Pesticides and Wildlife - ACS Publications - American Chemical Society

Chapter 17

History and Risk Assessment of Triazine Herbicides in the Lower Mississippi River 1

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W. R. Hartley , L. E. White , J. E . Bollinger , A . Thiyagarajah , J. M . Mendler , and W. J. George Downloaded by STANFORD UNIV GREEN LIBR on September 17, 2012 | http://pubs.acs.org Publication Date: November 1, 2000 | doi: 10.1021/bk-2001-0771.ch017

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School of Public Health and Tropical Medicine, Environmental Diseases Prevention Research Center and Division of Toxicology/Pharmacology Department, Tulane University, 1430 Tulane Avenue, New Orleans, LA 70112 2

All available historical water quality data for triazine herbicides in the Mississippi River south of Memphis, TN were characterized for temporal trends and ecological and human health risks. The most abundant of the triazine compounds detected was atrazine, which also represented the largest contribution to the dataset. Temporal analysis of the data indicated no distinct increase in median atrazine concentrations from 1975 to 1997; the median atrazine concentration was 0.47 ug/L (ppb) in the river water. In the 19901994 LA Department of Environmental Quality (LADEQ) survey of Mississippi River fish, atrazine was detected in 1.3% of fish examined, with a maximum concentration of 0.058 mg atrazine/kg fillet (ppm). Based on the safe lifetime dose for atrazine, protection for equivocal evidence of carcinogenicity, the Maximum Contaminant Level (MCL), and ecological criteria, there were no significant health risks due to atrazine from use of the river water as a drinking water source, nor were there significant risks to aquatic organisms.

INTRODUCTION The purpose of this paper is to characterize the water quality data on triazine herbicides in the lower Mississippi River south of Memphis, TN, and conduct health and environmental risk assessment based on temporal trends in the data. We focused on potential health and ecological risks associated with atrazine, cyanazine, and simazine based upon occurrence in the study area and known usage patterns in the © 2001 American Chemical Society In Pesticides and Wildlife; Johnston, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.

225

226 Mississippi River Basin. The triazines are a group of chemically similar herbicides including simazine, propazine, prometryn, prometon, cyanazine, ametryn and atrazine. The USEPA (i) in a 1988 evaluation of the STORET database found atrazine in 4,123 of 10,942 surface water samples analyzed, representing 1,659 surface water locations in 31 states. The 85 percentile value of all non-zero samples was 2.3 ppb. Cyanazine was found in 1,708 of 5,297 surface water samples analyzed, representing 392 surface water locations in seven states. The 85 percentile value for all non-zero samples was 4.11 ppb. Atrazine is one of the most broadly used pesticides in the U.S. based upon pounds of active ingredient applied per year. Primary concerns over the use of triazines are surface and groundwater contamination and subsequent human and ecological health issues. Atrazine is primarily used for general weed control on industrial and other non-agricultural land and selective weed control in crops including corn, sorghum, sugar cane, pineapple, wheat, macadamia nuts, and Christmas trees. Atrazine is also used on turf and lawns and in conifer restoration (2,5). With regard to regulatory status, atrazine is classified as a Restricted Use Pesticide (RUP) due to potential for groundwater contamination. RUPs may only be purchased and used by trained and certified pesticide applicators. In November 1994, the USEPA initiated a Special Review of atrazine including use and health effects aspects (4). In June 1996, the USEPA published a proposed rule prohibiting use of three triazines (atrazine, simazine, and cyanazine) unless USEPA approved State and Tribal management plans were developed. In 1994, 21-34 million pounds of cyanazine were applied to control weeds on cornfields. The use of cyanazine is being gradually phased out and will not be used after December 2002. Five to seven million pounds of simazine and 200,000 to 400,000 pounds of propazine (under emergency exemptions) per year are used (5). th

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Triazine herbicides have been found in Mississippi River water reflecting usage during the past 30 years. DeLeon et al. (5) reported atrazine levels of ND (source), 0.640 ppb (Cario, DL), 1.10 ppb (Memphis, TN), and 0.410 ppb (New Orleans). Larson et al. (6) studied atrazine flux in the Mississippi River from 5/1/91 to 3/1/92 and reported concentrations were highest during May and June, immediately following pesticide application and spring rains and dropped below detection limits in late summer. The authors reported maximum concentrations of 3.6 ppb atrazine in June, 1991, in the Mississippi River near Baton Rouge, LA. During an intense rainstorm event (May 15-17,1990) in Iowa, Illinois, Indiana, and Ohio, the peak concentrations of triazine herbicides in the tributaries of the Upper Mississippi River reached 36 ppb and resulted in an upriver gradient of 0.2 ppb per 100 km (7). During the 1993 flood, Goolsby et al. (8) reported that median (range) atrazine and cyanazine concentrations at six stations on the Mississippi River including Baton Rouge, L A were 2.2 ppb (1.27-3.31) and 1.18 ppb (0.45-1.91) respectively. Pereira and Hostettler (9) evaluated primary sources of atrazine in the Mississippi River. They concluded that inputs of atrazine, cyanazine, and simazine to the Mississippi River (study periods: July-August 1991, October-November 1991, and April-May 1992) are mainly from the Minnesota, Des Moines, Missouri, and Ohio

In Pesticides and Wildlife; Johnston, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.


227 rivers. Their study suggested that during base-flow conditions, there is significant groundwater and surface water interactions in the Mississippi River. Conservative estimates of annual mass transport of atrazine and cyanazine to the Gulf of Mexico were 160 tons and 71 tons respectively. Individual rivers such as the Minnesota River which drains the agricultural region of southern Minnesota annually contributes up to 1-2 tons of atrazine to the Mississippi River (10). In a study by the USGS of contaminants in the Mississippi River from 1987-1992 (11), levels of atrazine were unexpectedly elevated with the highest concentrations near St. Louis, MO, because of inputs from the Missouri and Illinois rivers, associated with drainage from corn fields. However, maximum concentrations of atrazine only exceeded the drinking water Maximum Contaminant Level (MCL) of 3.0 ppb under extreme localized conditions. Concentrations of atrazine dropped rapidly with distance upriver of the Gulf of Mexico. Transport of atrazine in to the Gulf of Mexico was further documented by McMillin and Means (12) in which atrazine was ubiquitous over the entire northwestern Gulf of Mexico coastal shelf area in the spring, summer, and fall.

MATERIALS AND METHODS Water Quality As a central aspect of the Tulane University Mississippi River Database Project, Tulane researchers have developed a database for use as a repository for results from the analyses of water samples collected from the Lower Mississippi River, from just south of Memphis to the receiving waters of the Gulf of Mexico. To date, roughly three million records of over 800 water-quality parameters have been accumulated. These data, collected from analysis conducted by academia, government, industry and municipal water works, were integrated into a.relational information system and GIS, representing the most comprehensive source of water-quality information available on the lower Mississippi River as a single database (13). Triazine herbicide data presented in this report were generated by the Louisiana Department of Environmental Quality (LADEQ) and the US Geological Survey (USGS) through the US Environmental Protection Agencies' Storage and Retrieval System (STORET), as well as through reports in the literature (14,15,16). Additional data were obtained directly from municipal water works (Jefferson Water Works (JWW) and Orleans Water Works (OWW)). Atrazine data were also obtained from the surface water monitoring program conducted by Novartis (formerly Ciba-Geigy Corporation) (17) and other published results from academic sources (5). All data were subjected to a validation process, which removed duplicate records and replaced non-detects with the reported detection limit value for each analytical method used. Visual inspection of the triazine data indicated no apparent outlying points. Variations in triazine concentrations due to sampling location were minimal throughout the study area. This is attributed to the fact that the Lower Mississippi



228 River receives very little discharge south of the Arkansas River confluence (18, 19, 20, 21). The relative abundance of atrazine data allowed for statistical comparisons between source agencies and between filtered and unfiltered water fractions. However, a lack of sufficient overlap between data sets precluded similar comparisons for the other triazine compounds studied. Visual inspection of the various agencies' data with respect to these other triazine compounds revealed no obvious differences in their reported results, with the exception of higher concentrations in the unfiltered samples of simazine and cyanazine. Therefore, where statistical comparisons of data sets were not possible, data from different agencies were assumed comparable and were grouped for ease of display. Filtered and unfiltered fractions for these sets were indicated separately on summary plots. Risk assessment was conducted using the unfiltered samples for simazine and cyanazine as a worst case scenario. Nonparametric statistical comparisons were conducted on weekly means of atrazine data, grouped by source agency or water fraction, to determine whether these data could be integrated into a single large set. Paired sets of data from coinciding weeks were analyzed using the Kruskel-Wallis test (using analysis of variance on rank-transformed data), with a p= 0.05 level of significance (22). Using these statistical methods, data from JWW prior to 1990 were found to be inconsistent with other records available from the same period. These data were therefore not included in continuing analyses. Because no other significant differences were found with respect to source of data (where temporal overlap existed) or between filtered and unfiltered data, the remaining atrazine data were combined for the purposes of temporal characterization and risk analysis.

Health and Ecological Assessment Health and ecological assessment included determination of the potential impact of triazine herbicides on use of the Lower Mississippi River as a drinking water source and on the consumption of fish. The impact of the triazine herbicides in the Lower Mississippi River on aquatic organisms was also considered. With regard to drinking water, two health assessment methods were utilized (1). In the first approach, Margins of Exposure (MOEs) were calculated based upon some of the exposure assumptions of the Safe Drinking Water Act (SDWA) in which the reference dose (RFD) is used as the safe lifetime daily dose and the exposure assumptions are 2 L/day water consumption, 70 kg body weight person and 100% gastrointestinal absorption. The MOE does not, in this case, consider other potential sources of the contaminant. In the second approach, the ratio of the median herbicide concentration to the Maximum Contaminant Level (MCL) is used. The MCL.value is a legal standard and considers both risk assessment and risk management including a relative source contribution of 20% from drinking water, potential carcinogenicity, technical feasibility and economics. Fish consumption (23) exposure assumptions included one fish meal per week (30g fish/person/day), 70kg body weight person, 100% gastrointestinal absorption, and RFD as the safe lifetime daily dose. Cooking method was not assumed


229 to result in any significant contaminant removal. Canadian Government aquatic-life guidelines were used to assess aquatic toxicity. There are currently no US Government guidelines for aquatic toxicity of triazine herbicides.


RESULTS AND DISCUSSION There were approximately 5,368 records located on triazine herbicides compiled from six existing databases (Figure 1). Most of the records came from JWW, Novartis, and LADEQ. The number of available records available by year was skewed. Prior to 1990, only two hundred (200) or fewer records were available per year whereas from 1991-1997 more than 500 records per year available (Figure 2). Atrazine, cyanazine, and simazine were found in measurable concentrations while, when detected, propazine, prometryn, prometon, and ametryn occurred at trace concentrations (Figure 3). Based on previously cited application patterns, it is expected that atrazine, cyanazine, and simazine would be found in ranges to allow characterization whereas propazine, prometryn and prometon were not. Based on these results atrazine, cyanazine and simazine were further characterized in water quality and health and environmental risk assessments. From 1975-93, the atrazine records are primarily from filtered water samples and from 1994- 1998 are primarily from unfiltered water samples (Figure 4). Based on the distribution of the atrazine data on unfiltered and filtered water, this represents primarily a shift in analytical methods. Also considering the solubility of atrazine, the atrazine measured in whole and filtered water are not statistically significantly different to warrant separate analyses of the data sets. The annual median atrazine levels range from 0.2 to 0.7 ppb from 1975-1997. In 1990 and 1993 the annual median concentrations rise to l.Oppb. In both of these years, peak rainfall and/or flood events occurred in the upper Mississippi River (Figure 5). This observation correlates well with previous observations associating usage patterns and rainfall events. A seasonal analysis of the atrazine levels by month (Figure 6) shows expected higher atrazine concentrations in June, July and August which is associated with peak triazine pesticide usage on crops, particularly in the upper Mississippi River. The lower Mississippi River is confined by levees and it is unlikely that substantial loads of atrazine would enter from local agriculture sources except in the event of extreme flooding that has not occurred. Cyanazine in filtered and unfiltered water samples from the Mississippi River (Figure 7) has remained relatively stable based on annual averages throughout the study period with the exception of 1993 for which there was a notable increase, probably due to flooding of the upper Mississippi River.


230


3000

Acad.

OWW

USGS

LADEQ Novartis

JWW

Source Figure 1. Total number of triazine records from 1975-1997 by source agency, including all JWW records.

1975

1980

1985

1990

1995

Year Figure 2. Total number of triazine records available by year including all JWW records.



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Tot. Simazine Diss. Simazine 1Diss. Propazine Diss. Prometryn Diss. Prometon Tot. Cyanazine -| Diss. Cyanazine Tot. Atrazine -| Diss. Atrazine Diss. Ametryn

25%.

50% Z5%

N= 503

90%

10%

Λ/=241 N= 171 N= 190 N= 201

A/=219 A/= 1656 A/= 1411 ΛΝ190

4

5

6

7

8

9

10

11 12

Concentration, ug/L

Figure 3. Concentration and distribution of triazine herbicides from 1975 - 7997.


232

10 Ο)

3


C Ο

Έ ω

1

ο c ο

Ο ω

I

0.1

0.01 1975

1980

1985

1995

1990

2000

Year

Figure 5. Annual atrazine concentrations from 1975-1997 8 ο

7

Atrazine Data LOWESS (É=0.06)

6 o) 5

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Month/ Day of Year

Figure 6. Seasonal distribution of atrazine from combined data (filtered and unfiltered) from 1975-1997



233

Figure 7. Weekly mean concentrations of filtered and unfiltered cyanazine from 1989 -1997


234 Seasonal concentrations of cyanazine were similar to atrazine with increases during the June to August period and relatively trace levels during the remainder of the year (Figure 8). Although plotted together, comparability of filtered and unfiltered fractions was not established.


Simazine (Figure 9) from 1987-1998 show a pattern of increasing concentration beginning in 1992 with the most striking increases beginning in 1996. The causes for this increase in simazine are unknown since there are no unusual rainfall events or flooding in the upper Mississippi River after 1993. A summary of five year intervals showing atrazine median concentrations along with the 75 percentile, 95 percentile, and maximum concentration are provided in Table 1. For atrazine, median values, 75 percentile values and 95 percentile values are similar with the exception of 95 percentile for atrazine for 1980-84 and 1990-94 periods. th

th

th

th

th

Maximum concentrations of atrazine have been declining particularly since 1985. A summary of three-year interval cyanazine and simazine concentrations is also shown in Table 1. For cyanazine the 75 , 95 , and maximum concentration values decreased during the 1995 1997 interval. For simazine, the 95 percentile and maximum concentration value increased from 1995 - 1997. th

th

th

The reference doses for atrazine, cyanazine, and simazine are 0.035, 0.002, and 0.005 mg/kg-bw/day respectively. The MCLs for atrazine and simazine are 3 ppb and 4 ppb respectively. Although the is no MCL for cyanizine, a lifetime health advisory could be calculated using the provisions of the SDWA and would result in an allowable level of 5 ppb to 1 ppb depending on the selection of an additional uncertainty factor for equivocal evidence of carcinogenicity (USEPA, Group C classification). The MOE values in Table 2 indicate that for atrazine, cyanazine, and simazine, the values fall well below MOE 1.0. This indicates that none of the chemicals exceed the safe lifetime exposure dose (RFD). Even if the maximum values detected were encountered for a lifetime in drinking water, they would not exceed the safe dose. Using a worst case additive toxicity model for all three chemicals under the assumption of similar modes of toxicity, the cumulative MOE or Hazard Index (HI) would not exceed 1.0 and thus be considered safe. With regard to the ratio of the median concentration to the MCL, the regulatory standard is not exceeded for atrazine and cyanazine. However, some 95 percentile concentrations and maximum concentrations do exceed the MCL. This poses a legal and regulatory issue that may result in an array of remedies under the SDWA. th

The risks from consumption of triazine herbicides in the lower Mississippi River were determined. The Louisiana Department of Environmental Quality (24), reported that from 1990 - 1994 atrazine was detected in the fillets of fish 1.3% of the time (2 detections) with a maximum concentration of 0.058 mg atrazine/kg fillet. Using this worst case situation, the RFD for atrazine would not be exceeded. Considering the low



235

12

10

d

ο

Unfiltered

Ο

Filtered

8 H •

•2

6

da

ι

Jan

Feb

Mar

Apr

1

1

May

Jun

1-

Jul

~i

Aug

Sep

Oct

1

-

Nov

Dec

Jan

Month/ Day of Year

Figure 8. Seasonal distribution of cyanazine concentrations combined 1989 -1997



236

Figure 9. Weekly mean concentrations offilteredand unfiltered concentrations of simazine from 1988 -1997


237 Table 1. Summary Data on Selected Triazine Herbicides Concentration (ug/L) Median 75% 95%


Date Range

Atrazine, Unfiltered and Filtered 75-79 0.565 1.08 80-84 0.44 1.1 85-89 0.46 0.8 90-94 0.46 1.21 95-97 0.31 1.1 Overall 1.1 0.47

Max

2.47 3.5 2.4 3.33 2.66 2.92

17.8 16 6.2 5.6 4.9 17.8

0.69 0.3

5.97 0.86

10.2 1.44

0.2 0.27

0.43 1.48

1.39 3.79

Cyanazine, Unfiltered: 92-94 95-97

0.151 0.124

Simazine, Unfiltered 92-94 95-97

0.12 0.12

frequency of detection, the chance exposure to significant levels of atrazine through fish consumption is remote. Similar data on fish tissue levels for cyanazine and simazine were not available. To determine risks to aquatic life in the lower Mississippi River, study results were compared to Canadian Government guidelines for atrazine (2 ppb), cyanazine (2 ppb), and simazine (10 ppb). All (Table 1) atrazine, cyanazine, and simazine median concentrations were below the Canadian guidelines. Some 95 percentile and maximum concentrations of atrazine and cyanazine exceeded the Canadian guidelines. We have characterized available historical water quality data from 1975 - 1997 for triazine herbicides in the lower Mississippi River south of Memphis, T N . The most abundant of the triazine compounds was atrazine followed by cyanazine and simazine. The levels of atrazine and cyanazine followed seasonal patterns associated usage of these herbicides in the upper Mississippi River Basin. The use of these two herbicides in crops in the lower Mississippi River has little influence on atrazine and cyanazine levels due to the confinement of the lower Mississippi River by the levee system and the lack of flooding events which would breach the levee system. Upper Mississippi River Basin rain and/or flooding events in 1990 and 1993 resulted in minor increases in atrazine and cyanazine concentrations in the lower Mississippi th


238 Table 2. Systemic Toxicity of Drinking Water Contaminated with Atrazine, Cyanazine, and Simazine.


Date

MOE MOE75th MOE 9?" MOE Max Median/ MCL Median percentile percentile Atrazine ( Unfiltered and Filtered)

75-79

5 χ ΙΟ

80-84

-4

4 x ΙΟ

-4

4

9 χ 10"

-4

9 χ 10

85-89

4

4 x 10"

7 χ 10"

90-94

4

4x 10"

3

95-97

4

3x ny

4

1 χ 10

4

9 χ 10-

Overall

4 x 10"

92-94

2 χ 10"

4

3

3

95-97

2 χ 10

92-94

7x HT

95-97

9 χ HT*

4

4

7x 10"

2 χ 10

3

2 χ 10"

3

3 χ 10" 2 χ 10

3

3 χ 10 2 χ 10

3

0.19

2

2

1 χ 10" 5 χ 10

3

5 χ 10

3

0.15 0.15

3

4 χ 10"

0.10

3

2

0.17

3

2 χ 10

2 χ 10"

Cyanazine (Unfiltered) 2 χ 10·' 1 χ 10 8 χ 10 2

2

3

2

4 χ 10"

1 χ 10

2

2 χ 10'

Simazine (Unfiltered) 8 χ 10 1 χ 10 3 χ 10 3

2 χ 10

3

0.15

3

3

9 χ 10"

2 χ 10

NA NA

3

0.03

2

0.03

River. Although simazine concentrations in the river were low, we are unable to explain increases in the 1996 - 1997 period. We found no indication of increased usage of simazine during the 1996 - 1997 period. Periodic analysis of pollutants such as triazines herbicide data from large databases such as Tulane University River Database Project may provide information to make water quality management and herbicide usage decisions to minimize environmental impacts on the lower Mississippi River. REFERENCES 1. USEPA. Drinking Water Health Advisory: Pesticides - Atrazine; Lewis Publishers Inc., Chelsea, Michigan, 1989, ρ 819. 2. Farm Chemicals Handbook, Meister, T.T Ed.; Meister Publishing Company, Willoughby,OH,1987. 3. USEPA. The Triazine Pesticides, Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, D.C. 1997, p3. 4. EXTOXNET. Extension Toxicology Network, Pesticide Information Profiles -Atrazine; Oregon State University, 1999, p7. 5. DeLeon, I.R.; Christian, J.B.; Peuler, E.A.; Antoine, S.R.; Schaeffer, J.; Murphy, R.C. Chemosphere 1986, 15, 795-805. 6. Larson, S.J.; Capel, P.D.; Goolsby; D.A.; Zaugg; S.D.; Sandstrom, M.W. Chemosphere 1995, 31, 3305-3321. 7. Moody, J.A. and Goolsby, D.A. Environ. Sci. Tech. 1993, 27, 2120-2126.


239 8. 9. 10.


11. 12. 13.

14. 15. 16. 17. 18. 19. 20. 21.

22. 23. 24.

Goolsby, D.A.; Battaglin, W.A.; Thurman, M.E. River. U.S. Geological Survey Circular 1993, 1120-C, ρ19. Pereira, W.E. and Hostettler, F.D. Environ. Sci. Tech. 1993, 27, 1542-1552. Schottler, S.P.; Eisenreich, S.J.; Capel, P.D. Environ. Sci. Tech. 1994, 28, 10791089. Renner, R. Environ. Sci. Tech. 1996, 30, 241. McMillin, D.J. and Means, J.C. J. Chromatography. 1996, 754, 169-185. Preslan, J. E.; Belhouche, B.; Swalm, C. M . ; Hughes, J. M . ; Chen, H-L.; Henry, M . ; Lin, D.; Bakeer, R.M.; Demtchouk, I.; Anderson, M . B.; Regens, J. L.; Means, J. C.; Bollinger, J. E.; Steinberg, L. J.; Luna, R.; Hernandez, R.; Hartley, W. R.; and George, W. J. Environ. Prog. 1997, 16,145-163. Moody, J. Α.; Ed. US Geological Survey Open File Report 94-523, 1995. Pereira, W.E.; Moody, J.J. Hostettler, F.D.; Rostad, C.E.; Leiker, T.J. US Geological Survey Open File Report 94-376, 1995. Coupe, R. H.; Goolsby, D. Α.; Iverson, J. L.; Markovchick, D. J. and Zaugg, S. D. US Geological Survey Open File Report 93-657, 1995. Tierney, D. Ciba-Geigy Corporation Agricultural Group, Technical Report No. 6-92, Greensboro, North Carolina, 1992. Sabins, D. S. Clean Enough? A conference on Mississippi River water quality (Proceedings), Lake Pontchartrain Basin Foundation, Metairie, 1997, p32. Wells, F. C. US Department of the Interior, Water Resources Technical Report No. 21, Baton Rouge, Louisiana, 1980. USACOE. US Army Corps of Engineers report, Vicksburg, Mississippi, 1976, p3. Everett, D.E. Hydrologic and quality characteristics of the lower Mississippi River, Louisiana Department of Public Works, Technical Report No. 5, Baton Rouge, Louisiana. 1971, ρ 48. Helsel, D. R. and Hirsch, R. M. Statistical Methods in Water Resources. Studies in Environmental Science 49 Elsevier, New York, 1993, p529. USEPA. Guidance for Assessing Chemical Contamination Data for Use in Fish Advisories, Vol. II, EPA 823-B-94-004, Washington D.C. 1994. LADEQ. Mississippi River Toxics Inventory Project, Louisiana Department of Environmental Quality, Baton Rouge, Louisiana, 1995, p29.


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