 1,340,410 10,907,753 3,927,866 2,310,506 2,232,811 3,754,395 4,556,695 4,267,002 7,007,614 3,420,064 5,440,372 1,259,415 16,547,552 4,842,975 9,744,747 10,337,094 17,043,276 3,499,635 3,718 241 2,181 138 2,165 924 1,156 920 518 1,404 513 1,620 957 1,188 676 3,202 2,683 1,540 2,303 5,331 1,213

1,865,294 171,800 690,000 28,644 1,651,351 1,022,093 392,528 743,962 133,780 0 70,000 214,753 0 270,354 389,261 743,725 103,291 0 2,917,688 1,626,417 138,446 60 1 124 5 367 33 37 32 18 0 6 12 0 10 3 275 5 0 214 70 3 22,555,155 142,074 12,300,000 1,285,760 2,476,105 1,762,187 1,350,946 731,866 372,614 2,657,450 526,331 1,741,468 2,116,636 1,432,177 859,175 4,502,646 1,324,220 3,310,067 1,523,170 5,397,837 1,902,617

3,159 237 2,034 122 1,336 804 1,036 614 172 1,346 453 1,329 919 1,082 665 2,271 2,386 1,246 1,780 4,338 1,172

Population Not Served by CWS

Total CWS Total Population Number

Other CWS Total Number Population

Groundwater CWS Total Number Population

Table II. 21 Atrazine/Simazine Major Use States: Numbers of Community Water Systems (CWS), State and CWS Populations


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Table III. 21 Major Use States PLEX Data for Atrazine January 1993 - December 1995

Totals

Groundwater

Surface Water

Other

Number of Samples

58,177

46,187

9,688

2,302

Number of Detections Percent of Detections

5,423 9

1,359 3

3,660 38

404 18

CWS Number of CWS with Data Percent CWS with Data

14,440 42

12,170 43

1,973 41

297 23

Number of CWS with No Detections Number of CWS with Detections

13,169 1,271

11,823 347

1,116 857

230 67

91 9

97 3

57 43

77 23

Major Use State Population Population on CWS Population Served by CWS with Data Percent Major Use State Population Assessed Percent CWS Population Assessed

174,630,000 161,471,531 113,285,471 65 70

70,270,501 44,128,148 25 63

78,027,643 60,482,352 35 78

13,173,: 8,674,9 5 66

Population with No Detections Population with Detections

88,951,223 24,334,248

42,305,650 1,822,498

40,903,324 19,579,028

5,742,2 2,932,7

79 21

96 4

68 32

Data

Percent of CWS with No Detections Percent of CWS with Detections

1

Populations

1

Percent of population with No Detections Percent of population with Detections

' Percent CWS and populations with or without detects are based on the number of assessed CWS and populations respectively.


66 34

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Table IV. 21 Major Use States P L E X Data for Simazine January 1993 - December 1995


Surface Totals

Groundwater

Water

Other

53,791

43,785

7,949

2,057

730 1

101 0.23

595 7

34 2

13,853

11,903

1,641

309

40

42

34

24

13,589 264

11,835 68

1,458 183

296 13

98 2

99 1

89 11

96 4

Data Number of Samples Number of Detections Percent of Detections CWS Number of CWS with Data Percent CWS with Data Number of CWS with No Detections Number of CWS with Detections Percent of CWS with No Detections' Percent of CWS with Detections Populations Population on CWS

174,630,000 161,471,531

70,270,501

78,027,643 13,173,387

Population Served by CWS with Data

110,815,240

44,011,929

57,732,186

Percent State Population Assessed

63

25

33

5

Percent CWS Population Assessed

69

63

74

69

101,578,523

43,529,287

49,965,500

8,083,736

9,236,717

482,642

7,766,686

987,389

92 8

99 1

87 13

89 11

Major Use State Population

Population with No Detections Population with Detections 1

Percent of population with No Detections Percent of population with Detections

'Percent CWS and populations with or without detects are based on the number of assessed CWS and populations respectively.


9,071,125


259 The majority (82%) of the CWS in the 21 states use groundwater as the raw water source (Table II). Thus, the two herbicides' databases contain more groundwater (4-5 times) than surface water samples (Tables III, IV). The databases for both herbicides were also dominated by samples with analytical results reported as nondetections. The limit of detection (LOD) required for the analysis of atrazine and simazine samples varied among the 21 major use states. Sixteen states used an LOD of 4.0 ppb Surface Water 4.0 ppb Groundwater 4.0 ppb Other (Blends) 4.0 ppb Total

Exposure to the Herbicides Atrazine and Simazine ... - ACS Publications

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