Applications of the California Pesticide Use Reporting Database in

(PUR) database of the California Department of Pesticide. Regulation. Actual locations and dates of applications of active ingredient allow for effect...
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Chapter 15

Applications of the California Pesticide Use Reporting Database in More than 25 Years of U.S. Geological Survey Hydrological Studies Joseph Domagalski* and James Orlando U.S. Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento, California 95819, United States *E-mail: [email protected]

The U.S. Geological Survey (USGS) has been collecting data on the occurrence of pesticides in California surface and ground water since the 1970’s. The design of these studies benefited from the availability of the Pesticide Use Reporting (PUR) database of the California Department of Pesticide Regulation. Actual locations and dates of applications of active ingredient allow for effective design of studies that seek to understand which compounds can be mobilized from the point of application as well as the hydrological or climate-related factors that enhance the off-site transport. Key studies from the 1970’s to the present are discussed here and demonstrate how the USGS both designed studies and improved their analytical methodology to keep up with changes in how pesticides are used in California.

Introduction The U.S. Geological Survey (USGS) has been collecting and analyzing data on the occurrence of pesticides in surface and ground water in California and other states since the 1970’s. Representative publications include (1–15). Water and sediment pesticide concentration data collected from 1990 to 2010 were compiled by Orlando (16). These studies typically had a regional focus such as the occurrence of pesticides in a large aquifer system or systems, or status and trends of pesticides in rivers and their linkage to aquatic toxicity. More specific studies included targeting high discharge events after storms and concentrations Not subject to U.S. Copyright. Published 2018 by American Chemical Society

of pesticides at various portions of storm hydrographs. The design of these studies is often dependent on the knowledge of which pesticides are used on specific crops, the exact location of application, and the timing of application. For example, knowledge of specific pesticide applications, as well as the location and the timing of the applications relative to storm events, aid understanding the causes of observed toxicity to various organisms in river water samples. This allows for an understanding of how, when, and where pesticide mobilization may occur. Knowledge of the total amount of pesticides applied and sufficient sampling of river water at a stream gauging station may allow for an estimate of mass load as a percent of use, thereby allowing the ability to calculate how much of the applied pesticides left the application areas. The Clean Water Act (https://www.epa.gov/tmdl) requires that management plans, usually a total maximum daily load plan (TMDL), must be put into place if an impairment, such as toxicity due to pesticides, has been identified. The USGS has consistently utilized the pesticide use reporting (PUR) database maintained by the California Department of Pesticide Regulation (CDPR) for the design and interpretation of water quality studies (http://www.cdpr.ca.gov/docs/pur/purmain.htm). These studies were mostly designed to assess transport of pesticides from areas of applications. In some cases, toxicity analyses were also performed. Not all pesticides that are applied in a watershed may be mobilized to a stream, and knowledge of application in vulnerable areas can lead to effective management plans. Pesticide properties such as water solubility and soil water partitioning will have a major effect on subsequent transport or degradation. Pesticides that are detected in groundwater are presumed to be sourced close to the location of the sampling well. An understanding of the geo-hydrologic conditions and agricultural practices that are likely to promote pesticide transport to groundwater can be useful in managing application in similar areas. Although the USGS is not responsible for developing or enforcing TMDLs, water quality studies completed by the USGS aid TMDL development as all USGS data are publicly available and interpretative manuscripts are generally written at the close of a particular study that describe pesticide occurrence in light of hydrological conditions and use. This chapter describes studies conducted since the mid-1970’s that greatly benefited from the PUR database.

Methods, Data Sources, and Study Areas Since 1990, the CDPR has had in place a full use reporting system that requires pesticide applicators to provide detailed information on pesticide use (http://www.cdpr.ca.gov/docs/pressrls/dprguide/chapter9.pdf). Pesticide use data reported by agricultural applicators contain information including the date and time of application, location of application to the section level as referenced by the public land survey system, pesticide product applied and amount, and the crop to which it was applied. The township and range system is described in detail at: (https://nationalmap.gov/small_scale/a_plss.html). There are 36 sections in a township grid, and therefore each section is one square mile (2.59 324

km2). The database reports total amount applied, and total area treated, with location of the application specified to the section level. However, area treated in a particular application is almost always smaller than a section (smaller than 2.59 km2). Pesticides applied by licensed applicators in urban settings (primarily for landscape maintenance and structural pest control) are reported with less detail, giving the product and amount applied but only the month of application and the county in which the pesticide was applied. The CDPR reporting system does not contain information on pesticide applications made by homeowners using products purchased at retail stores. Researchers can process and analyze pesticide use data with a geographic information system (GIS), such as ArcMap. In past studies, river reaches of interest were obtained from various sources and in more recent times, rivers are mapped with the National Hydrography Dataset (NHDPlus) version 2 (http://www.horizon-systems.com/nhdplus/). Use of the NHDPlus system allows for mapping of watersheds of any size, greatly facilitating the design of a hydrologic investigation. Studies discussed in this chapter span both regional groundwater sampling and a variety of river studies. Methods used for the collection, processing, and chemical analysis for pesticides have changed over the years, and specific details are given in the references cited for each study. Most of the study areas mentioned in this chapter are wholly contained in California, although a few studies were completed in a multi-state area or nationally. A map of California with generalized locations of most of the study locations is shown in Figure 1. Many of the studies were conducted in California’s Central Valley, the Sacramento-San Joaquin Delta Region, and San Francisco Bay region because of the high amount of agricultural activities in the watersheds or their ecological significance. Some studies included other regions such as the Salinas River Valley, Central California coast, and the Salton Sea.

Regional Aquifer-System Analysis Study The Regional Aquifer-System Analysis study of the USGS was initiated in 1978 and prompted by the 1977 drought. The study had a national focus and it was funded through the appropriations bill of the 95th U.S. Congress (https://pubs.er.usgs.gov/publication/cir1002). Many of the investigations were completed between 1978 and 1984 and the results of this study for the San Joaquin Valley of California were published in 1991 (3) and 1992 (4). This study area was wholly contained within the San Joaquin Valley of California (Figure 1). As part of this study, the USGS sampled wells throughout the San Joaquin Valley and in addition, data collected by California State agencies, such as the California Department of Health Services, were part of the assessment. At the time of the study, the California Department of Food and Agriculture maintained a well inventory database of well locations and pesticide detections (17). The USGS also collected water samples throughout the valley to supplement the State data and to increase the number of compounds analyzed for the assessment. A number of pesticides that were used at the time in California agriculture were analyzed at detection limits that ranged from 0.01 to 2 micrograms per liter (3). 325

Pesticides detected in that study were mostly herbicides and some soil fumigants. Herbicides included atrazine, bromacil, dicamba, diuron, prometon, prometryn, propazine, and simazine. Soil fumigants included dibromochloropropane and 1,2dibromoethane. Insecticides were generally not detected, with the exception of one or two wells with a detection of the organophosphate insecticide, diazinon, at a detection limit of 0.01 micrograms/L. The regional aquifer system of the San Joaquin Valley includes an unconfined aquifer in the eastern San Joaquin Valley, and both a confined and unconfined system in the western portion of the valley. Wells were selected in both portions of the aquifer. In addition to pesticides, USGS measured tritium in order to discern which portions of the aquifer had relatively modern water.

Figure 1. Map of California showing locations of the Sacramento and San Joaquin Basins, the Central Valley, Sacramento San Joaquin Delta, Salton Sea, and selected rivers. (see color insert)

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Two contrasting herbicides with different amounts of use were diuron and bromacil (Figure 2). Diuron (Figure 2) use was widespread throughout the San Joaquin Valley while that for bromacil (Figure 2) was more localized. In the northern portion of the San Joaquin Valley only two wells had detectable diuron, while diuron was detected more frequently in the southern portion of the Valley, and primarily along the eastern edge of the Valley near the Valley margin (Figure 3). These detections on the eastern portion of the Valley were explained by the high use in this region (Figure 2) with much of the use on orchards, a shallow water table, and coarse-grained soils. Groundwater levels were near to or less than 10 meters below land surface in much of that region resulting in a short travel time from land surface to the water table. The occurrence of tritium in wells with pesticide detections confirmed that recent recharge was affecting the water quality in these shallow wells. In contrast to diuron, bromacil applications in the late 1980’s to early 1990’s were primarily restricted to the eastern edge of the San Joaquin Valley and mainly on orange orchards. Similar to diuron, bromacil has a half-life in soil sufficiently long to be transported to groundwater in these areas of coarse soil and shallow water table (18, 19). Understanding of the relationships between bromacil occurrence, half life, and land use can lead to an effective management strategy.

Figure 2. Use of Diuron and Bromacil in the San Joaquin Valley, 1990 (19). (see color insert)

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Figure 3. Wells sampled for diuron and bromacil in the southern portion of the San Joaquin Valley and land uses (19). (see color insert)

Organophosphate Insecticide Studies Organophosphate insecticides were extensively used in California stone fruit orchards in the 1990’s, and there was considerable interest in monitoring of toxicity attributable to pesticides and other contaminants in water in San Joaquin and Sacramento Valley streams. Water was frequently found to be toxic to the water flea, Ceriodaphnia dubia, with toxicity identification linking this to the organophosphate insecticides diazinon and chlorpyrifos (20, 21). Toxicity was particularly widespread during the winter months as the insecticides were applied to dormant trees in order to control potential insect outbreaks prior to the spring flowering (22–24). From 1991 to 1994, the USGS initiated a sampling program on the lower San Joaquin and Sacramento Rivers with water samples collected 2 to 3 times a week. This sampling program documented the high detection frequency of organophosphate insecticides and some herbicides. Toxicity testing of water from the same locations prompted the California Central Valley Water Quality Control Board to initiate a total maximum daily load (TMDL) program to improve water quality (https://www.waterboards.ca.gov/rwqcb5/water_issues/ tmdl/central_valley_projects/central_valley_pesticides/index.shtml). In order to support the design of the TMDL, the USGS collaborated on a study with the Central Valley Board to document the concentrations and loads of pesticides in rivers following winter storms (6, 7). Diazinon and chlorpyrifos use records, obtained from the California Department of Pesticide Regulation (http://www.cdpr.ca.gov/docs/pur/purmain.htm), were used to locate potential high input tributaries to sample. Pesticide use records indicated that orchards were most likely to be sprayed with dormant spray pesticides such as diazinon during January and February (Figure 4). 328

Figure 4. Use of diazinon on all crops in the Sacramento Valley from 1995 to 2000, color coded by month during the dormant tree period. (see color insert)

Pesticide use records indicated that diazinon use in the Sacramento Valley was heaviest upstream of Sacramento in the lower Feather and Yuba River basins (Figure 5). A detailed investigation of 17 sites (Figure 6) provided necessary information to help inform how concentrations vary during a storm and what the associated loads are relative to use. It was expected that concentrations would be highest nearest to application locations and lowest near the mouth of the river basins. This was born out as demonstrated in Figures 7 and 8. Concentrations at Wadsworth Canal (Figure 7) were highest during the first storm, which occurred near the beginning of February. River discharge, as indicated by river stage, did not rise as much during this storm as it did in the subsequent storm in mid-February. River stage is defined as the level of the river relative to a defined reference altitude. River stage rises during a rainfall runoff event. This is typical as soil profiles need to be close to saturation in order to generate runoff. During the mid-February storm, concentrations were elevated in the rising portion of the hydrograph, and then dropped off as more water in the stream diluted the diazinon concentration. A similar pattern was observed downstream at the Feather River at Nicolaus located just above the confluence of that river with the Sacramento River (Figure 8). Similar to the pattern observed at the Wadsworth Canal, concentrations were higher during the earlier storm at the beginning of February, relative to the mid-February storm, typical of a “first flush” event. Although measurable concentrations occurred in the rising portion of the hydrograph of the mid-February storm, concentrations rapidly dropped because of the much higher discharge. 329

Figure 5. Diazinon use on all crops within the Sacramento Valley, between December 1999 and March 2000 (6). (see color insert)

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Figure 6. Sampling sites in the Sacramento Valley, storm water runoff study (6).

Mass loads of pesticides were calculated using the discharges of both the Feather River near Nicolaus and the Sacramento River in Sacramento. Having the application rates of diazinon from the California Department of Pesticide Regulation allowed for a calculation of load as a percentage of use. Those calculations for these storm events are shown in Table 1. Both the Feather River and Sacramento River are large rivers, and collectively transported about 0.44% of the total amount of pesticides applied in the upstream orchards or fields. The percentages reported in California are similar to those found in other watersheds of the United States (25), calculated using county-level sales reported by (26). The advantage of using the CDPR PUR database is that “hot spots” of applications can be traced and potential best management practices implemented.

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Figure 7. Diazinon concentrations at the Wadsworth Canal sampling location by gas chromatography/electron capture detector or thermionic specific detector or enzyme-linked immunoassay (6).

In a follow-up study (8), trends in pesticide concentrations from several locations in the western United States were studied. By the time of that study, concentrations of diazinon in California streams were decreasing (Figure 9), and mostly meeting the requirements of the TMDL by the year 2004. This can be attributed to the drop in use of diazinon over a 14-year period (Figure 10). Chlorpyrifos is also shown on Figure 10, as it is another organophosphate insecticide targeted for load reduction by the California Central Valley Water Quality Control Board.

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Figure 8. Diazinon concentrations at the Feather River near Nicolaus sampling location by gas chromatography/mass spectrometry or enzyme-linked immunoassay (6).

Table 1. Diazinon load as a percentage of use in respective watersheds, Feather River pesticide study (6, 7). River Site

Diazinon use in kilograms of active ingredient

Diazinon load at river location

Diazinon load as a percentage of use

Feather River Near Nicolaus

1,982

5

0.25

Sacramento River in Sacramento

9,117

17.7

0.19

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Figure 9. Time series of diazinon concentration percentiles at two locations: Orestimba Creek (agricultural stream) and the San Joaquin River at Vernalis (large river) (8). (see color insert)

Figure 10. Use of chlorpyrifos and diazinon in the San Joaquin Valley during the dormant tree period (December to March) on all crops, 1991 to 2005. (see color insert)

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Irrigation Season Study Domagalski and Munday (9) made extensive use of the pesticide-reporting database in a study of the detection frequency of pesticides in the San Joaquin Valley during the irrigation season (March through October). One example from that study is shown in Figure 11, where detections of the herbicide trifluralin in the San Joaquin River could be attributed to hot spots of trifluralin use upstream. Relatively high use in the regions west of the San Joaquin River, in areas of clay soils and extensive irrigation season runoff, result in downstream transport. In contrast, although trifluralin was used in the eastern portion of the valley, detection frequencies there were much lower and this was attributable to lower amounts of irrigation runoff due to coarse-grained soils.

Figure 11. Use of trifluralin in the lower San Joaquin River Basin, and detection frequency at sampling locations (9). (see color insert)

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Expansion of USGS Laboratory Capabilities and Subsequent Studies The USGS operates a number of laboratories with capabilities for the analysis of pesticide residues in water and sediment. The National Water Quality Laboratory in Denver, Colorado (https://nwql.usgs.gov) has the highest throughput of samples. Another laboratory, the Kansas Organic Geochemistry Laboratory (https://ks.water.usgs.gov/research-lab), focuses on nitrogen-containing herbicides, other herbicides including glyphosate and its degradates, antibiotics, and algal toxins (https://ks.water.usgs.gov/current-analytical-methods). Because of the unique nature of California agriculture, relative to other parts of the nation, the USGS Pesticide Fate Research Group (https://ca.water.usgs.gov/ projects/PFRG/) has established analytical methods for a wide suite of current-use pesticides and pesticide degradates, with the goal of understanding the fate of these contaminants in California. Current analytical methods for sediment and water can be found at: https://ca.water.usgs.gov/projects/PFRG/AnalyticalMethods.html. Pesticide use is constantly changing as new pesticide products are brought to market, older pesticides are regulated or phased out of use, and in response to changes in cropping practices. In an effort to keep up with this changing landscape USGS laboratories are constantly developing new analytical methods.

Salton Sea Basin The Imperial Valley/Salton Sea Basin (Figure 1) is one of California’s most productive agricultural areas, the result of a year-round growing season and ample Colorado River water supplied to the region via an extensive irrigation network. A wide variety of crops are grown in the region, which results in high pesticide use and two distinct use periods. As a follow-up to several earlier studies (27–29) and in support of TMDL development by the California State Water Resources Control Board, the USGS Pesticide Fate Research Group (PFRG) conducted a study in 2006-2007 that analyzed water and suspended sediment for 61 and 87 current-use and organochlorine pesticides, respectively (11). In planning for this study PFRG researchers mined the DPR PUR database to determine key periods of pesticide application. Figure 12 shows the two distinct peaks in pesticide application in the basin along with the periods selected for monitoring. Data in the PUR were also used to determine areas of intense pesticide application, which coupled with knowledge of the region’s complex surface and subsurface irrigation and drainage networks allowed for the citing of monitoring locations downstream of critical drainage nodes on the Alamo and New rivers (Figure 13).

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Figure 12. 2006 agricultural pesticide applications (excluding sulfur) in the combined Alamo/New River watershed along with Fall 2006 and Spring 2007 surface-water sampling periods. Applications are expressed as kilograms of active ingredient. (see color insert)

During the study, 25 pesticides were detected in water samples and 34 were detected in suspended sediments. Maximum dissolved concentrations for most pesticides were observed in samples from the Alamo River. A greater number of dissolved pesticides were detected during the Spring than the Fall, and concentrations were more often at their maxima during Spring. The highest measured concentration was 8,940 ng/L for EPTC at the Alamo River Niland location. Four current-use pesticides (carbofuran, chlorpyrifos, diazinon, and malathion) were detected in water samples at concentrations above established U.S. EPA aquatic life benchmarks. Twenty current-use pesticides were detected in suspended sediments including pyrethroid insecticides and fungicides. Fourteen legacy organochlorine pesticides were also detected in these samples, however only p,p′-DDE concentrations were consistently above the method detection limits. All detection limits are given in the published reference (11). Greater numbers of current-use and organochlorine pesticides were detected in Alamo River suspended sediments than in the New River sediments. Of the 22 pesticides detected in suspended sediments in both rivers, 16 had their maximum concentrations in Alamo River samples. In general no seasonal differences were observed for pesticides detected in suspended sediments.

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Figure 13. Map of sampling sites and major agricultural drains on the Alamo and New Rivers. (see color insert)

Currently, the Salton Sea and nearby areas in the basin are under intense ecological stress due to a decline in the level of the Salton Sea resulting from water transfers from agriculture in the basin to urban areas in Southern California. Projects are currently under way or in development which would create over 12,000 ha of restored saline and fresh water habitat (30). One complicating factor in this process is that the major source of water for these projects is agricultural return water and the quality of this water continues to be impacted by contaminants including current-use pesticides.

California Central Coast Agricultural regions along California’s central coast produce much of the nation’s strawberries, lettuce, artichokes, and crucifer crops during a nearly year-round growing season. The region can be divided into three major watersheds, which are drained by the Salinas, Pajaro, and Santa Maria rivers. These rivers each drain into small coastal estuaries, which are some of the most ecologically important and critically threatened habitats in California. The location of the Salinas River is shown in Figure 1. Runoff from irrigated 338

agriculture constitutes a significant portion of flow in these rivers during most of the year. Studies have documented pesticide occurrence and biological effects from pesticides in the rivers and estuaries of the Pajaro (31), Salinas (32), and Santa Maria (33). A study was conducted by the USGS PFRG in 2008-2009 which was designed to provide the California State Water Resources Control Board with data for an initial assessment and characterization of pesticides in these watersheds with a focus on understanding the occurrence of pesticides in the river estuaries (13, 34). The PUR database was employed in several ways during the course of the USGS study. Trends in pesticide use during the early 2000’s showed that two rarely monitored classes of fungicides (azoles and strobilurins) were increasing in use. In response, several of these compounds were added to the PFRG analytical suite. The laboratory also added the carboxamide fungicide, boscalid. The USGS Central Coast project was the first study to document detections of the fungicides azoxystrobin, boscalid, iprodione, and pyraclostrobin in field-collected fish (13). PUR data were also used during this study to compare observed concentrations of boscalid in water samples collected from the Santa Maria estuary to applications of this fungicide in the upstream watershed (Figure 14). During this study 38 different pesticides were detected in water and 22 pesticides were detected in sediments. The types of pesticides detected were similar among estuaries. The fungicide boscalid was the most frequently detected pesticide in all watersheds and was detected at the highest maximum concentration overall (approximately 300 ng/L). The boscalid detection frequency for the Orcutt Creek site was 100%. Detection frequencies for most pesticides were higher in the Santa Maria River estuary watershed than the Pajaro and Salinas River estuary watersheds. A greater number of dissolved pesticides were detected during storm events than during the dry season, and concentrations were often at their maximums during storm events. In estuary bed sediment samples p,pʹ-DDE was detected most frequently. In suspended sediment samples, no compound was detected in more than 50 percent of the samples during the dry season, however eight pesticides were detected in more than 50 percent of the samples during storm events (34). Fish and sand crabs collected near the mouth of the Santa Maria estuary accumulated a number of current-use fungicides, herbicides, and insecticides. The fungicide, pyraclostrobin, was detected in 100% of the fish and sand crabs collected and this is the first study to report its accumulation in tissue. This is also one of the first data sets to report concentrations of a wide variety of current use pesticides in fish and sand crabs (13).

Central Valley and Sacramento/San Joaquin Delta California’s Central Valley (Figure 1) supports a wide variety of agriculture as well as several large urban centers both of which have been well documented as sources of current-use pesticides. Many water bodies within the Central Valley are impacted by current-use pesticides; the California State Water Resources Control Board and U.S. EPA currently list nearly 2,400 km of Central Valley streams 339

as impaired due to pesticides and it is likely that the presence of current-use pesticides and other contaminants play some role in these declines (35). Much of the Central Valley drains into the Sacramento/San Joaquin Delta (Delta), an area of critical habitat for numerous species of concern, including Chinook salmon and the threatened delta smelt. In recent years, multiple pelagic species within the Delta have been in sharp decline (36). The USGS PFRG conducted several studies over the last decade in an effort to better understand the occurrence, transport, and fate of current-use pesticides in the Central Valley and Delta. The PUR database played an important role by providing information on trends in pesticide use (Figure 15), which helped prioritize pesticides to be evaluated during the laboratory’s analytical method development process. The number of pesticides analyzed by the laboratory increased through the addition of a new liquid chromatography tandem mass spectrometry method (37) and through the addition of new pesticides to existing analytical methods (Table 2).

Figure 14. Concentration of the fungicide, boscalid, in water (ng/L) at the upper (•) and lower (○) estuary sites collected between February and October 2008 compared to weekly boscalid use (gray bars) in the Orcutt Creek watershed.

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Figure 15. Example graphic showing trends in pesticide use in the Sacramento/San Joaquin Delta watershed, which was used in prioritization of pesticides for method development. (see color insert)

Table 2. Numbers of pesticide analytes for USGS PFRG studies conducted in the Central Valley and Delta since 2011. Year

Study

Number of Pesticides Analyzed in Water

Number of Pesticides Analyzed in Sediment

Reference

2011-2012

Suisun Bay

99

0

(38)

2012-2013

Delta Inputs

99

0

(39)

2015

Liberty Island

149

124

(40)

In addition to the individual report references listed above, data from these studies is available from the USGS National Water Information System database (https://waterdata.usgs.gov/ca/nwis).

Summary The Pesticide Use Reporting database of the California Department of Pesticide Regulation is a valuable tool for management of agricultural systems and for designing studies related to the safe use of pesticides. Utilizing the information on locations and timing of application significantly helped numerous studies conducted by the U.S. Geological Survey. In addition, the development of new analytical methodology for measuring residues in water and sediment is facilitated by knowing which compounds are being used under changing 341

regulatory requirements or product substitution. This chapter focused on the time frame of the mid-1970’s to the present. The USGS will continue to make use of this database for interpretative studies for the foreseeable future.

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