Comments on Toxicity & Environmental Transport of Boron at Site (Related Documents Attached)
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iiiiiiiiiiiiiiiiiiiiiiiiiiiliiiiiiiiiiliiiii ,.^tOS7-4 V_ SDMS DocID 2139527 >'^'j-,J^<«> UNITED STATES ENVIRONMENTAL PROTECTION AGENCY #5>' _J^S^ \ REGION III I N^i^ g 1650 Arch Street V**"''* .^ Philadelphia, Pennsylvania 19103-2029 "•t PRCft*-*^ September 4, 2009
SUBJECT: Toxicity and Environmental Transport of Boron at the Salford Quarry Site
TO: File
FROM: Lorie BakeffrJPL Coordinator, Site Assessment and Non-NPL Federal Facilities Branch (3HS12)
This memorandum discusses the toxicity of boron and the evidence that is available to date regarding the transport of boron from the Salford Quarry to nearby residential wells. EPA proposed the site to the NPL in 1997, using the revised HRS rule which was promulgated in 1990.
in accordance with Section 2.4.1. of the HRS Rule, the hazardous substance potentially posing the greatest hazard for the pathway is used to evaluate the waste characteristics category of the pathway. Since only the ground water pathway was scored for this site, toxicity and mobility factors, along v^th waste quantity, are considered. See HRS Section 3.2. Boron is the contaminant of concern, and EPA used the most toxic form of boron present at the site, boric acid, to calculate toxicity values. Although boron was disposed at this site in the form of boric oxide, scientific literature indicates that, following contact with water, and depending upon the pH of the water, boric oxide will convert to either borates or boric acid in the envirorunent (Attachment 1 and HRS Ref 94). Generally the standard analysis for boron in water samples will produce results of "total" boron. This means that the boron can be associated with a combination of various boron compounds. The literature suggests that most boron found in aqueous solufion is in the form of either boric acid or borates, and not boric oxide (Attachment 1 and HRS Refs. 94, 100). In solution, borates and boric acid establish equilibrium with the exact proportion of each form controlled by pH. Acidic conditions favor boric acid, and basic conditions favor borates. (Attachment 1 and HRS Refs. 94,100) Thus, at least some portion of the release can be expected to consist of boric acid. When these compounds are ingested with drinking water, they would be expected to fully convert to boric acid due to the extremely acidic conditions in the stomach (Attachment 1 and HRS Ref 100).
Although boric acid is the most toxic form of boron, the HRS only assigns a toxicity value of 100 out of a possible 10,000. This value is derived from an inhalation' reference concentration (RfC) of 2E mg/m (from EPA's HE AST database) which then is converted to an
i As explained in Recalculation of HRS Score Using Updated Benchmark Values for Boron, the inhalation value is used because it results in the highest toxicity factor value, as specified in the HRS.
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inhalation reference dose (RfD) of 5.71 E'^ mg/kg/day in accordance with Superfund risk assessment guidance. This RfD is in the range of 0.005 to 0.05 mg/kg/day which is assigned a value of 100 for toxicity (See HRS Rule Section 2.4.1.1 and Table 2-4). This is the value that was used in the 1997 proposed HRS score. The toxicity value has not changed since 1997. The revised HRS model also requires consideration of a mobility factor in scoring the ground water pathway [HRS Rule Section 3.2.1.2]. The highest mobility factor of "1" was assigned to the scoring of the site, because EPA established an observed release by chemical analysis. (See HRS Section 3.2.1.2). Therefore the combined toxicity/mobility for Salford under the proposed model is 100 out of a potential 10,000.
With regard to the migration of boron from the Salford Quarry, a remedial investigation (RI) of the site was completed in 2007. There now are nimierous monitoring wells onsite and downgradient of the site which were installed to determine the extent and migration direction of containination. The RI report will be placed in administrative record for Salford Quarry for the NPL listing. Results from these monitoring wells show boron concentrations that have remained consistently high throughout years of monitoring. The EPA Region III risk-basedscreenin g concentration (RBC) for boron is 7,300 ug/l. Because of the additive effects of noncarcinogenic compounds, the Regional protocol is to use 0.1 of the RBC to establish screening values. Available data suggests that a boron plume with concentrations above the screening value of 730 ug/L has migrated approximately 1.4 miles southwest of the site. The migration of this contaminant plume from the quarry can be traced along the northeast-southwest strike of the Lockatong and Brunswick Formations to several downgradient residential Wells The background levels of boron in the area are low to non-detect, so there is clearly evidence that the boron plume is coming fromth e quarry. (EPA Remedial Investigation, 2007)
In summary, the toxicity and mobility factor values at this site, as calculated in accordance with the HRS Rule, would result in an HRS score that would support listing. In addition, boron can be positively linked to the quarry based on information presented in the proposed HRS package and on supplemental information from the 2007 RI.
Attachments
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Karl To Lorie Baker/R3/USEPA/US@EPA MarWe«vlcz/R3/i;SEPA/US 06/11/200i»H«iuwwiuBn*wocr/vuj9 03:05 PM , ^ Lore Wemer/R3AJSEPArtJS@EPA bcc SutJject Re: Fw: Re: Fw: Boron (Gas Numt>er 007440-42-8)Q
History: ^ This message has been replied to and forwarded.
Hello Lorie,
Regarding boric oxide, the scientific literature indicates that it reverts to boric acid in the environment (and body) following contact with water.
Boron is a trace eletnent and Is not metabolized In the human body. Borates exist in the body as boric add, the only form of boron recoveired in the urine. Boron predominately exists in soil and water as boric acid and borates.
In 2004, EPA revised the RfD for boron and the resulting drinking water comparison values (CVs) for adults and children were increased accordingly (adult = 6,000 ppb (2,100 ppb prior value); children 2,450 ppb (800 ppb prior value)). ATSDR concurs with EPA's ctironic oral RfD for boron regarding public health protectiveness.
In 2007, ATSDR established an intermediate oral MRL for boron of 0.2 mg/kg/day based on the combined Price, et al. 1996 and Heindel, et al.1992 data for devetopmental effects, using the beiichmark dose approach and applying chemical specific adjustment factors. A chronic oral MRL would not be derived because the highest NOAEL for reproductive effects in a 2-year rat study (Weir and Fisher 1972) is higher than the LOAEL used in deriving the intennedlate oral MRL. Thus the intermediate oral MRL is protective of chronic oral exposures. As such, ATSDR's intermediate drinking water CVs are 2,000 ppb for children and 7,000 ppb for adults.
Considering the toxicologic Information at>ove, data indicating that on-site and off-site boron levels in groundwater wells (some former resklential wells) are above CVs, the potential for plume migicition, and uncontrolled source area, ATSDR supports actions to mitigate potential exposures to impacted groundwater.
From ATSDR's 2007 Boron Tox Profile:
3.2.2 Oral Exposure Data for boron oral toxicity in humans involves exposure to the borates or boric acid. These l)oron-containing compounds are primarily found in food and water and have been implicated in numerous accidental or Intentional poisonings in human case reports. Similarly, the boron toxicity studies in animals have utlliz(9d exposures'to borates or boric acid.
6.3.2.2 Water
As an element t>oron Itself cannot t>e degraded in the environment; however, it may undergo various reacttons that change tt>e form of boron (e.g., precipitation, polymerization, and acid-base reactions) depertding on conditions such as its concentration in water and pH. In nature, boron in generally found iri its oxygenated form (Cotton et al. 1999). In aqueous solution, boron is normally present as boric acid and borate tons, with the dominant form of Inorgank: boron in natural aqueous systems as undissociated boric acid (Choi and Chen 1979). Boric acid acts as an electron acceptor In aqueous solution, accepting an hydroxide ion from water to form (B(OH)4)-k)n. In dilute solution, the favored form of boron is Bi[OH>4(Cotton et al. 1999). In more concentrated solutions (>0.1 M boric acid) and at neutral to alkaline pH (6-11), polymeric species are formed (e.g., B303(OH)4-, B506(OH)4-,
AR100710 B303(OH)52-, and B405(OH)42-) (Choi and Chen 1979; Cotton et al. 1999).
6.3.2.3 Sediment and Soil
Most boron compounds are transfbnmed tp borates in soil due to the presence of moisture. Borates themselves are not further degraded In soil. However, borates can exist in a variety of forms ih soil (see Sectton 6.2.3). Borates are removed from soils by water leaching and by assimilatkin by plants
Sincerely,
Kari
KariV.Mariciewicz, PhO Senior Toxkx>loglst HHS/CDC/ATSDR 1650 Arch Street, 3HS00 Philadelphia, PA 19103-2029 215/814-3149 (office) 215/814-3003 (FAX) [email protected]
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TELEPHONE CONVERSATION RECORD
Subject: Salford Quany site (PA-0379) Chemistry of boron compounds Date: 8/11/94 Time: 10:45 A.M.: 2:00 P.M. From: Kevin Wood. NPLTHRS Coordinator, EPA Regton III, Site Assessment Section Phone: (215)597-1110 To: Ted Martin, Research Chemist, EPA EMSL, Cincinnati Phone: (513-569-7312)
I called Mr. Martin to confinm and obtain Infomnation at>out the chemisty of boron compounds. Mr. Martin consulted several publications. Including the Merck Index and Lang's Handbook, as well as some colleagues. Mr. Martin indicated that boric oxide (BgO,; a)solubilities. Boric add Is a weak ackj and tends to retain its hydrogen atoms (pH » 5.1; pK,s at 20^*0 => 9.14, 12.74, and 13.80), and is extremely soluble in cold/ambient water (1 g in 18 mi). The boron detected in.Mj^ered (dissolved metals) samples would be from boric acid and possibly other boron compounds, but not from boric oxida
Mr. Martin also cited a study done at EMSL of surface water samples from around the country. Ninety-eight percent of the samples contained some t>oron, and tiie range was from 1 to 5,000 ppb, with a mean of 101 ppb. These values could be biased high If borosilicate glassware was used.
Mr. Martin suggested performing a literature search arxj/or contacting companies in tiie borax/borate manufacturing sector to obtain more specific Information about the tote of boron in the natural environment
[Note: Pat Suslnstd of the Central Regional Laboratory provided me witii much of the same information on 08/10/94.]
Date: August 11, 1994 Signature: 4\/'o^
AR100712 >^')> UNfFED STATES ENVIRONMENTAL PROTECTION AQENCY \ Region III I 841 Chestnut Street w Philadelphia, Pennsytvania 19107 February 16, 1995
SUBJECT: Toxidty and speciation of environmental boron: Salford Qtiairy site
FROM: Roy L. Smith, Ph.D., Senior Toxicologist Technical Support Section (3HW13) ^^~V^ TO: Kevin J. Wood (3HW73)
As requested, the following infomnation and arguments were used to determine that boron in well water constitutes a potentially significant health risk at the Salford Quarry site.
Borrni is a metalloid element found in rock as a variety of chemical forms; including borides, boates, boranes, organoboron compounds, boron trihalides, borm oxides, and borazines. B Because of the chemistry of boron, the dominant environmental forms to which humans are exposed are borate and boric add. Borate and boric add ingested with drinking water, the medium of concern at Salford (Quarry, would be expected to be fully oonverted to boric add by tiie extremdy acidic conditions (pH between 2 and 3) in the human stomach. The intenal ejqxisure would therefore be to boric add. For this reason there is no toxicological difference between borate and boric add exposure. Exposure to otter boron coinpounds such as boron trihalides is possible under spedal circumstances such as direct occupational contact Boron trihalides are extremely reactive, corrosive, and toxic. Toxicological constants developed for boric add wUl dearly underesthnate health ri^ from boron trihalide exposure. However, such exposure is relativdy rare and cspocMLy unUkdy outside the workplace. Boron trihalides released from industrial qperatiou are quiddy, even explosivdy,;hydrolyzed to borate and boric add.- Because most environmental bonxL exists as borate or b(mc add and internal exposures involve boric add exdusivdy, most investigators of boron toxicology have used boric add as AR100713 tiie source of boron (tiiough some have repotted doses in terms of a sodium borate/ boric add mixtiire). The study on which EPA's oral reference dose was based (Weir et al., 1972) exposed dogs to a sodium borate/ boric add mixture. At high doses die dogs suffered severe atrophy of die testicles and cessation of sperm production. The highest dose at which no effect was observed was 8.8 mg boron per kg body wdght per day. Using 10-fbld uncertainty tictors to account for inter- and intraspedes variability, EPA used tiiis no-observed-effect level to derive a reference dose of 0.09 mg boron per kg body weight per day. Acc^table drinking water concentrations of boron were calculated from diis referoice dose under standard assumptions of body wdghts and t^ water ingestion rates for children and adults. The IRIS file explaining tiie derivation of die refierence dose is attached. The drinking water concentration calculatixxis are already a matter of public record. Please let me know if I can provide further assistance with this site. Attachments I AR100714 52 FOTESTIAL FOR HUHAM EXPOSURE Che discrepancy in Che daca is necessary in ordar CO cenpare boron levels ac hazardous vasce sices co backgroimd levels. S. 3 EHVXBONMERTAL FATE 5.3.1 Transport and Parcicionlng Boron is a nonvolacile necalloid chac occurs in eonbinacion viCh mosc of Che ocher eleoencs Icnomi (Coccon and Vilkinson 1980). ACnospharic boron aay be in chei fora of parciculace maccar or aerosols as borides, boron oxides, boraces, boranes, organoboron coopounds, trihalide boron coopotmds, or borazines. Boraces are relatively soluble.in water, and will probably be reoovad from the acmosphere by preeiplcacion and dry deposition (EFA 1987c). The half-life of airborne parcieles is usually on cha order of days, depending, on Che size of cha particle and atmospheric condicions (Kriagu 1979). No specific inforaacion on che face of acmospheric boron was locaced. Boron readily bydrolyzes in wacer co form the electrically neutral, i#«ak monobasic acid H,BO, and the monovalent ion B(0H)4. In concentrated solutions, boron mxf polymerize, leading to tJie formation of complex and diverse molecular arrangements. Ral et al. (1986) concluded that because most environmentally relevant^ boron minerals are highly soluble in tmter, it is . unlikely that mineral equilibria will control the fate of boron in water. Vaggott (1969), for example, noted that boron is not significantly removed during the conventional treatment of waste water. Boron may, however, be co-precipitated witJi aluminum, silicon, or iron to form hydroxyborate compounds on the surfaces of minerals (Biggar and Fireman 1960). Water borne boron may be adsorbed by soils and sediments. Adsorption- desorption reactions are expected to be the only significant mechanism that will influence the fate of boron in water (Rj^etal. 1986); The extent of boron adsorption depends on the pH of the water and the chemical composition of the soil. The greatest adsorption is generally observed at pH 7.5-9.0 (Keren et al. 1981; Karen and Mezuman 1981; Vaggott 1969). Bingham et al. (1971) concluded diac the single most important property of soil that will influence the mobility of boron is the abundance of amorphous aluminum oxide. The extent of boron adsorption has also been attributed to the levels of'iron oxide (Sakata 1987), and to a lesser extent, the organic matter present in the soil (Parks and Vhite 1952), although other studies (Kesuman and Karen 1981) found that the arrant of organic matter present was not important. The adsorption of boron m^ not be reversible in scma soils. The lack of reversibility m^ be the result of solid-phase formation on mineral surfaces (Ral et al. 1986), and/or the slow release of boron by diffusion from the interior of clay minerals (Griffin and Burau 1974). Partition coefficients such as. adsorption constants describe the tendency of a chemical to partition from water to solid phases. Adsorption constontB for inorganic constituents such as a boron cannot be predicted a priori, but muse be measured for each soil-water eoiAination. C^q>ilations of .e;AP nrmnnnn AR100715 53 5. POTENTIAL FOR HUMAN EXPOSURE available data for borott are given elsewhere (Rai et al. 1986). In general, boron adsorption will be most significant in soils that contain high concentrations of amorphous aluminum and iron oxides and hydroxides such as the reddish Ultisols in the southeastern United States. It is unlikely that boron is bioeoneentrated significantly by organisms from water. A. bioeoneentration factor (BGF) relators the concentration of a chemical in the tissues of aquatic and terrestrial animals or plants to the concentration of the chemical in water or soil. The BCFs of boron in marine and freshwater plants, fish, and invertebrates were estimated to be less than 100 (Thompson et al. 1972). Experimentally measured BCFs for fish have ranged from 52 to 198 (Tsui and MeCart 1981). These BCFs suggest that boron is not significantly bioeoneentrated. Boron in water is completely absorbed by the human system, but it does not accumulate in body tiss«ies (Vaggott 1969). No other experimentally measured BCFs Were located. 5.9.2 Trastfformation and Degradation 5.3.2.1 Aiz There is no information available that suggests that particulate boron compounds are transformed or degraded in the atmosphere. 5.3.2.2 Vater Elemental boron is inert in the presence of water. Boron compounds rapidly transform to borates, the naturally occurring form of boron, in the presence of water. No further degradation is possible. Borate and boric acid are in equilibrium depending only on the pH of the water. If dissolved in atmospheric water, the standard borate-boric acid equilibria are established. 5.3.2.3 Soil Me«t boron compounds are transformed to borates in soil due to the presence of moisture. Borates themselves are not further degraded in soil. However, borates can exist in a variety of forms in soil (see Section 5.2.3). Borates are removed from soils by water leaching and Ij assimilation by plants. 5.4 LEVELS HOHZTOSBII OR ESTZHAXED IB THE ENVXRONMENT 5.4.1 Air There are few studies made to estimate the concentration of boron- containing compounds in ambient air. This is partly due to difficulties of analysis at the low levels involved. Bertine and Goldberg (1971) estimated that approximately 11,600 tons of boron are injected into this a.taosphere as a component of fly ash produced by cool combustion which was estimated to contain an everage of about 75 mg/kg boron. CAC Anonf%4/\ AR100716