Soilworks products are the industry’s top standard due to our insistence on creating high performance soil stabilization and dust control products that stand up to rigorous testing – both in the lab and in the field. Our commitment to quality and performance has led to our involvement and testing in hundreds of real-world situations. The following library of reports, presentations, specifications, approvals and other similar documents provide you, our customer, the transparency and dependable assurance that is expected from Soilworks.
Evaluation of dust palliatives used in Alaska highlights Durasoil® and Soiltac® for their effectiveness and environmental compatibility in dust control and soil stabilization. Durasoil, a synthetic organic fluid, provides long-lasting, non-water-dependent suppression of airborne particles, ideal for unpaved roads, work pads, and remote infrastructure projects in extreme climates. Soiltac, a copolymer emulsion, binds and seals soil surfaces, creating a durable crust that resists wind and water erosion, making it well-suited for slope stabilization, access roads, and exposed soil areas. Both products demonstrated low aquatic and terrestrial toxicity, supporting their use in environmentally sensitive and compliance-driven applications. Contact Soilworks for solutions tailored to challenging project environments where operational performance and environmental stewardship are priorities.
EPA/600/R-20/81| March 2020 | www.epa.gov
U.S. EPA Region 10 Air and Radiation Division Tribal Air Program
and
U.S. EPA Office of Research and Development
Center for Environmental Measurement & Modeling
Watershed & Ecosystem Characterization Division Multimedia Methods Branch
EPA Contract: EP-C-17-017
Task Order: 68HERC19F0094
September 3, 2019
Submitted to:
U.S. EPA Region 10 Air and Radiation Division
Tribal Air Program and
U.S. EPA
Office of Research and Development
Center for Environmental Measurement & Modeling
Watershed & Ecosystem Characterization Division
Multimedia Methods Branch
The United States Environmental Protection Agency (U.S. EPA), through its Office of Research and Development (ORD), funded and managed the research described here in under contract EP-C-17-017 to Eastern Research Group. This document has been reviewed by the U.S. EPA, ORD, and approved for publication. Mention of trade names and commercial products does not constitute endorsement or recommendation for use.
Primary Documentation Search………………………………………. 3-6
Palliative Toxicity…………………………………………………………. 3-9
Chemical Make-up of Palliatives………………………………….. 3-11
Frequency of Specific Palliative Use in Alaska……………….. 3-11
Products with the Least Available Toxicity Data…………….. 4-12
Products with the Most Available Toxicity Data……………… 4-12
Frequency of Palliative Use in Alaska……………………………. 4-12
Input from Subject Matter Experts………………………………… 4-13
Step 1: Compare Ecological Toxicity Using Available Data 5-16
Step 3: Extrapolate Ecological Toxicity Data (LC50s) to Mammalian Toxicity (LD50s)……………………………………………….. 5-20
Step 4: Compare Mammalian Toxicity Data (LD50s) to Common Household Products……………………………………………….. 5-24
Step 5: Extrapolate Mammalian Toxicity (LD50s) to HEDs 5-25
Computational Evaluation Conclusions………………………….. 5-26
Figure 5. Regression Based on Data from Hodson (1985)……………………………………………………………………………………………………… 5-23
Table 1. Palliatives Used in Alaska and Included in the 2015 Literature Review: Product Names, Manufacturers, Types, and Chemical Compositions……………………………………………………………………… 3-4
Table 4. Toxicity of Durasoil, EK-35, and EnviroKleen……………………………………………………………………………………………………… 5-17
Table 6. LC50 Rainbow Trout Toxicity of Household Items……………………………………………………………………………………………………… 5-20
Table 7. Regressions for Fish LC50s and Rat LD50s……………………………………………………………………………………………………… 5-21
Table 9. Oral Rat LD50 Toxicity of Household Items……………………………………………………………………………………………………… 5-25
Table 10. Human Equivalent Doses in mg/kg……………………………………………………………………………………………………… 5-25
Eastern Research Groups, Inc. (ERG), a contractor to the U.S. Environmental Protection Agency (EPA), helped EPA evaluate the potential toxicity of dust palliatives used in Alaska. This is a follow-on task to a research effort that ERG assisted the Agency conduct in 2015 (see EPA, 2016 for more information). This current effort in 2019 involved a three-pronged approach, which included (1) performing a targeted literature review to obtain relevant information published since the 2015 literature review effort related to this topic, (2) evaluating literature review findings to identify three palliatives for a computational evaluation, and (3) conducting a computational evaluation to assess the potential toxicity of the three selected palliatives.
This report provides details on activities performed during the targeted literature review, the selection of three palliatives for the toxicity evaluation, and the computational evaluation; summarized findings from each component of the effort; and identified data gaps/research needs. This information is organized into five main sections: “Background,” “Targeted Literature Review,” “Selection of Three Palliatives for the Computational Evaluation of Toxicity,” “Computational Evaluation of Potential Palliative Toxicity,” and “References.”
Unpaved road surfaces are commonplace in Alaska, where more than 50 percent of state-owned roads and the majority of local and private roads are unpaved (UAF/AUTC, 2013). Various sources can cause releases of fugitive dust, such as vehicles (e.g., all-terrain vehicles [ATVs]) traveling on unpaved road surfaces (e.g., dirt roads, gravel roads, unpaved runways), and wind blowing across these surfaces and gravel pits (ADEC and EPA, 2018). Much of the fugitive dust in Alaska comprises particulate matter that is less than 10 microns in size (PM10), which can lead to adverse health effects in some exposed individuals (Withycombe and Dulla, 2006). Fugitive dust has other potential negative impacts, such as impairing driver safety by reducing visibility and requiring costly and frequent road and runway maintenance (UAF/AUTC, 2013).
Dust palliatives are products used worldwide to suppress fugitive dust. For several decades in the state of Alaska, tribal, state, urban, and rural city governments have been applying palliatives to control and suppress dust on unpaved road surfaces. Palliative use dates back to the 1960s with the application of salt-based palliatives, such as calcium chloride and magnesium chloride (Connor, 2015). Due to availability, effectiveness, and cost, common palliatives used in Alaska include water, salt-based palliatives, synthetic fluids, and polymers (Milne, 2015).
EPA (2016) documents all of the different types of palliatives used in Alaska as reported by the State of Alaska Department of Transportation & Public Facilities (Alaska DOT&PF), locations in the state where application is generally known to occur, and typical application methods (see Section 4.1 in EPA, 2016 for more information). In 2015, ERG assisted EPA by performing an extensive literature review to investigate dust palliatives used on road surfaces in the state of Alaska, the fate and transport of these palliatives in the environment, the documented effects to human health and the environment, and the applicable regulations associated with palliative use in Alaska. The findings of that report are documented in EPA, 2016. The purpose of this report is to summarize the follow-on effort performed in 2019.
The use of palliatives in the state of Alaska has raised various concerns, including the potential impacts on traditional subsistence resources, possible effects on the environment, and unknown human health risks from exposure.
Several rural communities have expressed concerns about palliatives through Alaska Department of Environmental Conservation (ADEC) Rural Alaska Road Dust Surveys, which have been conducted periodically since 2007. Using findings from these surveys, ADEC concluded that out of 142 participating communities, 90% reported that dust is a problem in their communities. Approximately one-third (about 47) of the communities surveyed reported at least some use of dust suppressants. In addition, over half of the responding communities (>71) were willing to try chemical-based dust palliatives, but they expressed various concerns such as about their potential toxicity, effects on human health, impacts on the environment, and possible effects on subsistence resources (ADEC and EPA, 2018).
Many data gaps and research needs were acknowledged during the last effort (EPA, 2016), such as no documentation about specific impacts to humans or subsistence foods exposed to palliatives. While this previous research did not locate documented information on possible impacts to subsistence resources, subject matter experts referenced anecdotal information from local residents concerned about salt-based palliative components. For instance, residents were concerned about calcium chloride negatively affecting the taste of subsistence berries and fish (Connor, 2015b) and chloride salts without moisture breaking down into dust, becoming airborne, and then landing on berries and fish left outside to dry (Hickman, 2015a).
Based on data gaps identified during the previous effort, EPA initiated this follow-on task in 2019, seeking to determine the potential toxicity of palliatives commonly used in Alaska, which is of great concern to the Alaska Native population.
This follow-on project, similar to the previous 2015 effort, was created in direct response to questions received from a number of Alaskan tribes and communities about the safety of dust suppressant products. The overarching goal is
to evaluate existing knowledge and data gaps on the potential toxicity of palliatives used in Alaska as they relate to possible exposures among the Alaska Native population. Evidence compiled for this project is intended to assist EPA in communicating the relative toxicity of palliatives used in the state, particularly in the context of impacts on subsistence resources and the potential risk to Alaska Natives. To achieve this overarching project goal, the data compilation process focused on addressing the individual objectives stated in Section 2.3
The defined objectives of this project include the following:
The overarching question EPA sought to answer was: What is the relative toxicity of some of the most commonly used palliatives in Alaska? This project seeks to address the following specific questions:
This section will detail the approach, findings, and data gaps/research needs for the targeted literature review conducted for this project.
The primary purpose of the targeted literature review was to obtain information on the chemical make-up, relevant toxicity values (fish, mammal, plant, invertebrate), and frequency of use for the 17 palliatives identified in the previous project (EPA, 2016) and presented in Table 1. In addition, any documentation was sought related to newer regulations or advisories applicable to palliative use and exposure initiated since the 2015 literature search. This initial toxicity information was used to help inform EPA’s selection of the three palliatives to focus on in the computational evaluation of toxicity (Section 5).
| Product Name | Manufacturer | Type | Chemical Composition / CASRN |
| Alastac | Apun, LLC | Organic nonpetroleum-based
(tall oil) |
• Lignosulfonate (CASRN 8062-15-5) (no percentage provided) |
| AlastaSeal | Apun, LLC | Organic nonpetroleum-based (tall oil) | • Water (34.5-64.5%)
• Proprietary pitch/rosin blend (30-60%, CASRN 8016-81-7) • Additives (5.5%) |
| DirtGlue | GeoCHEM | Polymer | • Water (<52%)
• Aqueous acrylate polymer (>45%, non-hazardous) • Additive (<3%, proprietary) • Aqueous ammonia (<1%) |
| Dowflake | Occidental Chemical Corporation | Salt-based | • Calcium chloride (83-87%, CASRN 10043-52-4)
• Water (8-14%) • Potassium chloride (2-3%, CASRN 7447-40-7) • Sodium chloride (1-2%, CASRN 7647-14-5) |
| Durasoil | Soilworks | Synthetic liquid | • Non-petroleum synthetic alkane fluid
• A complex mixture of synthetic linear, branched and cyclic alkanes; “proprietary” component • % composition is a trade secret |
| Dustaway | Soilworks | Liquid | • No hazardous ingredients at or above 1%
• No applicable CASRN(s) |
| Dust-Off | Cargill | Salt-based | • Water (63-70%)
• Magnesium chloride (29-33%, CASRN 7786-30-3) • Magnesium sulfate (1-3.8%, CASRN 7487-88-9) • Proprietary corrosion inhibitor (0.02%) |
| Earth Armour | Midwest Industrial Supply | Petroleum-based / synthetic liquid | • Severely hydrotreated paraffinic liquids (100% proprietary mixture) |
| EK-35 | Midwest Industrial Supply | Synthetic liquid | • Tall-oil pitch (<60%, CASRN 8016-81-7)
• Severely hydrotreated, high viscosity, synthetic isoalkane (>10%, CASRN 72623-86-0) • Alkyl polyamines (<4%, proprietary CASRN) |
| Product Name | Manufacturer | Type | Chemical Composition / CASRN |
| EnviroKleen | Midwest Industrial Supply | Synthetic liquid | • Polyolefin (<60%, CASRN 9003-27-4)
• Severely hydrotreated, high viscosity, synthetic isoalkane (>10%, CASRN 72623-86-0) |
| Freedom Binder 400 | Freedom Industries | Organic nonpetroleum-based (tall oil) | • Water (30-60%)
• Tall-oil pitch (30-60%, CASRN 8016-81-7) • Surfactant blend (1-10%, proprietary CASRN) |
| Liquidow | Occidental Chemical Corporation | Salt-based | • Water (53-72%)
• Calcium chloride (28-42%, CASRN 10043-52-4) • Potassium chloride (<3%, CASRN 7447-40-7) • Sodium chloride (<2%, CASRN 7647-14-5) |
| LSP-400 | 3M | Polymer | • Water (44-54%)
• Olefin acrylate polymer (33-39%, proprietary CASRN) • Ammonium alkyl sulfate (2-6%, proprietary CASRN) • Ethyl lactate (1-5%, proprietary CASRN) • Alkyl ester (1-5%, proprietary CASRN) • Sodium alkyl ether sulfate (1-2%, proprietary CASRN) |
| Permazyme
(11X) |
Pacific Enzymes | Enzyme | • Proprietary blend of enzymes |
| Soil Sement | Midwest Industrial Supply | Polymer | • Water (50-95%)
• Acrylic and vinyl acetate polymer (5-50%, non-hazardous) |
| Soiltac | Soilworks | Polymer | • Copolymer of vinyl acetate, ethylene and vinyl ester with mineral fillers and protective colloid liquid product
• Synthetic vinyl copolymer dispersion (55%, non-hazardous) • Water (45%) |
| Top Seal | Soils Control International | Enzyme | • Copolymers, vinyl acrylic, water, and proprietary formulations
• Vinyl acetate (<0.1%, CASRN 108-05-4) |
Data collection involved the following overall steps:
The following subsections describe specific information-gathering activities, which mirrored the overall process followed in 2015 for continuity. Figure 1 highlights each step in the process.
ERG gathered palliative-specific information from various online sources. This process involved searching publicly available databases and websites using a similar assemblage of relevant keywords and search strings developed during the previous effort, but with some refinements based on the targeted nature of this particular follow-on literature search (e.g., documentation published from 2015-present, searching on specific palliatives already known to be used in Alaska). The following search tools were used:
For this effort, the strategy for identifying relevant keywords and keyword search strings focused on the specific palliatives of interest and the desired types of information to collect. The process for each of these is summarized below.
When searching for reference literature, the process involved reviewing abstracts, identifying references most likely to contain relevant information, and obtaining full-text references when possible. Throughout the literature search process, ERG compiled relevant information about each reference in an Excel-based bibliographic database (e.g., author, date, title, URL [if applicable], full citation, and summary notes for the reference).
While some reference materials were available online in their entirety, others were limited to abstracts or brief summaries. To complete the primary literature search, ERG established a tiered approach for reviewing and compiling relevant information, which applied to all documents reviewed under this task order. The process included searching online databases for references potentially relevant to palliatives and project objectives (Step 1), targeting documents that could be useful based on a review of abstracts and other information (Step 2), obtaining and reviewing full references for those deemed relevant (Step 3), summarizing the information contained (Step 4), and flagging whether the references contained information on chemical make-up of palliatives, relative toxicity values, newer regulations or advisories applicable to palliative use and exposure, and any mention of frequency of specific palliative use in Alaska. Toxicity information gleaned from the published literature and the palliative manufacturing SDSs was compiled into a table. Each step of the documentation search process is summarized in Table 2.
| Step | Task |
| 1 | Search online data sources (e.g., Google Scholar, PubMed) using keywords and keyword search strings. |
| 2 | Review abstracts and summary information for each reference. |
| Flag sources of information relevant for project-specific needs. | |
| 3 | If accessible, obtain and review the full reference, and cite and summarize it in the bibliographic database. |
| 4 | Search online data sources to obtain the most current SDS for each palliative. |
| 5 | Populate the bibliographic database with SDS reference information. |
As part of the literature search effort, ERG reached out to manufacturers and a subject matter expert to seek toxicity data for the palliatives with no publicly available toxicity information. No palliative-specific toxicity information was obtained for 5 of the 17 palliatives (Alastac, AlastaSeal, Dust-Off, Freedom Binder 400, and LSP-400) during this process.
This section synthesizes the findings of the targeted literature review effort. ERG conducted more than 150 search queries to obtain relevant information published since the 2015 effort. Using our institutional knowledge and subject matter experience, ERG evaluated the results of these queries in online websites, and identified literature considered relevant in the bibliographic database. Using the targeted search terms and short time frame window (2015-2019), ERG cataloged nine new resources relevant to the topics of interest, with eight marked as relevant to the project scope and requiring a full review. Articles deemed relevant were those that provided information directly related to the project objectives, goals, and research questions (e.g., dealt with palliative toxicity, included details on palliative chemical make-up, specifically referenced the palliatives of interest). ERG deemed articles irrelevant if they fell outside of this scope (e.g., referred to palliative performance, summarized information on dust effects). In searching the literature review summary results from the past effort, ERG identified 16 articles relevant to the current project goals, and these were evaluated for relevant toxicity data. Updated SDSs were located for 6 of the 17 palliatives, with the previously obtained SDSs for the remaining palliatives still the most applicable.
As stated, the goal of this targeted search was to identity information in newer references related to toxicity, chemical make-up of palliatives, newer regulations or advisories applicable to palliative use and exposure, and any mention of frequency of specific palliative use in Alaska. Results are presented in the following subsections by these topics.
Of utmost concern to EPA for this project was identifying toxicity values (human and environmental) to support the ability to conduct a computational evaluation of potential toxicity (discussed in Section 5), and thereby enabling the Agency to address the stated concerns of Alaska Natives about the potential harm from exposures to palliatives used in the state. Table 3 summarizes whether toxicity data were found for each of the 17 palliatives, narrowed down by toxicity data for fish, mammals, plants, invertebrates, and other aquatic species.
|
Product Name |
Available Toxicity Data |
References |
||||
| Fish | Mammals | Plants | Invertebrates | Other Aquatic Species | ||
| Alastac* | Yes | Yes | No | No | No | Apun, LLC, 2009 |
| AlastaSeal | No | No | No | No | No | Apun, LLC, 2010 |
| DirtGlue | Yes | No | No | Yes | No | GeoCHEM, Inc., 2010 |
| Dowflake | Yes | Yes | Yes | Yes | No | Occidental Chemical Corporation, 2016a |
| Durasoil | Yes | No | Yes | Yes | Yes | Soilworks, 2019 |
| Dustaway | No | Yes | No | No | No | Author unknown, 2017 |
| Dust-Off | No | No | No | No | No | Cargill Salt, 2002 |
| Earth Armour | No | Yes | No | No | No | Midwest Industrial Supply, Inc., 2010 |
| EK-35 | Yes | No | No | Yes | No | Midwest Industrial Supply, Inc., 2015a; Midwest Industrial Supply, Inc., 2017 |
| EnviroKleen | Yes | Yes | No | Yes | No | Midwest Industrial Supply, Inc., 2015b; Steevens et al., 2007; TSL, Tri-State Laboratories, 2002 |
| Freedom Binder
400 |
No | No | No | No | No | Freedom Industries, 2009 |
| Liquidow | Yes | Yes | Yes | Yes | No | Occidental Chemical Corporation, 2016b |
| LSP-400 | No | No | No | No | No | 3M, 2010 |
| Permazyme (11X) | No | No | No | Yes | No | Hobe Associates, 2015 |
| Soil Sement | Yes | No | No | Yes | No | Midwest Industrial Supply, Inc., 2015c, 2015d |
| Soiltac | Yes | No | Yes | Yes | Yes | Soilworks, 2018a, 2018b |
| Top Seal | Yes | Yes | No | Yes | Yes | Rocky Mountain Remediation Services, LLC, 1996;
Soils Control International, Inc., 2006 |
*Data identified for Alastac were presented on the product’s SDS to show the toxicity of various lignosulfonates (the chemical composition of this palliative), but are not necessarily specific to this exact palliative formulation.
Cells populated with a “Yes” are those species for which toxicity data were located for a particular palliative. As noted and shown in the table, aquatic toxicity testing data were available for more of the palliatives than mammalian toxicity data. No toxicity data were found for AlastaSeal, Dust-Off, Freedom Binder, and LSP-400. ERG provided the full compilation of specific toxicity data to EPA as a separate deliverable titled “Bibliographic Database and Toxicity Table.”
This targeted literature search identified a few publications that mention chemical constituents in particular palliatives (e.g., sodium chloride, calcium chloride), but did not provide chemical make-up information specific to the 17 palliatives included in EPA’s investigation. The chemical compositions of the 17 dust palliative products and ingredient CASRNs, when available (i.e., are not proprietary ingredients), were identified from their SDSs (see Table 1).
One document obtained during the targeted literature search (Jones, 2017) mentions the topic of regulations or advisories related to palliatives. This report evaluated available guidelines in the United States related to selecting, identifying, and applying various dust palliatives. Jones (2017) reported that the U.S. does not have any official specifications related to chemical-based palliatives but identifies that palliative suppliers must adhere to the Federal Highway Administration requirements for chemical treatments on unpaved roads. These requirements are referred to as “Standard Specifications for the Construction of Roads and Bridges on Federal Highway Projects” (FHWA, 2014). Jones (2017) also states that chemical-based products used on unpaved roads cannot exhibit “the characteristic of toxicity”, per U.S. EPA’s Resource Conservation Recovery Act (RCRA).
ERG’s targeted literature search identified no additional publications that documented frequency of specific palliative use in Alaska beyond what was documented in EPA’s 2015 effort (see EPA, 2016 for more information). EPA did locate one report that summarized a pilot project involving the use of EnviroKleen and Durasoil on sections of road in the Native Village of Ruby. The purpose of this pilot project was to measure PM10 concentrations in ambient air before and after palliative application (ADEC, 2017).
This literature search effort yielded some details related to the targeted topics of interest, but information gaps and research needs remain. The bullets below highlight remaining gaps on the specific topics explored.
The process for selecting the three palliatives for the computational evaluation involved an examination of the literature search findings and consultations with subject matter experts (see Section 4.1.4). The approach used, and the ultimate palliative selection, are summarized in the sections that follow.
To pinpoint the most appropriate three palliatives for inclusion, ERG examined the targeted literature search findings by considering the focused topics summarized in Sections 4.1.1 through 4.1.3 and reaching out to subject matter experts (see Section 4.1.4).
ERG identified the palliative products that had the least toxicity information available from the literature review. The following five products had the least toxicity information available:
ERG identified the palliative products that had the most toxicity information available from the literature review. About the same amount of information was found for the following eight palliatives:
To further inform the selection of three palliatives for the computational evaluation, EPA sought to hone in on the frequency of use in Alaska for the 17 palliatives known to be used in the state. As noted in Section 3.2.4, ERG found no additional information during the 2019 targeted literature search regarding frequency of use of palliatives in Alaska, but EPA did locate one report that documented the pilot testing of Durasoil and EnviroKleen in a single village (ADEC, 2017). As such, ERG considered information documented in the previous report (EPA, 2016) and ADEC, 2017, which is summarized below.
These research findings indicate that salt-based products, specifically calcium chloride, are the main type of product used on unpaved roads managed by the Alaska DOT&PF. Toxicity information on contaminants in salt-based palliatives (calcium chloride, magnesium chloride, and sodium chloride) were identified in published reports obtained during the literature search. Of the salt-based palliatives in Table 1, toxicity information is available for Dowflake and Liquidow (main salt-based component: calcium chloride). No data were found specific to Dust-Off (main salt-based component: magnesium chloride).
To further aid in the selection process, EPA contacted two subject matter experts in palliative use in Alaska: Billy Connor and David Barnes with the University of Alaska Fairbanks – Alaska University Transportation Center. EPA shared the information collected during the targeted literature search and proposed three synthetic palliatives to possibly include in the computational evaluation: Durasoil (manufactured by Soilworks), and EK-35 and EnviroKleen (manufactured by Midwest Industrial Supply). The experts:
Based on this detailed evaluation, EPA ultimately selected three synthetic liquid palliatives to focus on in the computational evaluation of potential toxicity: Durasoil (manufactured by Soilworks), and EK-35 and EnviroKleen (manufactured by Midwest Industrial Supply). EPA selected these palliatives based on the following considerations:
Available information indicates which palliatives were applied to village roads at least once, but the number of times and locations that each type of palliative was used on village roads is still unknown. Using institutional knowledge and input from subject matter experts, EPA was able to identify some of the most commonly used palliatives in Alaska to include in the computational evaluation
This section summarizes the approach, findings for each step of the process, and data gaps/research needs for the computational evaluation of potential palliative toxicity conducted for this project.
Evaluating the potential for human toxicity of these palliatives is limited by the lack of information on specific chemical composition. Each palliative is a chemical mixture composed of a proprietary blend of organic compounds. For example:
The toxicity information that is available for these palliatives is based on testing conducted on the whole product, which helped us understand the potential toxicity of each product as it is intended to be used and applied.
Because we do not know the specific chemical constituents and their properties, ERG was unable to use traditional computational toxicological methods such as quantitative structure activity relationship (QSAR) models for this effort, as they rely on input of a specific chemical structure of a compound. However, ERG was able to employ methods that are similar to QSAR-type approaches, which allow us to draw inferences from a wider range of toxicity data. Using this approach, ERG evaluated the relative toxicity of the three subject palliatives while also presenting results in units (doses) that are familiar to a general population.
Figure 2 shows the main objectives at a high level for the computational evaluation of potential toxicity for the three subject palliatives.
For the first main objective, ERG collected toxicity data for Durasoil, EK-35, and EnviroKleen using online resources and personal communication with the manufacturers (Midwest Industrial Supply and Soilworks). Additional scientific approaches were used to convert the available aquatic toxicity values (available as fish LC50s1) for Durasoil, EK-35, and EnviroKleen to mammal toxicity values (oral rat LD50s2), making them relatable to human exposures.
1 LC50 = concentration that causes death in 50% of tested organisms within a certain time period
2 LD50 = dose expected to cause death in 50% of tested organisms within a certain time period
ERG prepared the following step-by-step process to meet the other three main objectives:
This section provides the findings for each step conducted during the computational evaluation.
ERG compiled all available toxicity data for Durasoil, EK-35, and EnviroKleen that were obtained via online resources and personal communication with manufacturers.3 Based on a review of available information, ERG identified that ecological toxicity tests have been conducted under acute and chronic exposure conditions for all three palliatives as whole products. Table 4 provides all the test results of these studies for two fish species (rainbow trout and fathead minnow), three invertebrates (mysid shrimp, two types of water flea, and earthworms), and bacterium.
Based on the palliative-specific toxicity data shown in Table 4, the most sensitive endpoints varied across palliatives:
3 Data are based on the most current manufacturers’ safety data sheets (SDSs), with more specifics on those toxicity values gleaned from the additional references cited, when available. For Durasoil, based on laboratory data collected over time (and provided to ERG by the manufacturer), testing results reported as IC25s and IC50s were assumed to be based on toxicity growth tests.
| Species | Toxicity Measure | Durasoila | EK-35b,c,d | EnviroKleend,e,f |
| Fish | ||||
| Rainbow Trout (Oncorhynchus mykiss) | 96-hour LC50 (survival) | >2,000 mg/L | 30 mg/L | >1,000 mg/L |
| 96-hour NOEC (survival) | – | – | 1,000 mg/L | |
| 96-hour LOEC (survival) | – | – | >1,000 mg/L | |
| 7-day LC50 (survival) | – | 23 mg/L | >1,000 mg/L | |
| 7-day NOEC (survival) | – | 10 mg/L | 1,000 mg/L | |
| 7-day LOEC (survival) | – | 20 mg/L | >1,000 mg/L | |
| 7-day LC50 (growth/reproduction) | – | > 10 mg/L | >1,000 mg/L | |
| 7-day NOEC (growth/reproduction) | – | 10 mg/L | 1,000 mg/L | |
| 7-day LOEC (growth/reproduction) | – | > 10 mg/L | >1,000 mg/L | |
| Fathead Minnow | 96-hour LC50 (survival) | – | 271 mg/L | >1,000 mg/L |
| (Pimephales promelas) | 96-hour NOEC (survival) | – | 125 mg/L | 1,000 mg/L |
| 96-hour LOEC (survival) | – | 250 mg/L | >1,000 mg/L | |
| 7-day LC50 (survival) | >28,000 mg/L | 97.3 mg/L | >1,000 mg/L | |
| 7-day NOEC (survival) | – | 31.3 mg/L | 1,000 mg/L | |
| 7-day LOEC (survival) | – | 62.5 mg/L | >1,000 mg/L | |
| 7-day LC50 (growth/reproduction) | – | 114 mg/L | >1,000 mg/L | |
| 7-day NOEC (growth/reproduction) | – | 31.3 mg/L | 1,000 mg/L | |
| 7-day LOEC (growth/reproduction) | – | 62.5 mg/L | >1,000 mg/L | |
| 7-day IC25 (growth) | >2,000 mg/L | – | – | |
| 7-day IC50 (growth) | >39,000 mg/L | – | – | |
| Invertebrates | ||||
| Mysid Shrimp (Americamysis bahia) | 96-hr LC50 (survival) | – | 111 mg/L | >1,000 mg/L |
| 96-hr NOEC (survival) | – | 63 mg/L | 1,000 mg/L | |
| 96-hr LOEC (survival) | – | 130 mg/L | >1,000 mg/L | |
| 7-day LC50 (survival) | >2,000 mg/L | 58.6 mg/L | >1,000 mg/L | |
| 7-day NOEC (survival) | – | 25 mg/L | 1,000 mg/L | |
| 7-day LOEC (survival) | – | 50 mg/L | >1,000 mg/L | |
| 7-day LC50 (growth/reproduction) | – | >50 mg/L | >1,000 mg/L | |
| 7-day NOEC (growth/reproduction) | – | 50 mg/L | 1,000 mg/L | |
| 7-day LOEC (growth/reproduction) | – | >50 mg/L | >1,000 mg/L | |
| 7-day IC25 (growth) | >1,000 mg/L | – | – | |
| Water Flea
(Daphnia magna) |
48-hour LC50 (survival) | 18,000 mg/L | – | – |
| Water Flea | 48-hr LC50 (survival) | – | >1,000 mg/L | >1,000 mg/L |
| (Ceriodaphnia dubia) | 48-hr NOEC (survival) | – | 1,000 mg/L | 1,000 mg/L |
| 48-hr LOEC (survival) | – | >1,000 mg/L | >1,000 mg/L | |
| 7-day LC50 (survival) | – | >1,000 mg/L | >1,000 mg/L | |
| 7-day NOEC (survival) | – | 500 mg/L | 1,000 mg/L | |
| 7-day LOEC (survival) | – | 1,000 mg/L | >1,000 mg/L | |
Table 4. Toxicity of Durasoil, EK-35, and EnviroKleen
| Species | Toxicity Measure | Durasoila | EK-35b,c,d | EnviroKleend,e,f |
| Water Flea
(Ceriodaphnia dubia) [continued] |
7-day LC50 (growth/reproduction) | – | 375 mg/L | >1,000 mg/L |
| 7-day NOEC (growth/reproduction) | – | 250 mg/L | 1,000 mg/L | |
| 7-day LOEC (growth/reproduction) | – | 500 mg/L | >1,000 mg/L | |
| Earthworm
(Eisenia andrei) |
14-day LC50 (survival) | >670,000 mg/L | – | – |
| Other | ||||
| Bacterium
(Aliivibrio fischeri) |
15-minute IC50 (growth) | >500,000 mg/L | – | – |
Notes:
“-“ indicates no data are available
IC25 = Point estimate of toxic concentration that would cause a 25% reduction in non-lethal biological measurement
IC50 = Point estimate of toxic concentration that would cause a 50% reduction in non-lethal biological measurement
LC50 = Lethal Concentration, 50%
LOEC = Lowest Observable Effects Concentration mg/L = milligrams per liter
NOEC = No Observable Effects Concentration References:
a Soilworks. 2019. Durasoil safety data sheet. Revised April 2, 2019. https://www.soilworks.com/media/115319/sds1501001-durasoil-safety-data-sheet-en-.pdf. b Midwest Industrial Supply, Inc. 2015. EK35 Series safety data sheet. Revised May 21, 2015. http://midwestind.com/wp-content/uploads/MW_EK35_Series_SDS.pdf.
c Midwest Industrial Supply, Inc. 2017. Environmental data for EK35 synthetic organic dust control. http://midwestind.com/wp-content/uploads/MW_EK35-Environmental-Data.pdf.
d ABC Laboratories, Inc. 2003. Study title: 7-day survival and growth tests of dust suppression products EK-35 and EnviroKleen to the rainbow trout, oncorhynchus mykiss, determined under static removal conditions. Provided by Cheryl Detloff, Midwest Chemist.
e Midwest Industrial Supply, Inc. 2015. EnviroKleen safety data sheet. Revised May 22, 2015. http://midwestind.com/wp-content/uploads/MW_EnviroKleen_SDS.pdf.
f ABC Laboratories. 2002. EnviroKleen environmental data, acute and chronic aquatic toxicity. Provided by Cheryl Detloff, Midwest Chemist.
ERG evaluated all the available toxicity data and identified toxicity endpoints that were consistently measured across the three palliatives for the same given species and duration of exposure (shown in Table 5). These endpoints include the 96-hour LC50 for rainbow trout, 7-day LC50 for the fathead minnow, and 7-day LC50 for the mysid shrimp. An examination of the toxicity data for these specific endpoints indicates that EK-35 is more toxic than Durasoil and EnviroKleen because it consistently has the lowest toxicity value. Of the three common toxicity endpoints, the most sensitive is the 96-hour LC50 for rainbow trout, which indicates that 50% of trout died when exposed to EK-35 at a concentration of 30 mg/L for 96 hours. For EnviroKleen and Durasoil, the 96-hour LC50s for survival were not observed at the maximum concentrations tested and were therefore estimated to be >2,000 mg/L and >1,000 mg/L, respectively. This rainbow trout acute toxicity endpoint, as well as the other two chronic toxicity endpoints (7-day LC50 for fathead minnow and 7-day LC50 for mysid shrimp), suggest that EK-35 has the potential to be more toxic than both Durasoil and EnviroKleen.
| Toxicity Endpoint | Durasoila | EK-35b | EnviroKleenc |
| 96-hour LC50 (survival) for rainbow trout
(Oncorhynchus mykiss) |
>2,000 mg/L | 30 mg/L | >1,000 mg/L |
| 7-day LC50 (survival) for fathead
minnow (Pimephales promelas) |
>28,000 mg/L | 97.3 mg/L | >1,000 mg/L |
| 7-day LC50 (survival) for mysid shrimp
(Americamysis bahia) |
>2,000 mg/L | 58.6 mg/L | >1,000 mg/L |
References:
a Soilworks. 2019. Durasoil safety data sheet. Revised April 2, 2019. https://www.soilworks.com/media/115319/sds1501001-durasoil-safety-data-sheet-en-.pdf. b Midwest Industrial Supply, Inc. 2015. EK35 Series safety data sheet. Revised May 21, 2015. http://midwestind.com/wp-content/uploads/MW_EK35_Series_SDS.pdf.
c Midwest Industrial Supply, Inc. 2015. EnviroKleen safety data sheet. Revised May 22, 2015.
http://midwestind.com/wp-content/uploads/MW_EnviroKleen_Series_SDS.pdf.
There is no clear way to distinguish between the toxicity of Durasoil and EnviroKleen given these data, as LC50s were not observed for both palliatives at the maximum concentrations tested. However, the toxicity tests for Durasoil used a maximum concentration that was greater than the toxicity tests for EnviroKleen, providing evidence to suggest that Durasoil likely has the lower toxicity of the two.
To provide added perspective, Figure 3 compares the toxicity values presented in Table 5 to EPA’s ecotoxicity scale for aquatic organisms (EPA, 2017). Based on this toxicity scale for the three common toxicity measures across the subject palliatives, the aquatic toxicity results presented for Durasoil and EnviroKleen for 96-hour LC50s for rainbow trout, 7-day LC50s for fathead minnow, and 7-day LC50s for mysid shrimp all are at least a factor of 10 greater than 100, indicating they are practically non-toxic to aquatic organisms. The LC50s for EK-35 for these three endpoints ranged from 30 mg/L to 97.3 mg/L, falling within EPA’s slightly toxic range for aquatic toxicity. These toxicity levels mean that Durasoil, EK-35, and EnviroKleen are unlikely to adversely affect the survival of fish in the environment where they would most likely be present at much lower concentrations.
ERG collected information from manufacturers’ SDSs on the ecological toxicity of an array of common household products. The 96-hour LC50s for rainbow trout survival for the three palliatives were then compared to common household products to help put the relative toxicity information into context for a broader audience. Of note, while data for the palliatives were based on whole products, the household data were based on the primary active ingredient of each product. ERG conducted a sweep to locate available toxicity data for a plethora of commonly used household products. Aquatic toxicity data were identified to enable comparisons between products and one endpoint across all three palliatives: 96-hour LC50s for rainbow trout survival. The products included air freshener & deodorizer, bar soap, hand & body lotion, hand sanitizer, no-rinse body wash, and salt. The LC50s for these products are displayed in Table 6.
|
Common Household Product |
Active Ingredient (percent in product, if known) | 96-hour LC50 Rainbow Trout (Oncorhynchus
mykiss) (mg/L) |
| Air Freshener & Deodorizer | Acetone, 60-80% | 4,740-6,330 |
| Bar Soap | Glycerin, 1-10% | 50 |
| Hand & Body Lotion | Glycerol, proprietary percentage | 67,500 |
| Hand Sanitizer | Ethanol, 50-75% | 42 |
| No-rinse Body Wash | Propylene glycol, proprietary percentage | 40,613 |
| Salt | Sodium chloride, 98.5-99.5% | 2,800 |
*Information was obtained from product SDSs.
LC50s presented in the SDSs in the unit of mL/L were converted to mg/L.
Based on this endpoint comparison, EK-35 has a lower LC50 (30 mg/L) and is therefore more toxic than all of the household products listed in Table 6. The evaluative data show that Durasoil and EnviroKleen are less toxic than hand sanitizer and bar soap. However, a judgement cannot be made on the relative toxicity of Durasoil and EnviroKleen compared to the remaining household products because LC50s were not observed at the maximum concentrations tested in these palliative aquatic toxicity assessments (2,000 mg/L and 1,000 mg/L, respectively).
5.2.3. Step 3: Extrapolate Ecological Toxicity Data (LC50s) to Mammalian Toxicity (LD50s) The available toxicity data for each palliative (shown in Table 4) are primarily from studies conducted with fish or invertebrates. No mammalian toxicity data, such as 50% lethal doses (LD50s), were available for the palliatives as whole products. However, methods have been developed to relate LC50s in non-mammalian species to LD50s in mammals (Delistraty et al., 1998; Hodson, 1985; Janardan et al., 1984; Kaiser and Esterby, 1991; Zolotarev et al., 2017). These methods involve developing regression models from a large collection of paired observations of
LC50s, for example in fish, and LD50s in rats from toxicity studies on a wide range of chemicals. Table 7 presents a summary of regression models published in the scientific literature that were developed to relate LC50s in rainbow trout to rat LD50s.
| Reference | Test Chemicals | Na | Y Variableb | X Variableb | Slope | Intercept | rc |
| Janardan et al. 1984 |
Priority Pollutants |
24 |
Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(µmol/L) |
0.35 |
-0.161 |
0.63 |
| Janardan et al. 1984 | Priority pollutants and pesticides
combined |
64 |
Male Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(µmol/L) |
0.33 |
-0.34 |
0.58 |
| Janardan et al. 1984 | Priority pollutants and pesticides
combined |
64 |
Female Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(µmol/L) |
0.36 |
-0.259 |
0.67 |
| Janardan et al. 1984 | Chlorinated pesticides |
12 |
Male Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(µmol/L) |
0.59 |
0.192 |
0.999 |
| Janardan et al. 1984 | Chlorinated pesticides |
12 |
Female Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(µmol/L) |
0.28 |
0.38 |
0.999 |
|
Hodson 1985 |
Phenols, benzenes, anilines, solvents,
misc. |
15 |
Rat LD50
(mmol/kg) |
Trout LC50 (mmol/L) |
0.7086 |
1.6553 |
0.62 |
| Kaiser and Esterby 1991 | Variety of chemical lasses |
91 |
Rat LD50
(mmol/kg) |
Fathead Minnow LC50
(mmol/L) |
0.36 |
-1.16 |
0.583 |
| Delistraty et al.
1998 |
Pesticides and non-
pesticides |
213 | Trout LC50
(mmol/L) |
Rat LD50
(mmol/kg) |
0.722 | -2.16 | 0.512 |
a The number of chemicals used in developing the regression model
b LD50s and LC50s were logged for regression analyses
c Correlation coefficient
mmol/kg = millimoles per kilogram µmol/L = micromoles per liter
The regression models in Table 7 were based on data from individual chemicals with known properties, and the models are often improved by including these properties as covariates. For example, a compound’s octanol-water partition coefficient (lgP or logKow) has been established as an important covariate in predicting a mammalian LD50 from a fish LC50. This is because the partition coefficient is a measure of hydrophobicity, and very hydrophobic compounds tend to accumulate in fish to a much greater degree than in mammals.
An additional limitation of the regression models presented in Table 7 is that they were fit to data in molar units. Because toxicological effects occur at the molecular level, molar units are most appropriate when comparing toxicities of different compounds. However, without knowing the constituent composition of each palliative, ERG did not know the molecular weight of each compound within each palliative, which meant we are unable to use the regression equations from Table 7 directly. Instead, we used a similar approach and developed a regression model based on the units of the available toxicity data, mg/L (as opposed to molar units).
ERG developed two regression models that predict mammalian toxicity (LD50s) using the available LC50 fish toxicity data from Table 5 for the three subject dust palliatives. The two regression models were based on data sets from two studies that included paired fish LC50s and rat LD50s. The steps for developing these models were as follows:
The fact that these two models were significant demonstrates that there is an association between fish LC50s and rat LD50s. This allowed ERG to extrapolate from the limited toxicity data available for each palliative. Keeping in mind that the correlation from these models was not large, we could still form a first order approximation.
Therefore, the regression equations from each model were used to extrapolate LD50s for the two fish endpoints (96- hour survival LC50s for rainbow trout and 7-day survival LC50s for fathead minnow) from Table 8. Of note, the shrimp toxicity values were not used to predict LD50s because the two data sets used in developing the regression models were based on fish toxicity data.
Table 8 shows the predicted rat LD50s that result from applying these models to the toxicity data for the three palliatives.
| Model | Toxicity Endpoint | Durasoila | EK-35b | EnviroKleenc |
|
Model based on Zolotarev et al. 2017 data |
Rat LD50 (extrapolated from 96- hour LC50 for rainbow trout) | >3,409 | 1,060 | >2,811 |
| Rat LD50 (extrapolated from 7-day
LC50 for fathead minnow) |
>7,104 | 1,470 | >2,811 | |
|
Model based on Hodson 1985 data |
Rat LD50 (extrapolated from 96-
hour LC50 for rainbow trout) |
>5,351 | 1,136 | >4,143 |
| Rat LD50 (extrapolated from 7-day
LC50 for fathead minnow) |
>14,173 | 1,753 | >4,143 |
The two models produced surprisingly similar results. This can be seen when comparing the regression equations above, or by looking at the range of predicted LD50 values for EnviroKleen, which had the same LC50 inputs for both rainbow trout and fathead minnow of >1,000 mg/kg. The two models produced predicted LD50s that ranged from >2,811 to >4,143 mg/kg, a factor difference of approximately 1.5. Still, the predicted mammalian toxicity values in Table 8 vary depending on which regression model and LC50 input were used. The variation seen in predicted LD50s is greatest for Durasoil, primarily because the input values for this palliative had the greatest range (from >2,000 mg/kg for the 96-hour LC50 for rainbow trout to >28,000 mg/kg for the 7-day LC50 for fathead minnow). The predicted LD50 values for EK-35 had the smallest range from 1,060 mg/kg to 1,753 mg/kg.
Because the Hodson model was developed from rainbow trout toxicity data, an argument can be made that this is the more appropriate model to use when extrapolating from a rainbow trout LC50. The Zolotarev et al. (2017) model was based on zebra fish data but was developed from a much larger number of chemicals and conducted more recently. Neither model used fathead minnow data, however.
While no mammalian toxicity data were available for the palliatives as whole products, for the EnviroKleen palliative only, ERG was able to obtain LD50 toxicity on its two chemical constituents. Those data are presented here to offer additional perspective. LD50s were available for two different raw materials that make up EnviroKleen: polyolefin and a synthetic isoalkane. The synthetic fluid had a rat oral LD50 >5,000 mg/kg, and polyolefin (polyisobutylene) had a rat oral LD50 >5,000 mg/kg. Thus, while the available LD50s are not representative of mammalian toxicity on the full palliative composition, these two materials make up 100% of EnviroKleen at proprietary proportions and therefore are good indicators of the potential toxicity of the palliative. The LD50 values here are consistent with the predicted values presented in Table 8.
In the previous Step 2, ERG compared 96-hour LC50s in rainbow trout between the three subject palliatives and a variety of common household products. In Step 4, ERG compared the predicted oral rat LD50s for the three palliatives to oral rat LD50s for the same products as in Step 2, as well as a few additional common household products for which only LD50s were available (see Table 9). While Step 2 involved comparing LC50s for the palliatives to common household products, this LD50 comparison was performed because an LD50 dose is an easier to understand toxicity metric for humans than an LC50, which is an aquatic toxicity concentration. The findings of this comparison are presented below:
It is worth noting that Durasoil and EnviroKleen are more difficult to assess because the extrapolated LD50s are based on their LC50s, for which ERG only knew that their toxicity was above a certain tested maximum concentration. However, as summarized above, we can more confidently speak to the household product LD50s that fall within the predicted LD50 ranges for the palliatives and to those below those ranges.
| Common Household Product | Active Ingredient | Oral LD50 Rat (mg/kg) |
| Air Freshener & Deodorizer | Acetone, 60-80% | 5,800 |
| Antiperspirant/Deodorant Spray | Propylene glycol, 3-7% | 20,000 |
| Aspirin | Acetylsalicylic acid, 100% | 1,500 |
| Baby Foaming Shampoo & Wash | Mixture of ingredients | >5,000 |
| Bar Soap | Glycerin, 1-10% | 12,600 |
| Bug Spray (mixture of ingredients) | Mixture of ingredients | 1,747 |
| Hand & Body Lotion | Glycerol, proprietary percentage | 12,600 |
| Hand Sanitizer | Ethanol, 50-75% | 7,060 |
| Liquid Laundry Detergent | Caustic potash, 45% | 333 |
| No-rinse Body Wash | Propylene glycol, proprietary
percentage |
20,000 |
| Salt | Sodium chloride, 98.5-99.5% | >3,000 |
The toxicity of each substance can further be interpreted by converting the extrapolated mammalian doses (LD50s) into human equivalent doses (HEDs) based on allometric equations, which relate body weight and surface area between species. This method is commonly used in risk assessments, for example in deriving oral reference doses, and allows for an easier to understand metric of toxicity in terms of human exposure (EPA, 2010).
The EPA-recommended equation for calculating an HED is: Laboratory animal exposure (mg/kg) x DAF = HED (mg/kg), where DAF is the Dosimetric Adjustment Factor, a factor that relates the body weight of the test animal to that of the human. For rats, the recommended DAF is 0.24. To account for interspecies variability, an uncertainty factor of 3 is also applied. Table 10 shows the calculated HEDs derived from the predicted LD50s.
| Model | Toxicity Endpoint | Durasoil | EK-35 | EnviroKleen |
| Model based on Zolotarev et al. 2017 data | Rat LD50 (extrapolated from
96-hour LC50 for rainbow trout) |
>273 | 85 | >225 |
| Rat LD50 (extrapolated from 7- day LC50 for fathead minnow) | >568 | 118 | >225 | |
| Model based on Hodson 1985 data | Rat LD50 (extrapolated from
96-hour LC50 for rainbow trout) |
>428 | 91 | >331 |
| Rat LD50 (extrapolated from 7- day LC50 for fathead minnow) | >1,134 | 140 | >331 |
To better understand the toxicity of the predicted LD50s for humans, ERG compared the estimated range of predicted palliative LD50s (Durasoil: >3,409 to >14,173 mg/kg, EK-35: 1,060 to 1,753 mg/kg, and EnviroKleen: >2,811 to >4,143 mg/kg) to the established Hodge and Sterner (1943) toxicity scale (see
Figure 6 and Table 11). This scale rates toxicity from extremely toxic to relatively harmless using a total of four levels in between (for a total of six). Based on that scale, EK-35 is classified as slightly toxic, corresponding to a probable lethal dose in humans of ingesting approximately a pint. While precise estimates of LD50 for Durasoil and EnviroKleen are not available, at their most toxic estimate (the lowest predicted LD50), EnviroKleen would also be classified as slightly toxic, whereas Durasoil would be either classified as slightly toxic or practically non-toxic depending on which model estimate was used. A practically non-toxic classification would correspond to a probable lethal dose in humans of ingesting a quart. The actual toxicity of Durasoil and EnviroKleen, however, is not truly known and predictions are limited by the available toxicity data.
|
Toxicity Rating |
Commonly Used Term |
Oral Rat LD50 Scale Range in mg/kg |
Predicted LD50s in mg/kg (from Table 8) |
Probable Lethal Dose in Humans |
|||
| Durasoil* | EK-35 | EnviroKleen* | |||||
| 1 | Extremely Toxic | 1 or less | 1 grain (a taste, a drop) | ||||
| 2 | Highly Toxic | 1-50 | 4 mL (1 tsp) | ||||
| 3 | Moderately Toxic | 50-500 | 30 mL (1 fl. oz.) | ||||
| 4 | Slightly Toxic | 500-5,000 | >3,409 to
>14,173 |
1,060 to
1,753 |
>2,811
to >4,143 |
600 mL (1 pint) | |
| 5 | Practically Non-toxic | 5,000-15,000 | 1 liter (or 1 quart) | ||||
| 6 | Relatively Harmless | 15,000 or more | 1 liter (or 1 quart) | ||||
*Toxicity values for Durasoil and EnviroKleen represent lower bounds and could be larger (less toxic) than the values reported here.
The Hodge and Sterner scale is referenced in various sources, such as https://www.ccohs.ca/oshanswers/chemicals/ld50.html.
5.2.7. Computational Evaluation Conclusions
The approach described herein allowed ERG to put the limited available aquatic toxicity data for three subject palliatives into perspective in terms of relative toxicity and human exposure. Based on our extrapolations, these three palliatives fall into the “slightly toxic” to “practically non-toxic” categories for human exposure using an established toxicity scale. Using this established toxicity scale, it is estimated that there is a 50% chance of death for humans who consumed 1 pint (slightly toxic) to 1 quart (practically non-toxic) of pure palliative product. In the environment, they are greatly diluted. It is unlikely that subsistence foods near roads would be a conduit for ingesting this much of the palliative product. For example, the LC50s for fish would not be of concern to Alaska Native people because even if palliatives were to runoff into nearby water bodies, they would be greatly diluted.
All numerical values are LD50s in units of milligrams per kilogram (mg/kg).
*Toxicity values for Durasoil and EnviroKleen represent lower bounds and could be larger (less toxic) than the values reported here. The extrapolated LD50s are based on their LC50s, for which it is only known that their toxicity is above a certain tested maximum concentration, which is why “>” symbols are applied to the ranges. Durasoil falls into two categories, based on its wide range of predicted LD50s.
The Hodge and Sterner scale is referenced in various sources, such as https://www.ccohs.ca/oshanswers/chemicals/ld50.html.
Overall, EK-35 was found to be the most toxic of the three palliatives. Because LC50s were not observed at the maximum concentrations tested for Durasoil and EnviroKleen, ERG cannot definitively say which of the two palliatives is more toxic. However, based on the maximum concentrations tested during toxicity assessments, there is evidence to suggest that Durasoil likely has a lower toxicity than EnviroKleen. To give an idea of how comparatively toxic the palliatives are, the established Hodge and Sterner Toxicity Scale was used to compare the predicted palliative LD50s to LD50s for household products.(Figure 6). Specifically,
This comparative analysis between the estimated toxicity of these three palliatives and common household products shows that Durasoil and EnviroKleen in their pure, undiluted form are not more toxic than many commonly used household items.
As with all scientific approaches of this nature, there are some limitations that need to be acknowledged with the computational evaluation of potential toxicity. The identified limitations include the following:
To address some of these limitations, additional toxicity data for these palliatives is desired. Specifically, studies should evaluate the toxicity of these palliatives to mammals at endpoints beyond lethality. This additional data would provide for a more direct evaluation of the potential toxicity of these three palliatives to humans. Moreover, having the actual levels at which certain endpoints occur for Durasoil and EnviroKleen would allow for calculating actual estimates of toxicity, rather than needing to use the available upper bound data based on the maximum concentrations tested.
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