------- ------- BORON TABLE OF CONTENTS Page FOREWORD 1-1 I. BORDN INDUSTRY IN THE UNITED STATES 1-2 A. Producers and Sites 1-2 B. Costs and Physical Properties of Important Boron Conpounds 1-12 II. PRODUCTION 1-16 A. Natural Sources of Borates 1-16 B. Manufacturing Processes 1-16 1. Elenental Boron 1-16 2. Borax 1-19 a. The Mining Process 1-19 b. Trona Process 1-21 3. Anhydrous Borax 1-21 4. Boric Acid 1-21 5. Boric Oxide (BaOa, boron trioxide) 1-24 6. Boron Trifluoride (BFs) 1-24 7. Boron Trichloride 1-24 8. Diborane and Higher Boranes (Pentaborane, etc.) 1-24 9. Refractory boron compounds (metal borides, boron carbide, and boron nitride) 1-27 III. USES OF BORON COMPOUNDS 1-28 A. Uses of Boron Conpounds 1-28 B. Future and Potential Uses 1-34 IV. CURRENT PRACTICES 1-35 V. ENVIRONMENTAL CONTAMINATION 1-37 A. From Uses 1-37 1. Emissions to the Atmosphere (including from production) 1-39 2. Amount Entering Waters and Earth 1-40 B. Frcm Production 1-40 1. Mining „ 1-40 2. Processing 1-40 C. Inadvertent 1-41 D. Total Amounts Entering Environment per Year ... 1-41 i. ------- BORON TABLE OF CONTENTS (Can't) Page VI. MONITORING AND ANALYSIS 1-43 A. Monitoring 1-43 B. Analysis. 1-43 1. Determination of Boron in Water ........ 1-43 2. Determination of Boron in Plants and Biological Materials 1-43 3. Analysis of Available Boron in Soil ...... 1-44 4. Detection of Boron in Airborne Contaminants Collected in Air Filters 1-44 5. Analysis of Boron in Air by Colorimetry . . . . 1-44 VII. CHEMICAL REACTIVITY 1-45 A. Environmental and Use Associated Reactions .... 1-45 B. Aspects with Biological Inplication 1-45 VIII. BIOLOGY A. Absorption, Excretion, Growth, and Nutrition. . . . 1-48 1. Humans 1-48 2. Nonhuman Mammals 1-48 3. Plants 1-49 4. Microorganisms 1-51 B. Biochemistry 1-51 1. Humans 1-51 2. Nonhuman Mammals 1-53 3. Nonmammalian Vertebrates 1-56 4. Plants 1-56 5. Microorganisms 1-58 C. Therapeutic Uses 1-59 1. Humans 1-59 2. Nonhuman Mammals 1-60 3. Plants 1-60 IX. ENVIRONMENTAL EFFECTS 1-62 A. Environmental Content, Transport, Contamination . . 1-62 B. Bioaccumulation and Content 1-64 1. Human 1-64 2. Mammals 1-65 3. Plants . 1-65 11. ------- BORON TABLE OF CONTENTS (Can't) Page X. TOXICITY 1-66 A. Humans 1-66 1. Acute Toxicity 1-66 2. Chronic Toxicity 1-67 B. Mammals 1-68 1. Acute Toxicity 1-68 2. Chronic Toxicity 1-69 3. Teratogenicity 1-72 4. Allergic Reactions and Sensitization 1-73 5. Behavioral Effects 1-73 6. Carcinogenicity 1-73 C. Nonmanmalian Vertebrates 1-73 D. Invertebrates 1-74 E. Plants 1-77 F. Microorganisitis 1-84 G. Results of Personal Contacts with Medical Personnel 1-84 XI. CURRENT REGULATIONS AND EFFECTS LEVELS . 1-86 A. Toxicity Levels 1-86 B. Transportation and Handling Regulations 1-86 C. Foreign Regulations 1-87 XII. STANDARDS 1-88 XIII. SUMMARY AND CONCLUSIONS 1-89 A. Summary 1-89 B. Conclusions 1-90 C. Reocmrnendations 1-90 111. ------- KR/AR INC. BORON UST OF TABLES Page 1. Products and Producers . 1-2 2. Prices of Boron Minerals and Chemicals 1-13 3. Physical Properties 1-14 4. Production of Borates in the United States as of 1972 . . . 1-18 5. Uses 1-30 6. Emission Factors 1-38 7. Boron Emissions by Source, 1972 1-38 8. Relative Stabilities of Boron Hydrides 1-46 9. Diagnostic Criteria for Boron Nutrition of Field and Vegetable Crops Based upon Hot Water Extraction of Soil Boron . . . 1-50 .10. Toxic Boron Concentrations of Saturation Extracts for Sensitiw, Semitolerant Crop Species 1-78 11. Plant Growth as Affected by Boron 1-79 12. Symptoms of Boron Toxicity 1-82 IV. ------- BORON LIST OF FIGURES Page 1. Location of Borate (deposits in California, Nevada and Oregon . 1-17 2. Borax production from ore . 1-20 3. Borax manufacture from Searles Lake brine 1-22 4. Anhydrous Borax process 1-23 5. Boric acid manufacture 1-25 6. Boric acid manufacture 1-26 7. Distribution of Boron uses 1-29 8. Boron concentration in plant tissues related to concentration in soil solution . . 1-52 9. Effect of Boron concentration on plant growth 1-76 v. ------- Volume I Preliminary Investigation of Effects on Environment of Boron and Its Compounds FOREWORD This is Volume I of a series of six reports on the environmental effects of boron, indium, nickel, selenium, tin, and vanadium and their conpounds. The information is based on literature reviews, direct con- tact with representatives of companies involved in the production or use of the materials, and consultation with knowledgeable individuals from industry, academic institutions and the Federal Government. ------- \R INC. 1-2 I. BORON INDUSTRY IN THE UNITED STATES A. Producers and sites Table I lists commercially significant chemical products and the companies involved. For this study significant is defined as production exceeding 1/2 metric ton or $1,000 value. Other materials may also be included in the discussion because of their unusual properties, such as toxicity, or their anticipated future significance. Table 1 Boron Products and Producers (1) Producer Chemical Aluminum diboridc Ammonium borate (Ammonium acid tetraborate) Ammonium fluoborate (Ammonium borofluoride) Antimony fluotorate Barium borotunqstate Boric acid (Boracic acid) Boric acid esters Boron Company, subordination Ventron Corp., Alfa Products Div. U.S. Borax & Chem. Corp. Allied Chem. Corp. Specialty Chems. Div. Kawecki Beryloc Indust., Inc. Kewanee Oil Co., Harshaw Chem. Co., Indust. Chems. Dept. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. City Chem. Corp. Allied Chem. Corp. Specialty Chems. Div. Kerr-McGee Corp. Kerr-McGee Chem. Corp., subsid. Stauffer Chem. Co. Indust. Chem. Div. U.S. Borax & Chem. Corp. U.S. Borax & Chem. Corp. Belmont Smelting & Refining Works, Inc. Fairmount Chem. Co., Inc. Kawecki Berylco Indust., Inc. Location Beverly, Mass. Wilmington, Del. Marcus Hook, Pa. Boyertown, Pa. Cleveland, Ohio Marcus Hook, Pa. Brooklyn, N.Y. Jersey City, N.J. Marcus Hook, Pa. Trona, Calif. San Francisco, Calif. Wilmington, Calif. Boron, Calif. Brooklyn, N.Y. Newark, N.J. Boyertown, Pa. ------- INC. 1-3 Table 1 (Con't) Itoron Products and Producers' Producer (1) Chemical Boron (Con't) Boron carbide Boron fluoride- cthylamine complex (Ethyl amine boron trifluoride) Boron fluoride orthophosphoric acid Boron nitride Boron oxide Boron phosphate Boron phosphide Company, subordination Kerr-McGee Corp. Kerr-McGee.Chem. Corp., subsid. Mine Safety Appliances Co. Gallery Chem. Co., div. U.S. Borax & Chem. Corp. U.S. Borax Research Corp., Ventron Corp. Chems. Div. Apache Chains., Inc. Fainrount Chem. Co., Inc. Kawecki Berylco Indust., Inc. Norton Co. Ventron Corp. Alfa Products Div. Kewanee Oil Co. Harahaw Chem. Co., div. Indust. Chems. Dept. Ozark-Mahoning Co. Kewanee Oil Co. Harshaw Chem. Co., div. Indust. Chems. Dept. The Carborundum Co. Refractories and Electronics Div. Fairmount Chem. Co., Inc. Kawecki Berylco'Indust., Inc. Ventron Corp. Alfa. Products Div. Allied Chem. Corp. Specialty Chems. Div. Eagle-Picher Indust., Inc. Electronics Div. Stauffer Chem. Co. Indust. Chem. Div. Ventron Corp. Alfa Products Div. Ventron Corp. Alfa Products Div. Location Henderson, Nev. Gallery, Pa. subsid. Anaheim, Calif. Wood Ridge, N.J. Rockford, 111. Newark, N.J. Boyertown, Pa. Worcester, Mass. Beverly, Mass. Cleveland, Ohio Tulsa, Okla. Cleveland, Ohio Latrobe, Pa. Newark, N.J. Boyertown, Pa. Beverly, Mass. Marcus Hook, Pa. Miami, Okla. Quapaw, Okla. San Francisco, Calif. Beverly, Mass. Beverly, Mass. ------- fAK INC. Chemical Boron tribromide Boron trichloride Boron trifluoride Table 1 (Can't) Boron Products and Producers Producer (1) Boron trifluoride ethyl ether conplex Company, subordination Eagle-Picher Indust., Inc. Electronics Div. Kerr-McGee Corp. Kerr-McGee Chem. Corp., subsid. Allied Chem. Corp. Specialty Chems. Div. Kerr-McGee Corp. Kerr-McGee Chem. Corp., subsid. Allied Chem. Corp. Specialty Chems. Div. Kewanee Oil Co. Harshaw Chem. Co., div. Indust. Chems. Dept. Allied Chem. Corp. Specialty Chems. Div. 1-4 Location Miami, Okla. Quapaw, Okla. Henderson, Nev. Marcus Hook, Pa. Henderson, Nev. Marcus Hook, Pa. Cleveland, Ohio Cleveland, Ohio Marcus Hook, Pa. Boron trifluoride- phenol conplex Allied Chem. Corp. Specialty Chems. Div. Marcus Hook, Pa. Boron triiodide Ventron Corp. Alfa Products Div. Beverly, Mass. Boroxines (unspecified) Calcium borate Calcium boride (calcium hexaboride) Chromium boride (mono) Chromium fluoborato Cobalt borate (Cobaltous borate) Cobalt fluoborate (Cobaltous fluoborate) Mine Safety Appliances Co. Gallery Chem. Co., div. Ttenneco Inc. Tenneco Oil Co., Div. U.S. Borax & Chem. Corp. U.S. Borax Research Corp., subbid. Molybdenum Corp. of America Chains, and Pare Earth Div. Ventron Corp. Alfa Products Div. U.S. Borax & Chem. Corp. U.S. Borax Research Corp. Ventron Corp., Alfa Products Div. Allied Chem. Corp. Specialty Chems. Div. The Shepherd Chem. Co. Harstan Chem. Corp. Ventron Chem. Corp. Alfa Products Div. Gallery, Pa. Death Valley Junction, Calif. Anaheim, Calif. Washington, Pa. Beverly, Mass. * Anaheim, Calif. Beverly, Mass. Marcus Hook, Pa. Cincinnati, Ohio Brooklyn, N.Y. Beverly, Mass. ------- 'AH INC. Table 1 (Can't) 1-5 ,(1) Boron Products and Producers Producer Chemical Copper borate (Cupric borate) Copper fluoborate (Cupric fluoborate) Indium fluoborate Iron borate (Ferric borate) Iron fluoborate (Ferrous fluoborate) Lead borate Lead fluoborate (Plumbous fluoborate) Lithium borohydride Lithium fluoroborate Magnesium borate Magnesium fluoborate Company, subordination City Chem. Corp. The Shepherd Chem. Co. Allied Chem. Corp. Specialty Chems. Div. liars tan Chem. Corp. Kewanee Oil Co. Harshaw Chem. Co. Indust. Chems. Dept. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. The Indium Corp, of America City Chem. Corp. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. Humphrey Chem. Corp. The Shepherd Chem. Co. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. Kewanee Chem. Co. Harshaw Chem. Co. Indust. Chems. Dept. Mine Safety Appliances Co. Gallery Chem. Co. Ventron Corp. Alfa Products Div. Chems. Div. Foote Mineral Co. Ozark-Mahoning Co. Ventron Corp. Alfa Products Div. The Shepherd Chem. Co. Allied Chem. Corp. Specialty Chems. Div. Kewanee Oil Co. Harshaw Chem. Co. Indust. Chems. Dept. Location Jersey City, N.J. Cincinnati, Ohio Marcus Hook, Pa. Brooklyn, N.Y. Cleveland, Ohio Cleveland, Ohio Marcus Hook, Pa. Brooklyn, N.Y. Utica, N.Y. Jersey City, N.J. Marcus Hook, Pa. Brooklyn, N.Y. Edgewcod Arsenal, Md. Cincinnati, Ohio Marcus Hook, Pa. Brooklyn, N.Y. Cleveland, Ohio Gallery, Pa. Beverly, Mass. Exton, Pa. Tulsa, Okla. Beverly, Mass. Cincinnati, Ohio Marcus Hook, Pa. Cleveland, Ohio ------- :R/AR IMC, Chemical Manganese borate (Manqanous borate) Manganese boride Manganese fluoborate (Manganous fluoborate) Molybdenum boride, mono , di- Nickel fluoborate (Nickelous fluoborate) Table 1 (Can't) l'3oron Products and Producers (1) 1-6 Niobium boride (Niobium dibbride) Phosphine boranes Potassium borohydride Potassium fluoborate Producer Conpany, subordination Chemetron Corp., Chains. Group, Inorganic Chems. Div. Gen. Metallic Oxides Co. The Shepherd Chem. Co. Molybdenum Corp. of America Chems. and Rare Earth Div. City Chem. Corp. U.S. Borax & Chem. Corp. U.S. Borax Research Corp. Allied Chem. Corp. Specialty Chems. Div. American Can Co. M&T Chems. Inc. Harstan Chem. Corp. Kewanee Oil Co. Harshaw Chem. Co. Indust. Chems. Dept. Ozark-Mahoning Go. Ventron Corp., Alfa Products Div. Kawecki Beryloo Indust., Inc. U.S. Borax & Chem. Corp. U.S0 Borax Research Corp. Ventron Corp. Alfa Products Div. Mine Safety Appliances Co. Gallery Chem. Co. Mine Safety Appliances Co. Gallery Chem.' Co., div. Ventron Corp. Chems. Div. Allied Chem. Corp. Specialty Chems. Div. Borden Inc. Borden Chems. Div. Smith-Douglass Kawecki Berylco Indust., Kewanee Oil Co. Harshaw Chem. Co. div. Indust. Chems. Dept. Inc. Location Cleveland, Ohio Jersey City, N.J. Cincinnati, Ohio Washington, Pa. Jersey City, N.J. Anaheim, Calif. Marcus Hook, Pa. East Chicago, Ind. Brooklyn, N.Y. Cleveland, Ohio Tulsa, Okla. Beverly, Mass. Boyertcwn, Pa. i Anaheim, Calif. Beverly, Mass. Gallery, Pa. Gallery, Pa. Beverly, Mass. Marcus Hook, Pa. Plant City, Fla. Boyertown, Pa. Cleveland, Ohio ------- 'MjAR INC. Table 1 (can't) Boron Products and Producers (1) 1-7 Producer Chemical Potassium fluoborats (con't) Rubidium borohydride Silicon hexaboride (Hexaboron silicide) Silicon tetraboride Silver fluorborate Sodium borodeuteridc Sodium borohydride Sodium fluoborate (Sodium borofluorido) Sodium Octaborate Sodium Pentoboratc Sodium perborate, monohydrato Company, subordination Ozark-Mahoning Co. Ventron Corp. Alfa Products Div. Ventrcn Corp. Alfa Products Div. Ventron Corp. Alfa Products Div. Mallinckrodt Chem. Vforks Indust. Chems. Div. Ventron Corp. Alfa Products Div. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. Ozark-Mahoning Co. Ventron Corp. Alfa Chems. Div. Ventron Corp. Alfa Products Div., Chains. Div. Mine Safety Appliances, Co. Gallery Chem. Co., div. Ventron Corp. Alfa Products Div. Chems. Div. Allied Chem. Corp. Specialty Chems. Div. Kawecki Berylco Indust., Inc. Kewanee Oil Co. Harshaw Chem. Co., div. Indust. Chems. Dept. Ozark-Mahoning Co. Ventron Corp. Alfa Products Div. U.S. Borax & Chem. Corp. Kerr-McGee Corp. Kerr-McGee Chem. Corp., subsid. Corp. Inorganic Chems. Div. Location Tulsa, Okla. Beverly, Mass. Beverly, Mass. Beverly, Mass. St. Louis, Mo. Beverly, Mass. Marcus Hook, Pa. Brooklyn, N.Y. Tulsa, Okla. Beverly, Mass. Beverly, Mass. Beverly, Mass. Gallery, Pa. Beverly, Mass. Beverly, Mass. Marcus Hook, Pa. Boyertown, Pa. Cleveland, Ohio Tulsa, Okla. Beverly, Mass. Wilmington, Calif. Trona, Calif. Buffalo, N.Y. ------- 'A R INC. Table 1 (Can't) F3oron Products and Producers (1) 1-8 Producer Chemical Sodium perborate tetrahydrate (Sodium metaborate peroxyhydrate) Sodium tetraborate (Borax) (Produced as Anhydrous Borax, Borax decahydrate, and Borax pentahydrate) Sodium tetraphenylboror (Sodium tetraphenylborate) Tantalum diboride Tin fluoborate (Stannous fluoborate) Titanium diboride (Titanium boride) Tunqsten monoboride Vanadium diboride Zinc borate Company, subordination E. I. duPont de Nemours & Co., Inc. Indust. Chems. Dept. Filo Color & Chem. Corp. EMC Corp. Inorganic Chems. Div. Kerr-McGee Corp. Kerr-MoGee Chem. Corp., subsid. Occidental Petroleum Corp. Searles Lake Chem. Co., subsid.* Stauffer Chem. Co. Indust. Chem. Div. U.S. Borax & Chem. Corp. Allied Chem. Corp. Specialty Chems. Div. Richardson-Msrrell, Inc. J.T. Baker Chem. Co., subsid. Kawecki Berylco Indust., Inc. Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. Kewanee Chem. Corp. Harshaw Chem. Co. Indust. Chems. Dept. Kawecki Berylco Indust., Inc. U.S. Borax & Chem. Corp. U.S. Borax Research Corp. Ventron Corp. Alfa Products Div. U.S. Borax & Chem. Corp. .U.S. Borax Research Corp. U.S. Borax & Chem. Corp. U.S. Borax Research Corp. Ventron Corp., Alfa Products Div. Hunphrey Chem. Corp. Maryland Zinc & Research Co. U.S. Borax & Chem. Corp. Ventron Corp. Alfa Products Div. Location Memphis, Term. Newark, N.J. Buffalo, N.Y. Trona, Calif. Searles Lake, Calif. West End, Calif. Boron, Calif. Marcus Hook, Pa. Phillipsburg, N.J. Boyertown, Pa. Marcus Hook, Pa. Brooklyn, N.Y. Cleveland, Ohio Boyertown, Pa. Anaheim, Calif. Beverly, Mass. Anaheim, Calif. Anaheim, Calif. Beverly, Mass. Edgewood Arsenal, Md. Cockeysville, Md. Wilmington, Calif. Beverly, Mass. ------- KK/AR INC, 1-9 Chemical Zinc fluoborate Zirconium diborido (Zirconium boride) Table 1 (Con't) «. Boron Products and Producers Producer Company, subordination Allied Chem. Corp. Specialty Chems. Div. Harstan Chem. Corp. Kewanee Oil Co. Harshaw Chem. Co. Indust. Chems. Dept. Mineral Research and Dev. Corp. Ventron Corp. Alfa Products Div. Kawecki Berylco Indust. Inc. U.S. Borax & Chem. Corp. U.S. Borax Research Corp. Location Marcus Hook, Pa. Brooklyn, N.Y. Cleveland, Ohio Concord, N.C. Beverly, Mass. Boyertown, Pa. Anaheim, Calif. Decaborane Diborane Octadecaborane Pcntaboranc BORANES (Inorganic) Mine Safety Appliances Co. Gallery Chem. Co., div. Mine Safety Appliances Co. Gallery Chem. Co., div. G. D. Searle & Co. Will Ross, Inc., subsid. Matheson Gas Products, div. Ventron Corp. Alfa Products Div. Mine Safety Appliances Co. Gallery Chem. Co., div. Gallery, Pa. Gallery, Pa. Cucamonga, Calif. East Rutherford, N.J. Gloucester, Mass. Joliet, 111. La Porte, Tex. Morrow, Ga. Newark, Calif. Beverly, Mass. Gallery, Pa. ORGANIC BORON COMPOUNDS Dimethylamine borone Dioxaborii lanes Mine Safety Appliances Co. Gallery Chem. Co., div. U.S. Borax & Chem. Corp. Gallery, Pa. Boron, Calif. ------- I W/AR INC. 1-10 Table 1 (Can't) (1) iBoron Products and Producers Producer Chemical Hexylene borate Morpholine borane Company, subordination Kipers Labs. Ventron Corp. Alfa Products Div. Chems. Div. Sodium tetraphenylkoron Allied Chem. Corp. (Sodium tetraphenyllxirate) Specialty Chems. Div. Richardson-Merrell, Inc. J.T. Baker Chem. Co., subsid. tert-Butylamine borane Trialkyl boranes Tributyl borate (Butyl borate) Tri-m, p-cresyl borate Tricyclohexyl borate Triethanolamine borate TriethyIborane (Triethylborine) Triethyl borate (Tricthoxy borane) Triethyloxonium tetra- fluoroborate Tri (hexylcne glycol) biborate Tri isobutyIborane Triisopropyl borate Mine Safety Appliances Co. Gallery Chem. Co., div. Ventron Corp. Alfa Products Div. Stauffer Chem. Co. Specialty Chem. Div. Anderson Dev. Co. U.S. Borax & Chem. Corp. U.S. Borax Research Corp., subsid. Anderson Dev. Co. U.S. Borax & Chem. Corp. U.S. Borax Research Corp., subsid. Mine Safety Appliances Co. Gallery Chem. Co., div. Texas AlkyIs, Inc. Ventron Corp. Alfa Products Div. Anderson Dev. Co. U.S. Borax & Chem. Corp. y U.S. Borax Research Corp., subsid. Ventron Corp. Alfa Products Div. U.S. Borax & Chem. Corp. U.S. Borax Research Corp., subsid. Texas AlkyIs, Inc. Anderson Dev. Co. Stauffer Chem..Co. Specialty Chem. Div. Ventron Corp. Alfa Products Div. Location Santa Ana, Calif. Beverly, Mass. Beverly, Mass. Marcus Hook, Pa. Phillipsburg, N.J. Gallery, Pa. Beverly, Mass. Vfeston, Mich. Adrian, Mich. Anaheim, Calif. Adrian, Mich. Anaheim, Calif. Gallery, Pa. Deer Park, Tex. Beverly, Mass. Adrian, Mich. Anaheim, Calif. Beverly, Mass. Anaheim, Calif. Deer Park, Tex. Adrian, Mich. Weston, Mich. Beverly, Mass. ------- / KRfAR INC, 1-11 Table 1 (Cant) »» Boron Products and Producers Producer Chemical Trinethoxyboroxine (Methyl metaborate) Tri-2-methoxyethyl borate Trimethyl borate (Methyl borate) (Trimethoxyborine) Trimethyl borate- methanol azeotrope Company/ subordination Mine Safety Appliances Co. Gallery Chem. Co., div. Stauffer Chem. Co. Specialty Chem. Div. Anderson Dev. Co. Anderson Dev. Co. Mine Safety Appliances Co. Gallery Chem. Co., div. Stauffer Chem. Co. Specialty Chem. Div. Ventron Corp. Chems. Div. Ventron Corp. Alfa Products Div. Location Gallery, Pa. Weston, Mich. Adrian, Mich. Adrian, Mich. Gallery, Pa. Wsston, Mich. Danvers, Mass. Beverly, Mass. * Scheduled late 1974 ------- 1-12 B. Costs and Physical Properties of Important Boron Compounds The prices of selected boron minerals and chemicals are given in Table 2. The materials listed are the most commercially significant of the boron family. Another common factor is that their most important applications are based on their boron oxide (B^O.,) content. In many instances these materials are interchangeable. In 1970 anhydrous borax was the least expensive in B-CL content, but under 1974 prices borax pentahydrate is cheapest. Physical properties of the most important boron compounds are presented in Table 3. A Many metals form borides of various compositions. Most are specialty materials only, but a few are used in the aerospace industry. In general, environmental effects are minimal. Many of the netal borides oxidize in air considerably below the listed melting points. This limits the significance of the high melting points (e.g., vanadium and tungsten borides oxidize in air at less than 1200C versus listed melting points of 2000 - 3000C. As a rule the melting point of a parti- cular boride composition increases with the atomic weight in a Group but de- creases with increasing atomic weight in each period. Hafnium and tantalum borides therefore have the highest malting points - 3250 ± 100C and 3400 ± 50C. ------- Table 2 (2) Prices of Boron Minerals and Chemicals Borax decahydrate Borax pentahydrate Anhydrous borax Boric acid Boric oxide bags buLk bags .bulk bags bulk bags bulk bags bags bulk B_0, Content , % . 36.3 36.3 47.56 47.56 68.5 68.5 56.24 56.24 99.9 95-96 95-96 Price in Carlots, f.o.b. Plant 1970 Prices (?) per metric ton per unit B?C 53 45 68 60 93 84 113 104 360 159 149 1.46 1.24 1.43 1.26 1, 1, 2, 1. 3. 1, 36 26 01 83 60 67 1974 Prices (5) per metric ton per unit 73 60 86 73 159 145 169 148 573 2.01 1.65 -1.81 1.53 2.33 2.12 3.01 2.63 57.2 1.56 I CO ------- Table 3 Physical Properties Chemical Bcron Sodium tetraborate Decahydrate (Borax) Sodium tetraborate Pentahydrate Sodium tetraborate Anhydrous Colemanite* Boric Acid Boric oxide Boron trifluoride Boron trichJ.oride Sodium fluoborate Potassium fluoborate Anmonium fluoborate Specific Gravity 2 . ? 4 crys 2.37 amor 1.73 1.815 2.67 2.42- 2.43 1.435 15°C 2.46 crys 1.812 glass 2.99 g/1 (gas) 1 i** 1.349/1 4 2.4720 2.49820 Siting Point °C 23CO 75 120 -H20 741 — 169 to HBO2 460 -126.7 -107.3 si d 384 d350 Boiling Point °C 2550 sub 320 -10H20 — 1575 d — " — 300 -1 1/2 H20 1860 -99.9 12.5 d d Solubility Water g/lOOcc °C Insol. 2.01 g 0 170 g 100 22.65 g 65 52.3 8 100 1.05 8 0 8.79 8 40 ^""^ 6.3530 27.6100 inn 15. 7100 106 cold d hot d hot 10826 i nn 2101UU 0.44-mn (• 0-7-LUU D .^ / Coiments 0.001% earth's crust combined form only Natural mineral %D C\ 1C. "5 B_U^ — jo . J Natural mineral S B203- 47.5 % B.O - 68.5 2 3 Natural mineral HBO Ortho form boron trioxide fumes in moist air pungent odor fumes in moist air emits hydrogen chloride Natural avogadrite 1.871 15 subl 25 97 100 **Sp.Gr. at 11°C referenced to water at 4°C ------- Chemical Diborane Boron (betra) carbide Boron nitride Specific Gravitv J-.1Q. 0.447 2.52 2.25 -11 -165.5 2350 subl ca 3000 Table 3 (Con't) Physical Properties Boiling Point °C -92.5 73500 Solubility Water g/lOQcc °C si. s, d cold water Conrnents Boron hydride i cold, si d hot i Ol ------- M/AR INC, 1-16 II. PRODUCTION A. Natural Sources of Borates The nap in Figure 1 shows the location of the significant borate deposits in the United States. They produce virtually all of the raw materials for the boron industry, in the U.S. Approximately 20% of the present production stems from the utilization of Searles Lake brines. Significant colemanite (Table 3) rtiining is also performed by Tenneoo. Total borate production by company and location is presented in Table 4.' B. Manufacturing Processes 1. Elemental Boron Although widespread in nature boron occurs naturally only in combined form. Elemental boron is not one of the more inportant commercial forms of boron. Three general techniques are used to prepare boron from its compounds: (1) Chemical reduction with active elements, (2) Non-aqueous electro- lytic reduction, and (3) Thermal decomposition. Beduction of boron compounds to elemental boron has been carried out with magnesium, hydrogen, and many other elements. Among the boron compounds used are borates, boron oxides, boron halidas, fluoborates, and borohydrides. The most common method for producing large amounts of elemental boron is the exothermic reduction (thermit reaction) of boric oxide with magnesium. The product of this reaction, a finely-divided powder known as "Moissum's boron" is amorphous as is boron produced from any of the chemical reduction methods except for high temperatuie reduction by hydrogen. The latter method, especially when involving hot filament reaction of hydrogen with boron tribromide, has become a conventional means for obtaining boron with purities of 99% and higher. Electrolytic preparation of boron usually involves the passage of a current through fused melts of boric oxide in potassium halides or oxides. Electrolysis of potassium fluorborate-potassium chloride or potassium chloride- sodium chloride melts is performed with a boron carbide anode. The purity of the product obtained by these methods has been 87-99.8%. Direct electrolysis ------- 1-17 OREGON >CHELCO(PRICEITE) BORATE DEPOSITS IN OREGON DISCOVERED AND WORKED DURING EARLY PERIOD LAKE NEVADA TEELS MARSH RHODES MARSH COLUMBUS MARSH FISH LAKE VALLEY SAN FRANCISCO C ALIFORNIA (BORAX CRYSTALS MUD)FIRST DISCOVERY OF BORAX 1856 PRODUCTION 1864-1874 SEARLES L , (BRINE) ' CURRENT SOURCE SAM BERNARD/NO 1COUNTY DEPOSITS NOW ABANDONED BUT WERE IMPORTANT SOURCES DURING EARLY STAGES BARTLETT (BRINE) SMALL PRODUCTION 1929-1953 TRONA FRAZIER MOUNTAIN DISTRICT (COLEMANITE) PRODUCTION 1899-1907, 1911 -1913 KRAMER DISTRICT*BORON)-" (BORAX AND KERNITE ORE) MAIN SOURCE SINCE 1927 CAVE SPRING (VEINLETS OF SEARLESITE) ACE CREEK DISTRICT (LAKE DEPOSITS AND COLEMANITE) MAIN SOURCE OF PRODUCTION 1915-1926 ILA C. MINE (COLEMANITE) LARGEST PRODUCER IN 1912 ESTLEY-SHOSHONE MINE(ULEXITE AND COLEMANITE) PRODUCTION 1915-1926 LANG (COLEMANITE) PRODUCTION 1908-1923 WHITE BASIN(COLEMANITE) PRODUCTION 1924-1962 CALLVILLE WASH (COLEMANITE) PRODUCTION 1921-1927 IR CORNERS (COLEMANITE) CALICO MOUNTAIN DISTRICT {COLEMANITE) PRODUCTION 1887-1907 Figure I Location of Borate deposits in ------- 1-18 Table 4 74) Production of Borates in the United States as of 1972 Company U.S. Borax & Chemical Corp. Quantity > 500,000 metric tons as B^O, combined capacity 23 annual ~ Location Boron, California Products crude borax refined borax anhydrous borax boric acid boric oxide Kerr-McGee Chemical Corp. Stauffer Chcm. Corp. Tenneco Oil Company Searles Lake Chem. Co. Subsid. of Occidental Pet. Corp. approx. 100,000 metric tons B-O, capacity : 25-30,000 metric tons capacity B2°3 Searles Lake, Trona, California Searles Lake, Trona, California Design-150,000 metric tons raw colemanite Design- 70,000 metric tons calcined colemanite Production: metric tons calcined colemanite 6,300 metric tons 24,000 metric tons* Furnace Creek, California Searles Lake, Calif. boron compounds boron compounds colemanite ore calcined colemanite borax 'Scheduled late 1974. Miy be indefinitely postponed. ------- VKR/A \f fAR IMC, 1-19 of alkali or alkaline earth berates yields a product of J.ower purity. Electrolysis has not been an important commercial method for the production of elemental boron. Boron compounds that can be decomposed to high purity forms of boron are limited to the halides and hydrides. Boron tribromide, boron triiodide, and boron hydrides (from diborane to decaborane) have been de- composed on a wide variety of substrates ranging from glass to tungsten at temperatures from 800 to 1500C. 2. Borax The entire U.S. production of borax is carried out in the desert areas of California by two processes. The borax ore is either mined and extracted or, as in Searles Lake, taken from the brines by the Trona process. a. The Mining Process The mining operation starts at the larger, deep open pit mines. Explosives and electric shovels break up the ore. An automatic ore conveyor belt, starting in the pit at the 225 foot level, then carries the ore to the surface and nearby concentrating and refining plants. This natural material is principally borax (sodium tetraborate decahydrate) and kernite (sodium tetraborate tetrahydrate). Both of these minerals must be processed to remove impurities and produce the primary commercial compounds: (1) sodium tetraborate decahydrate; (2) sodium tetraborate pentahydrate; and (3) anhydrous sodium tetraborate. The refining process begins by crushing and dissolving the ore to remove the impurities. The ore is next thickened, recrystalized and dried. Some of the material is crystallized and produced as decahydrate,, some as pentahydrate. The remainder is fused in a furnace to the anhydrous state. (Figure 2) Waste- water treatment consists of percolation-proof evaporation ponds„ Tl >ei~ i •* no plant effluent and the intake water and wastewater sent to the evaporation ponds are thoroughly monitored. ' ------- BORAX ORE I-10 CRUSHER WATER- -m , RECYCLE < MOTHER / LIQUOR WASH WATER DIS80LVER THICKENER CRYSTALLIZER CENTRIFUGE •WASTE WATER 'CONTACT COOLING .WATER DRYING AND SCREENING ;TS »VENT Borax production from ore ------- KR/Alt INC. 1-21 b. Trona Process Brine from Searles Lake is processed to produce borax and other chemicals at two highly integrated facilities located at Trona, Cali- fornia. The recovery processes and raw materials are unique to this location. The area is desert land immediately adjacent to Searles Lake, a large residual evaporate salt body filled with saline brines. The brines ore pumped into the processing facilities. The procedures used to yield crude borax are shown in Figure 3. The residual brines, salts, end liquors, and added process waters are returned to the salt body to maintain the saline brine volume. The recycle liquors are actually the medium for producing the raw material for the processes so there is not a "discharge". The crude borax combined with borax solids from the separate carbonation-refrigeration process, is purified by recrystallization, dried, and packaged. 3. Anhydrous Borax Anhydrous borax is either made from coarse granular decahydrate or from wet decahydrate from the centrifuges. Figure 4 shows a diagram of one process used for the manufacture of anhydrous borax. Two features of this process deserve comment. First, the dust from the calciners is recovered and reprocessed and second, the product can be obtained in either the crystalline or annrphous form. Commercial anhydrous borax is mainly the latter type. 4. Boric Acid lioric acid is made by reacting borax and sulfuric acid. Since the U.S. sources of: borax production are in the California desert areas, that is where the boric acid production is located. Approximately 70 percent of U.S. production of boric ncid is based on borax from mined ore, the remainder cones from borax extracted from lake brines. To produce boric acid from the mined ore borax tetraborate and sulfuric acid are reacted and the resulting slurry is vacuum filtered,, The solid boric acid is dissolved in water, filtered, reprecipitated in air coolerss separated by oentrifugation, washed, dried, and packaged. The original liquor is recycled with excess liquor wasted because of water imbalance. Diagrams of ------- 1-22 RAW BRINE HEAT EXCHANGER TRIPLE EFFECT EVAPORATORS CRYSTALLIZER ( ! SALT SEPARATOR | SOLIDS TO OTHER PROCESSES AMMONIA COOLING WATER• STEAM • VACUUM COOLER CONE SETTLER AND FILTER BORAX LIQUOR DORR THICKENER FILTER DISSOLVER FILTER DRYER KCI TO OTHER PLANT USE CRYSTAi ' ' | > DEPLETED LIQUOR KCI PRODUCT x RETURN TO /BRINE SOURCE DEPLETED LIQUOR VACUUM CRYSTALLIZER CENTRIFUGE DRYER Figure 3 Borax manufacture from Seariss Lake CRUDE BORAX ------- BORAX CALCINERS OUST WATER—C=^ FUSION FUKNACE WATER- COOLED ROLLS CRUSHING AM) SCREENS AMORPHOUS PRODUCT MOLDS J3WSTALUKE 4 K> CO ------- KR/AR INC. i-24 processes used at two installations are shown in Figures 5 and 6. ' 5. Boric oxide (B203, boron trioxide) Boric oxide may be prepared by the fusion of boric acid. If this method is used, tlie boric oxide generally contains up to 0.5% water, depending on the temperature and other fusion parameters. If the temperature is at least 1300C, the product is nearly anhydrous. If ground boric acid is heated slowly to 260-27OC in a 1 to 2 mm mercury vacuum and maintained at this temperature for six hours, an active, practically anhydrous form-of boric oxide is produced. This boric oxide dissolves very rapidly in water with a hissing sound. 6. Boron tri fluoride (BFj Two processes are in general commercial use for the production of boron trifluoride. In one, borax is added slowly to hydrofluoric acid to produce water and Na20(BF3)4. The latter, "fluoborax", is treated with cold fuming sulfuric acid in a generator. The reaction mixture is slowly heated. The generation of boron trifluoride is controlled by the temperature. This method can also be used by mixing boric acid with ammonium bifluoride, in which case the boron trifluoride complex from which boron trifluoride is gener- ated is (NHJJXBF-) ... The other commercial process is to react fluorosulfonic 4 £ j (8) acid with boric acid. 7. Boron trichloride Boron trichloride is commercially produced by several different methods. One method is by chlorinating a mixture of finely divided carbon and boric oxide at 870 to 980 C. A second method is heating boric oxide with sodium, potassium, or lithium chloride at 800 to 1000C. Between 500 and 1500C sodium borofluoride and magnesium chloride can also be combined to produce /g\ boron trichloride. 8. Diborane and higher boranes (pentaborane, etc.) Diborane is prepared by the reaction of boron trichloride with lithium aluminum hydride in anhydrous diethyl ether or with lithium hydride, sodium borohydride, or sodium trimethoxyborohydride in diethyl ether solution. (8) 'itie higher boranes ore produced by the controlled pyrolysis of diborane. ------- 1-25 SULFURIC ACID BORAX REACTOR RECYCLE LIQUOR WASTE LIOUOR FILTER fir CAKE REPULPER AND REDISSOLVER FILTER AIR COOLER CENTRIFUGE TECHNICAL GRADE BORIC ACID PRODUCT Boric acid -.WASTE LIOUOR .WASH DOWN WASTE ------- SULFURIC ACH> FINE BORAX REACTION TANK TANK S'ENT TO OTHER \«»TER VAPOR t VACUUM CRYS1ALLJZER CENTRIFUGE SFENT LIQUOR WATER - STEAM- DRTER CRU3E AOD PROiXICT DSSSGLVER RERNSD Figure 6 Boric acid manufacture ------- I KR/AR INC. 1-27 9. Refractory boron compounds (metal borides, boron carbide, and boron nitride) The most extensively used methods for producing refractory boron compounds are the following: (a) The direct reduction of metallic boron with the metal. (b) The use of reducing agents such as aluminum, silicon, magnesium, carbon, or boron and boric oxide-metal oxide mixtures. (c) The electrolysis of fused-salt mixtures containing metal oxides and boron oxides. (d) Deposition from the vapor phase. The first, and the most common method for making boron carbide, is .reacting boron oxide and carbon at 1400-2300C. The use of finely divided carbon such as carbon black speeds the reaction. The cubic crystal form of boron nitride is made by the synthetic diamond production techniques of high temperatures and high pressures. At this point, its commercial significance is fairly limited; however, it is available. ------- 1-28 \R INC. IIT. USES OF BORON COMPOUNDS A. The majority of boron used in the United States is in the form of borax (Na?B 0•10H-0). Figure 7 presents an overall picture of the uses of boron and its compounds. A detailed summary of current boron usage is presented in Table 5. ------- 1-29 ENAMELS, FRITS GLAZES! 26% MINOR USES 15% SOAPS CLEANSERS HERBICIDES \ FERTILIZER 40-45% GLASS MANUFACTURE Figure 7 Distribution of Boron uses ------- Borcn Conpound Elemental boron Use Steel Non ferrous metallurgy Table of Uses Table 5. (4,5,7,8,9) Purpose Deoxidizing and alloying element in the form of ferroboron alloy Increases hardness of steel Alloying agent Gormen ts Dissolves rapidly in molten steel Amount used under 0.003% Boron concentration varies from 20% to less than 0.1% Borax Boric Acid and Anhydrous Borax Manufacture of borosilicate and similar glasses Optical glass Gives desired properties including the index of refraction BO- essential to impart the low coefficient of expansion required For glass, to maintain the proper acid-alkali ratio borax is supple- mented with substantial quantities of boric acid Borax Glass containers Novelty ware Structural glass Flat glasses Cleaning room of enamel plants Aids in the melting, finishing, and forming operation Enhances color, durability, scratch resistance and strength of finished product Used as an alkali Borax only used in small amounts Steel and steel plating Leather industry Detergent, hand cleaner, face cream, cosmetics Final dip serves as a rust preventative and aid in bonding the first coat to the iron body. Mild alkali and preservative Mild alkali and buffer Used alone or in conjunction with other materials. Used blended with soap Bacterial characteristics and easy solubility in water ------- Table of Uses Boron Ccrpound Borax and Anhydrous Borax Borax and Boric Acid Use Manufacture of vitreous enamel frits Pottery glazes Colored glass for decoration and marking purposes Other Table 5 (Con't) Purpose Same benefits as in alass manufacture Comments Improves the resistance to fire of textiles, lurrber and other conbus.tible materials Treatment for epilepsy, soothing oint- ments, rectal and colonic irrigations and vaginal douches Wood is impregnated under pressure with preservatives such as pentachloro- phenol and borate solution for fire proofing in a single pass through a pressure chamber Mildly antiseptic and antifungal, but not sufficiently so for most purposes Boric Acid Manufacture of metal berates, hydrids, master alloys, and as a catalyst in many organic reactions Use as a catalyst in air oxidation of hydrocarbons accounted for more than 3% of overall boron consumption Boron Trifluoride Petroleum Refining Organic synthesis Catalyst in isomerization, alkylation, polymerization, esterification, con- densation, cyclization, hydration, de- hydration, sulfonation, desulfurization, nitration, halogenation, oxidation and acylation Catalyst in the Friedel-Crafts type of reaction, the synthesis of saturated hydrocarbons, olefins, alcohols, thiols, ketones and ethers, in cracking hydro- carbons i OJ ------- Table of Uses Table 5. (Can't) Boron Compound Boron Trlfuoride Use Preparation of boranes Magnesium alloy castings Puroose Conments Diborane is the only commercial borane of importance being pro- duced at oresent Protects molten magnesium and alloys from oxidation during casting and a flux for soldering magnesium Boron Trichloride Refining aluminum, magnesium, zinc, and copper alloys Soldering flux for alloys of aluminum, iron, zinc, tung- sten and monel. Aluminum castings Removes nitrides, carbides and oxides from the molten metal Removes occluded gases, such as gen, nitrogen, carbon monoxide, nitrides, carbides and oxides hydro- Manufacture of electrical resistors Extinguishing mag- nesium fires in heating furnaces High energy fuels and rocket pro- pellants Catalyst A source of boron for raising the BTU value Suggested use in the polymerization of styrene Grain growth of aluminum also retarded making it more uniform Improves the tensile strength and will permit the remelting of the aluminum without substantially changing the grain structure Uniform and lasting adhesive carbon film can be put over a ceramic base by a process that has been developed in- volving the addition of boron tri- chloride to benzene at high temperatures Forms a magnesium chloride film that smothers the fire by preventing air from reaching the metal GJ NJ Reportedly yields polymers with 3X the molecular weight of those produced with other catalysts ------- Table of uses Table 5. (Can't) Boron Compound Diborane Use Plastics Pro- duction Rubber Vulcanization Other Purpose Catalyst for ethylene, styrene, acrylic and vinyl polymerization Reducing agent Flame-speed acceleration Inte mediate for high boron hydrides Doping gas Comments Boron Carbide Grinding highly abrasive material Refractory usage Jet aircraft parts, rocket chambers and gas turbines Self-bonding ability allows it to be molded in graphite and pressed at temperatures up to 2400C into high-density, nonporous shapes Negative thermal coefficient of electrical resistance Considered a semiconductor Boron nitride High-teniperature abrasive Properties similar to boron carbide and can be used for the sane purposes When present in the cubic crystal form more stable than diamond in air at high temperatures CO CO ------- / KR/AR INC, i_34 B. Futupe and Potential Uses The annual U.S. producticn of boron minerals and chemicals from raw material supplies has increased steadily at a rate of six. to seven per cent per year since the early 1960's. Roughly half of the boron produced is retained for domestic consumption. No new or expanded uses of boron are anticipated to effect the industry in the near future. Elemental boron has found only limited use as a thermistor material, on intrinsic semiconductor, a photoconductor and a heat-resistant infrared window material. Tte main obstacle to these uses has been the lack of suitable production and analytical techniques. Progress has been made, however, in elemental boron purification technique. This should enable greater use of this material in electronic and optical devices. The demand for glass fibers should increase through the 1970's. In part this will be due to the demand for auto tires, but to a considerably greater extent increased demand can be attributed to the popularity of rein- forced plastics. Colemanite is highly desirable in this application as a non- sodium source of B,0^. One estimate is that the demand for glass fibers in reinforced plastics would increase from 115.4 million kg in 1969 to 412.8 million C2\ kg in 1975 and 757.5 million kg by 1980.v ' A potentially significant demand for borates, possibly colemanite, as a substitute for fluorspar in the basic oxygen-furnace steel manufacturing process has been under consideration for over five years. At the present time this does not appear promising. The substitution of oolemanite for fluorspar (4) did not go beyond the pilot plan stage in ,1972. Many companies have shown a great deal of interest in boron industry. Many organic and inorganic boron monomers and polymers have been synthesized and studied. So far no new large-volume boron-containing chemical has emerged (2) and none appears likely. ------- KR/AR INC. 1-35 IV. CURRENT PRACTICES Borax, colemanite, sodium tetraborate, the various forms of borax, oolemanite and anhydrous borax (sodium tetraborate) are sold in bags, barrels/ and bulk. Boron trifluoride is included in the "List of Explosives and Other Dangerous Articles". The Interstate Ccnnreroe Commission therefore regulates its shipment by land, water, and rail. Boron trifluoride is classi- fied as a nonflammable compressed gas and stored and shipped in I.C.C.- approved compressed gas cylinders. Personnel handling boron trifluoride should wear chemical safety goggles and rubber gloves. Gas masks approved for acid gases or masks with an independent oxygen or air supply should be available in case of emergency. The cylinders used for boron trifluoride should be pretested for leaks with dry air and aqueous ammonia. Leaking con- tainers of boron trifluoride which cannot be corrected should be discharged in a hood and techniques for disposing acid gases utilized. Boron trichloride is classified by the I.C.C. as a corrosive liquid and is also considered "a dangerous article" in transport. On contact with water or moist air it releases hydrochloric acid so chemical goggles, rubber gloves, and rubber aprons should be used in handling. Leaky containers which cannot be corrected should be disposed of using hood procedures for the disposal of acid gases. Diborane is classified by the Department of Transportation as a "Class A" poisonous and flammable gas. Diborane and the higher boranes are classified as "dangerous articles" in transport. They are shipped in cylinders pressurized with a diluent gas such as hydrogen, argon, nitrogen or helium. Diborane is highly unstable so no more than 0.1 kg can be shipped in a cylinder. To dispose of diborane the gas is fed into the bottom of a small vessel containing water. The water-diborane reaction produces hydrogen and boric acid. Procedures for shipping organo-boron compounds vary with the particular compound involved, amyl borates when contacted with water produce phenols so they are treated as corrosive chemicals. Lower alkyl borates are flammable methyl, ethyl, and butyl borates have flash points of 0, 32, and 94C respectively, and must be stored in approved areas. Other compounds, such as hexylene glyool diborate, offer no hazard and may be shipped or stored in any convenient manner. ------- W/AR INC. 1-36 Organic boron-oxygen compounds readily hydrolyze so they should be stored and transferred in an inert atmosphere. Usually glass containers are used for shipping small quantities; and steel cans,, drums, or tank cars are used for bulk iterns.(5) ------- 'KR/AR IMC, 1-37 V. ENVIRONMENTAL CONTAMINATION Boron is a ubiquitous element, generally occurring at concentrations of 10-30 ppm in soils, approximately 0.1 ppm in surface waters and about 4.5 ppm in sea water. Departures from these norms occur only in the very limited areas where natural boron sources are concentrated, such as in certain arid regions of California. Air monitoring data do not measure boron concentration as there is no evidence that it is present in the atmosphere to a significant (9) degree. In a relatively few areas there is concern about boron concentration. In irrigation waters the boron limit is set at 1.0 ppm. Nuclear reactor materials cnn tolerate boron only in bare trace amounts. There is also con- cern about boron concentration in processes where boron dust may be excessive, such as in the mining and handling of borax ore. A. From Uses Virtually all boron-containing materials and products requiring boron compounds in their manufacture constitute potential sources of boron contamin- ation. Little is done to check the boron content of surface .and river waters in the U.S. Through the use of boron compounds in detergents and other products, the boron concentration in surface waters can be expected to increase. Since sodium perborate is widely used in Europe in place of the American-type of chlorine-based bleach, the trend toward a build-up of boron concentration in surface waters should be more pronounced there. By following the buildup of boron in European waters it may be possible to establish the point where the (2) agricultural ecology of the U.S. will be upset. This treno would not be affected by sewage treatment since con- ventional sewage treatment removes little or no boron. Boron is ingested in the normal human diet, primarily from fruits and vegetables, at the rate of 10 to 20 my/day and excreted at the sane rate with little or no accumulation in the body. Boron in sewage is present as undissociated boric acid. ------- f4/M 1. Emissions to the atmosphere (including from production). Although the incidence of boron and boron compounds in the at- mosphere is quite limited, such emissions are known to occur and may be of local concern even if not sufficiently widespread to constitute an environmental pro- blem. Recent analysis of this problem considered potential sources of boron emissions. Emission factors have been determined for individual sources, by using: (1) direct observations and plant processing and engineering data; (2) literature; (3) observations of plant operators and others knowledgeable in the field; (4) calculations based on process data; and (5) analytical results where available. Based on the emission factors oa Table & and the 1972 use figures, (6) estimated emissions to air are given in Table 7. Details of boron emissions from use pattern are given below. Glass - The principal sources of particulate matter in the furnace exhaust gases are raw materials entrained in combustion gases and materials from the melt. Particulates expelled from the furnace are the result of many physical and chemical reactions that occur during melting. One factor which appears significant is the furnace production rate - as the latter is increased the quantity of particulates increases disproportionately. Ceramic Goatings - The principal emissions of boron from the production and use of ceramic coatings occur during the manufacture of the frit. 'ine smelting operation causes the most significant dust and fume emissions. There are also dust emissions from handling the raw materials as they are re- ceived, stored, measured, and mixed prior to charging the smelter. The atmos- pheric emissions of boron during frit smelting consist primarily of oxides in vapor form and in particulates. The magnitude of emissions varies considerably depending upon the amount of boron in the charge, the combination of ingredients, and the type of smelter. Agriculture Chemical - Emissions to the atmosphere occur principally when the materials are applied as sprays or dusts. Too many factors are in- volved (air movement,.drop size, nozzle type, etc.) to give an accurate estimate of emissions. Soap sand. Detergents - Boron compounds in the particulates emitted to Uie atmosphere arc refjorted to be sodium perborate, sodium tetraborate, and sodium borohydride; the particle size ranges from 1 to 10 microns. ------- "iK INC. 1-39 Table 6. Air Emission Factors for Boron Mining Processing End product uses of boron Glass manufacture Ceramic coatings Other emission sources Coal Sewage and sludge 0.5 kg/netric ton boron mined 14 kg/tnetric ton boron processed 35 kg/metric -con boron processed 40 kg/netric ton boron processed 9 kg/1,000 metric tons coal burned 28 kg/1000 metric tons sewage and sludge burned Table 7. Air Emissions of Boron by Source, 1972 Source Mining Processing End Product Other Sources Source Group Glass Ceramic Coating Agricultural Chemicals Soap and Detergents Miscellaneous Coal Sewage and Sludge Emission—Metric Tons 91 2,400 1,000 472 1,800 13 500 4,250 18 ------- KH/AR INC. 1-40 2. Amount entering waters and earth The major source of boron entering U.S. surface and ground waters arises from the use of boron-oontaining laundry products. 'iMs source, all of which may be assumed to enter the environment shortly after production, amounts to 15 per cent of the domestic consumption (which is roughly half of the total production). Thus, based on about 600,000 mt total production in 4 1972 as B-0^, approximately 1.4 x 10 mt of boron may be considered to enter the water per year through the use of boron-containing laundry products. Direct application to the land or crops as fertilizer or herbicides accounts for about seven per cent of domestic usage. This may also be con- sidered as entering the environment immediately upon production. Again, based on 1972 production, approximately 7 x 10 mt of boron appears to enter the environment per year from this source. Soros of this was included on Table 7 in air emissions. B. From Production 1. Mining Mining of borax using explosives and its subsequent shipping and handling created a serious dust problem. A three-year, $10 million program to cut down dust emissions at Boron, California was concluded in 1972. Nevertheless, (4) the operation is still not satisfactory and efforts to improve it are continuing. ' There are no detectable emissions in connection with the operation at Searles Lake. 2. Processing The primary emission from the processing of boron is sodium borate in various degrees of hydration, primarily from 1 to 3 moles of water. Boric oxide, boric acid, and sodium pentaborate are also enitted as these compounds are being produced. Particulate sizes range from less than 1 to 45 microns. Boron emissions vary considerably from plant to plant, ranging from 100 to 2000 mgAg of product. ------- KR/AR /NC. The major industrial waste in the boron-related industries appears to arise in the sodium borate effluent from B^O, manufacture. This amounts to about 400 kkg per year as boron. Phosphate rock contains 20-100 ppm boron, but even at a total phosphate rock production of 120 x 10 mt per year and an average boron content of 50 ppm, the boron effluent (water-borne or landfilled) from this industry amounts to only a few metric tons per year. C. Inadvertent These items are considered contaminators only in view of the special applications involved. Boron content of the materials used for construction and the chemicals used in nuclear reactors, for example, must be extremely low. This is because of the high atomic cross section of boron for thermal neutrons. In sone cases boron must foe removed from water used in the production of nuclear reactor materials. Sea water being used for magnesium oxide production as a refractory material and magnesium chloride brines being processed for magnesium metal when used in connection with nuclear reactors are prepared in this manner. Kunin of Rohm and Haas has developed a boron-selective ion-exchange resin which is available commercially as Amberlite I RA-943. In the case of irrigation water, a standard of 1 ppm boron has been established. Normally this limit is attained through dilution with other waters. The manufacturers of the Amberlite IRA-943 resin hc.ve made recent improvements and now claim that deboration of the average irrigation water can be effected at costs "well below 3 cents per 3.8 cu. m. ' D. Total Amounts Entering Environment per Year Total boron released to the environment based on 1972 production and use figures may be summarized by: ------- M/AR INC. i-42 Source Amount (metric ton) Laundry Products . 14,000 Agricultural Chemicals, Fertilizers Mining and Processing Glass and Ceramics Combustion of Coal Miscellaneous Total Of the estimated total of 32,000 mt per year, most ends up in the waters because of the relatively high solubility of all the compounds. ------- mjAR INC. MS VI. MONITORING AND ANALYSIS A. Monitoring Monitoring data on the boron content of U.S. waters is limited. For this reason, results of a survey conducted in Europe is cf interest. A study was made for the National Swedish Environmental Protection Board, Uppsala, of boron in Swedish and Norwegian fresh waters. The study began in 1970 and took a year to complete. Regional variations due to differences in geology, land use, and population density were found, but there were only small seasonal variations. The enrichment of boron in aquatic plants was very sinall conpared to that of phosphorus and nitrogen. Sewage water showed a lower boron content than that of England. 'Ihe mean concentration of boron in Swedish and Norwegian fresh waters was low and close to that of other rivers of the world. The median boron content in 355 sarrplcs was approximately 12 micrograms/liter. ' D. Analysis 1. Determination of boron in water. Colorimetric and spectrographic methods have been used to analyze boron in fresh water in concentrations of less than 1 ppm. One of the most use- ful methods is "the identical pH" method with which a sensitivity of +_ 0.05 ppm boron can be obtained if a 500 ml sample is used. With this method separation or special sample treatment is not required. Detection of the boron by electro- metric instead of coiorimetric technique is recommended. For use with more than 1 PJOT boron, the standard mannitol borate procedure may be used after removing (14) intcrfcrring bicarbonate and netal ions. 'lhc analysis of boron in sea water represents a special case. A high cbcjrce of precision and accuracy are required because the ratio of boron to toal salt content is almost constant throughout the world. Only bicarbonate ion removal is required for the mannitol borate procedure. Polynydroxy organic (14) natter causes low results by complexing the boron. 2. Determination of boron in plants and biological materials. The boron analysis in plants is important for avoiding toxicity on the one hand and deficiency on the other. The ppm range is normally involved and the best techniques are coiorimetric and spectrographic. The treatment of ------- 1-44 the sample must be care fully carried out to avoid both loss of boron and contamination from borosilicate glassware. Almost all methods for boron analysis in biological materials involve ignition of the sample which may cause some loss of boron. Contamination with boron from the ovens may be experienced. Spectroqraphic and flame photometric procedures are more convenient than those (14) requiring extensive treatment after ashing. 3. Analysis of available boron in soil. Boron is analyzed in soil by boiling a 1:2 soil to water suspension for five minutes in a reflux condenser. The solution phase is separated to determine boron. 4. Detection of boron in airborne contaminants collected in air filters. To detect boron in airborne contaminants collected in air filters a small portion of the filter is rolled up into a cylinder and placed in a hollow graphite electrode. This portion of the air filter is directly excited by the condensed spark discharge in an oxygen atmosphere. The sample bums, exciting the spectra. A photographic recording is used to interpret the spectra and, when improved precision is required, line intensities are measured with a microphotometcr. The limits of detection are 0.1 to 1.0 micrograms. The results obtained from the rapid emission spectrographic method are compatible with results obtained with the more conventional technique of ashing the filter, mixing it with a spectrographic buffer, and exciting it in a D.C. arc. 5. Analysis of boron in air by coloriiretry. in the coloriirEtry method of analysis, about 1,000 liters of airh passes at a rate of two to three liters per minute through four collecting tubes chilled in a methanol-dry ice bath. The collected boron is dissolved in 10 ml. water and added to 1.5 ml. of curcumin reagent solution. The solution is evaporated until the odor of phenol disappears. The residue is dissolved in 10 ml. cthanol and absorbance is measured at 548 millimicrons. ------- 1-45 VII. CHEMICAL REACTIVITY A. Environmental and Use Associated^ Reactions Borax solutions, usually a buffer mixture of sodium borate and boric acid, are widely used for pH control in: cutting fluids, detergents and soaps, electroplating, dyeing of natural and synthetic fibers, photographic processing, Pharmaceuticals, cosmetic preparations, plastics manufacture and vitreous enamelling. The pH value of a O.lM solution of borax is 9.2. Na~B 0 . 10H_0 -*• 2Na + 2B(OH) ~ + 2H^BO_ + 3H_O Boron trichloride and boron trifluoride hydrolyze rapidly on con- tact with water to form boric acid and the corresponding hydrochloric or hydrofluoric acid. The manufacture of boron-containing combined fertilizer by the direct action of sulfuric or nitric acid on phosphate rock with fluoride impurities results in a product containing a boron-fluoride complex similar to potassium fluoborate. In Switzerland's Rhone Valley, apricot orchards and vineyards using a certain fertilizer showed high fluoride content in the plants and typical (18) fluoride-induced necroses of the foliage. The effect of the environment on diborane and higher boranes is given in Table 8. In the case of pentaborane, conflicting data are reported. B. Aspects with Biological Implication The complexing ability of the boron atom is considered to be the key explanation of its essentiality to higher plants. The exact mechanism of its action is still unknown, and is the subject of much research. One theory is that the complexing action of boron facilitates the transport of organic com- pounds such as sugars in plants. Other biological inplications under consider- ation as an explanation of the effect of boron on plants are: its effect on plant enzymes, the interrelationship between boron and plant hormones synthesis (plant growth regulator response), nucleic acid biosynthesis relationship to cellular growth and differentiation, cell wall formation and pectic synthesis, phenolic acid biosynthesis and liquification, increased carbohydrate metabolism and respiration, cell wall and membrane metabolism, and pollen germination. All ------- Table 8. Relative Stabilities of Boron Hydrides (5) Compound diborane tetraborane pentaborane hexaborane decaborane Room temperature, no oxygen fairly stable, 10% deoom- ppsition in presence of hydrogen fairly rapid decomposition (a)stable for years; decomposes slowly at 150 C (b) begins to decompose within 1 hr deocnposes slowly very stable; can be heated for some time at 150 C; noticeable decomposition at 170 C Room temperature, presence of air spontaneously flammable above 40 C and at room temperature in presence of impurities not spontaneously flam- mable if pure spontaneously flammable quite stable; not spon- taneously flammable very stable; not spon- taneously flammable; explodes in oxygen at 100 C Presence of water hydrolyzes instantaneo"usly and almost quantitatively at room temperature hydrolyzes completely within 24 hr at room temperature hydrolyzes only at elevated temperatures hydrolyzes rapidly hydrolyzes completely only at elevated temperatures hydrolyzes very slowly at room temperature ------- / KR/AR INC, M7 of these effects ot boron on plant growth probably play some role in its (19) benefits. The primary effects, however, have not yet been determined. ------- ER/AR INC, i-48 VEIL BIOLOGY A. Absorption, Excretion, Growth, and Nutrition 1. Humans The average concentration of boron in the blood and urine of 154 American males of various occupations and ages is 9.85 ygrams per 100 grams ns t] (21) and 7.15 mg per liter, respectively. The skeletal tissue contains the highest boron concentration (0.90 ppm) of all body tissues analyzed. Sinoe boron is widely distributed in fruits and other foods, (22) humans constantly ingest and excrete this element. Conflicting information as to the transcutaneous absorption of boric acid from talc exists. No increase in boron was observed in the blood of infants maintained on a regimen of boric (22) acid dusting powder "ad. lib" for a year. , In another study, children using baby powder containing three per cent boric acid had significantly more boron (23) in their blood than the control group. A fatal case of transcutaneous absorption of boric acid occurred in a seven-month-old male infant being treated for dermatitis with three per cent boric acid powder. The boron concentrations in the bile, intestinal contents (24) and spleen were 20.2, 18.3, and 18.2 mg %, respectively. After vaginal administration of 40g of boric acid, the serum boron level rose from 0 to 750 ygrams % within 48 hours in a patient with healthy epithelial tissue in the vagina and on the portio, but up to 2150 ygrams % in a patient with vaginitis and erosion of the portio. In patients with vaginitis receiving daily 20g doses of boric acid, the serum boron was a maximum of 850 (25) iicjrams % after five days of treatment, and 1900 ygrams % after seven days. Phenylmercuric borate was not absorbed by the epidermis or cutis (26) in man or rats when applied without a protective dressing. 2. Nonhuman Mammals Boron compounds are preferentially accumulated by the brain and (27 28 29) tumor tissue of animals. ' ' Localization in the brain can be ration- alized in terms of one parameter obtained from the waterroctanol partition co- efficients. Localization in the tumor depends also upon the electronic para- (29) meter. ------- >M/AK INC. M9 An aqueous jelly and two oleaginous ointments containing less than three per cent boric acid were applied to the skin of anesthetized rats, and boron absorption was monitored by measuring boron in the urine. Little or no increase was observed after eight hours if the application was made to intact skin, but when the ointments were applied to damaged skin, four to eight times the control level of boron appeared in the urine. Only 25% of the original boron remained in the ointment after treatment of an enclosed area of damaged skin, but 98% remained in the jelly. In the urine, 25% and 1%, respectively, of the total boron from the jelly and ointment applications were recovered, in- dicating that a high rate of absorption with inadequate excretion occurred with the aqueous jelly, but the slight absorption from the ointments was followed by rapid excretion. ' Sodium me thy Iterate (0.2g B per kg in 2% physiological serum) was injected into pregnant rats on the 18th and 19th days of gestation. Boron pene- trated into the amniotic fluid more rapidly on the 19th day than on the 18th, and the diffusion of boron into the amniotic fluid increased as gestation progressed. ' The amount of boron in cow's milk varies with the amount of boron in the feed. About one quarter of the total boron is in the cream, the re- (32) mainder in the skim nalk. 3. Plants As shown in Table 9, nutritional requirements for boron vary greatly. Boron deficiency in plants induces severe symptoms. These include cessation of root and leaf growth, necrosis of leaf primorcfia and primary root tips, spongy mesophyll layers of leaves, necrosis of stem and leaf phloem, bark splitting, reduced pollen germination and pollen tube growth, reduced fluor- escence, abnormal cell differentiation, reduced growth, and death if the de- ficiency is not corrected. Normal growth and development usually resumes when boron is added to the growth medium. Boron is absorbed by the roots of the plant and translocated to the leaves, where it occurs in highest concentration. In a study on sunflowers, ------- KK/AK INC. i-so Table 9. Diagnostic Criteria for Boron Nutrition of Field and Vegetable Crops Based upon Hot Water Extraction of Soil Boron (169) Boron Content of Soils for Optimum Growth 0.1 iigram of B/gram 0.1-0.5 ygram of B/gram 0.5 ygram of B/gram Small grain Tobacco Apple Corn Tomato Alfalfa Soybean Lettuce Clovers Pea and bean Peach Beets Strawberry Pear Turnips Potato Cherry Cruciferae Grass Olive Asparagus Flax . Pecan Radish Cotton Celery Sveet Potato Rutabaga Peanut Carrot Onion ------- I wjAR IMC. 1-51 boron accumulation required nitrogen in the nutrient solution. Once in the leaves, boron was not transported to other parts of the plant.' ' As boron in the nutrient solution increased, boron in the leaves increased in the carnation, Dianthus caryophyllus, but not in the reproductive organs. Figure 8 relates boron concentration in plant tissues to the concentration in soil solution. Similar results were observed in studies on tobacco, (36) (37) onions, and birch. Borate absorption by excised sugarcane leaves occurred in a two stage transport system. The first stage is a rapid, reversible influx into the mesophyll cells of the leaves, followed by a slower, irreversible accumulating phase. Stage two consists of three absorptive reactions. The first two re- actions involve active transport of borate across the cell membrane; the third carries the borate across tie vacuolar membrane. Calcium is essential for maximum boron uptake, and all three reactions are inhibited by hydroxide ions. factions one and two are apparently coupled to the electron transport system. /TO\ The third mayibai linked to ioxidative phosphorylation. Phenylboric acid, which is split into phenol and boric acid by horse radish peroxidase and oxygen, promotes the lengthening of roots in Phaseolus vulgaris primarily by stimulating the rate of cell elongation. Phenylboric acid also stimulated the initiation of xylem development and the full elongation of (39) epidermal cells at a greater distance from the apex than in controls. 4. Microorganisms The thermostability of Paramecium caudatum at 40 C was increased by the addition of 0.01 and 0.05 per cent boric acid to Losina-losihsky saline solution at a pH of 7.0-7.2. At pH 6.4 or lower, however, the addition of boric (40) acid caused a decrease in the thermal stability of the ciliates. B. Biochemistry 1. Humans No requirement for boron in humans is known. Since boron is ex- (41) creted from the body very slowly, accumulation in the tissues is likely to occur. The long term effects of drinking water high in boron (4,6 mg per liter) on the ------- 1-52 2000 r 1500- (0 1000- 500 r 5 10 15 20 PPM BORON IN SOIL SOLUTION 25 Figure 8 Boron concentration in plant tissues related to concentration in soil solution ------- 'KR/AR INC. 1-53 gastrointestinal tract were studied in 288 persons. In people drinking high-boron waters, the incidence of hypoacidity doubled in adults, and enterokinase activity in feces of children was 25% of that in persons drinking low boron water. ^ • ' Borates cause nonoompetitive inhibition of nonspecific ester hydrolysis by chymotrypsin, perhaps by interacting with the free electron pair on an imidazole moiety at the active site. Changes in ionic strength (0.06 - 0.4) do not significantly affect the inhibition, but changes in pH do. Aryl and alkyl boronic acids act as competitive inhibitors of 6-chymotrypsin. The ionic borate group apparently interacts with histidine and/or imidazole residues at the active site, and the organic residues interact with hydrophobic sites. n-Hexylborortic acid had the strongest inhibitory effect of the n-alkylboronic (45) acids studied. 2. Nonhunan Mamnals Boric acid and its salts affect diverse metabolic pathways in animals. In rats fed a low-borate diet (0.001 ppm boron), liver RNA synthesis as measured 14 14 by C-orotic acid and C-uridine incorporation is stimulated by the intra- peritoneal injection of borate. Feeding of 1 ppm boron diminished this effect. The activity of rat liver DNA-dependent RNA polymerase was stimulated in vitro by 10 to 10 M borate, but higher concentrations were inhibitory. ' Inhibition of oxygen utilization in the brain by boric acid and sodium metaborate can be significantly alleviated by the presence of glucose and pyruvate (28) in the median. In the rat, boric acid was found to inhibit glucose-6- phosphatasc, phosphoglucomutase and phosphohexose isomerase in the liver, brain and kidney, except that kidney phosphoglucomutase was stimulated by borate. iterate competitively inhibited glyceraldehyde phosphate dehydrogenase in rat and guinea pig liver homogenates, causing fructose-6-phosphate and fructose-1, 6-diphosphate to accumulate. Lactate dehydrogenase was not affected by borate. Anaerobic glycolysis in guinea pig erythrocytes was inhibited by addition of (49) borate to the blood, and rnethemoglobin increased substantially. The in- hibition of methemoglobin reduction by borate, which is greater in man and pigs than in rats, guinea pigs and rabbits, may be alleviated by the addition of (49) NADU,,. The loss of activity may occur via glyceraldehyde phosphate dehydro- ijunnse inhibition. The ratio of NAD:NADH2 increases in the presence of borate, ------- 'Mi/Alt INC. [-54 indicating restricted generation of NADH». The NADPH system was not as (49) greatly affected by borates as the NADH system.v ' Changes in the EPR spectra of heire and non-heme iron complexes (50) were observed in livers of mice with bone acid intoxication. A sharp decrease in the electron spin resonance signal of pigment 450 in the respiratory chain of microsomas was also noted. The addition of 2-3 mg per liter or more of boron to the drinking water of dogs resulted in decreased gastric secretions, free and total gastric hypoacidity and inhibition of fecal enterokinase activity. In rabbits re- ceiving daily gastric administrations of 100 mg per kg calcium borate, a slight decrease in total serum lipids and free sulfhydryl groups in the serum was observed. Inhalation treatments (120-150 mg/m /2 hr/day for 10 weeks) resulted in an increase in urinary excretion of nitrogen compounds. The urate oxidase activity of ammonia extracts of ox kidney acetone powder was increased 290% in 3-100 nM borate buffer. The borate effect was chiefly due to stabiliz- ation of the enzyme. Borate inhibited the adrenalin activation of dog liver dephospho- phosphorylase. A mixture of borate and L-serine inhibited Y-glutamyl transpeptidase in various guinea pig tissues (kidney, liver, spleen, uterus, 14 lung, intestine, heart, brain and muscle). Intravenous injection of j-lr- C- cj.l utamyl-a-naphthylamide as substrate accompanied by borate-lr-serine treatment resulted in n decrease in (i-naphthylamine and transpeptidation products and (54) increased amounts of substrate in the urine. Tetraphenylboron (TPB) strongly inhibits protein synthesis. 14 In isolated rat liver cells, TPB administration reduced oxidation of u- C-glucose, 14 glycogen concentration and the effect of insulin. The incorporation of C- leucine into protein was lowered, as were the activities of glucose-6-phosphate phosphohydrolase and lactate dehydrogenase. In rat liver mitochondria, TPB exerted a powerful uncoupling of oxidative phosphorylation. Reversed 32 electron transfer, calcium transport, and ATP- P exchange were inhibited. TPB stimulated ATP hydrolysis. Sodium TPB inhibited rat liver aminopeptidase D as evidenced by the decreased rate of hydrolysis of N-L-arginyl-2-naphthylamine. ------- 'KR/AK INC. 1-55 The antitubocurarine action of TPB irost closely resembles that of tetraaranionium triethylcholine and phenol. In the biventer cervicis muscle of the chick, TPB increases acetylcholine release and also exerts a weakly i exe (60) (59) anticholinesterase effect. TPB exerts a blocking action on acetylcholine- sterase in guinea pig smooth muscle. Organic derivatives of boric acid exert a wide variety of effects on diverse tissues. o-Methoxybenzene-boronic acid exerts a peripheral hypotensive action, which is not accompanied by a hypnotic effect. This compound stimulates an increase in cardiac contraction and increased cerebral blood flow. ' Pentaerythritol di-(p-methylbenzene boronate), p-methylhenzeneboronic acid, and methyl-p-itethylbenzeboronate are not hypnotic, but enhance the hypnotic effects of chloral hydrate and hexobarbital. The first drug causes an increase .i.n arterial blood pressure, but it acts as a peripheral dilator and depresses cardiac contractile activity, and inhibits the hypertensive action of exogenous and indirect amines. o-,m- and p-tolylboronic acids become localized in the cerebrum; for example, one hour after intraperitoneal infection of sodium- o-tolylboronate, the boron content in the cerebrum was six times that of the blood. 'J-4y^ Spasmolytic activity of seven arylboronic acid compounds was studied in isolated guinea pig duodenum. The substitution of one hydroxyl group in boric acid by a methyl-benzene group conferred spasmolytic activity. o-Methoxy- benzeneboronic acid differed from other derivatives in that it e>aarted a specific musculotropic spasmolytic activity and no neurotropic activity. ' Some of the derivatives exerted an antiserotonergic effect on the uterine tissue of virgin t (61) rats. Itorancs produce extensive changes in tissue amino acid levels in (62) the rat by inhibition of pyridoxal-dependent enzymes such as aminotransferasesv ' ' and histidine decarboxylase.^ ' Tissue histamine levels were greatly reduced by injection of decaborane (15 ing per kg). Histamine was reduced in liver, kidney, stomach, brain and urine, but not in heart. Brain levels fell 50% and were still depleted one week after injection, whereas rat stomach de- pletion lasted only 48 hours. Changes induced by pyridoxine deficiency in rat are accentuated by intraperitoneal borane injection (20 mg per kg): ' ------- i-56 However, aspartate aminotransf erase (AAT) ac±ivity is greater in the tissues of pyridoxine-deficient rats, and decaborane does not significantly affect it. Decaborane does inhibit MT in the liver, heart, brain, and kidneys of normal rats. Lactate dehydrogenase is moderately inhibited by decaborane in the heart and kidney of normal and pyridoxal-deficient rats and in the brain of normal rats.(63'66) Borohydrides readily reduce the double bond of the Schiff base formed from cytochromc oxidase. ' 3. Nonmammalian Vertebrates Boric acid produced malformation of the posterior extremities of the chicken embryo, possibly by interfering with the process of extension of the /gq\ collagen fibers in the cartilage. Vitamin C was useful in protecting the tadpoles of Rana temporaria from the toxic effects of phenylmercuriborate. p-Nitrobenzene[N]diazonium fluoroborate and its trimethyl deriva- tive are potent inhibitors of the carbamyl-choline-induced depolarization of the electroplax and also of acetylcholinesterase. These organoboron compounds are believed to form covalent bonds with the acetylcholine receptor and esteratic sites on the electroplax. 4. Plants The essentiality of boron to higher plant reproduction, growth and metabolism is firmly established. Boron deficiency symptoms are browning and spotting of leaves, chlorosis, necrosis and finally death. No single specific. role has been found for boron; in fact boron apparently exerts many effects on a variety of metabolic sites. The following summary of boron biochemistry in plants is primarily based on a review article by Dagger. ------- 'RR/AR JNC. 1-57 Boron apparently controls plant metabolism by inhibiting certain key enzymatic reactions in plants. Several sites of inhibition occur in carbohydrate metabolism. Effects of boron deficiency which may be ex- plained via effects on carbohydrate metabolism are increased starch accumulation, increased pentose-shunt activity, leading to an accumulation of polyphenol compounds and an increase in phenolic acids and indoleacetic acid (IM). An increase in cell wall products of altered composition were also observed. Reproduction and growth are adversely effected. Starch accumulates as a result of alleviation of borate in- hibition of starch phosphorylase, reducing the amounts of free reducing sugars. Uninhibited activity of UDPG transglycolase, phosphoglucomutase permit increased hexose metabolism via the pentose shunt. The products from this cycle are con- verted into polyphenolic compounds, which are normally complexed by borate and not further oxidized. Under conditions of borate deficiency, oxidative enzymes (including catechol oxidase, xanthine oxidase, horse radish peroxidase, tyrosinase and alcohol dehydrogenase) convert these compounds to toxic polyphenolic acids. IAA accumulates due to its reduced oxidation due to the presence of other poly- phenolic substrates. Reduced polymerization of phenolic compounds into lignins also occurred. Nucleic acid metabolism and protein synthesis are also disrupted by boron deficiency. Boron controls ENAase activity by inhibition or seques- tration. In boron deficient plants, RNAase activity is greatly increased and RNA content greatly reduced. DNA synthesis, RNA synthesis, and aminoacyl tRNA levels are maintained, but rate of protein synthesis is decreased, and an increase in free amino acids and total nitrogen content in plants occurs. Growth and reproduction are almost certainly aberrant in boron-deficient plants due to inadequate protein synthesis resulting from disturbed nucleic acid metabolism. In boron-deficient plants, ATPase activity doubles and ATP levels arc quite low. The reduction of available ATP also prevents the normal pro- gress of energy-requiring synthetic reactions, including chlorophyll synthesis and protein synthesis. ------- WR/AR 1-58 Boron promotes the uptake and translocation of carbohydrates and reduces nitrogen absorption in nitrogen sufficient plants. Xylem proliferation is stimulated by boron. Borate ions in the itBdium clearly inhibited chloride absorption, but not iodine uptake, in Lemna minor. Boron fertilization reduced water loss in sugar beets throughout the entire vegetative period, and the addition of lime prevented the toxic effect of (74) too much boron and actually increased the boron requirements. The accumulation and disposition of thiamine to the ootyledonous shoots of lupine (75) was facilitated by boron. 5. Microorganisms No nutritional requirement for boron has been established in microorganisms, but borates added to the medium produce definite metabolic effects, primarily inhibitory and toxic. In yeast in sucrose solution, boric acid favored anaerobic res- piration at the expense of aerobic. The number of cells rich in glycogen decreased with one to two per cent boric acid, but little effect was observed with four per cent probably due to a larger proportion of the more active Cjc\ orthoboric acid in more dilute solution.v Fructose-1, 6-diphosphate and ADP accumulated in boron-toxic cultures of Saccharomyces cerevisiae, whereas phosphoglyceric acid and ATP levels decreased. This effect was explained by (38) the uncompetitive. inhibition of aldolase by boric acid. Yeast alcohol (77) dehydrogenase was also inhibited by borate. Borate buffer also influenced the production of 5'-nucleotides via the autodegradation of intracellular PNA in yeast. (78) In fungi, o-diphenol oxidase was competitively inhibited by borate. (46) Borax inhibited the formation of HCN by a normally cyanogenic isolate :id c (38) (79) of the snow mold of alfalfa. Boric acid eserted a toxic effect on fungi by preventing O~ uptake and 00- evolution. Erythromycin, produced by Streptomyces, is known to lose its biologic activity in borate buffer solution by the formation of complexes in- (80) volving dihydroerythrcmyciji. Boric acid prevents the incorporation of separately-formed sugars into erythromycin by complexation, and also causes the synthesis of structurally-changed sugars which result in biologically inactive . (81) erythromycin. ------- 'i:\\JAR IMC. 1-59 Sodium borate inhibits the decomposition, presumably by micro- (82) organisms, of two protein hydrolysates attractive to the Mexican fruit fly. Borate sensitivity in staphylococci correlated well with lysozyme and a-toxin (83) production in the coagulase-positive strain. Borotungstate had an inhibitory effect on RNA-dependent DMA polymerase of mouse oncogenic viruses and, on RNA-dependent RNA polymarases of various RNA viruses. C. Therapeutic Uses 1. Humans Doric acid and borates, as well as complex organic boron compounds, have a variety of medical uses. Saturated, three per cent and two per cent solu- tions of boric acid inhibited the growth of Salmonella typhosa, Escherichia coli, Staphyloooccus aurtsus, and Proteus vulgaris for over a week, although no bacter- TEST icidal activity was observed. Boric acid is a useful preservative of urine specimens. A three per cent boric acid solution preserves the urine specimen t fifi} for up to 24 hours. Of 235 strains of coagulase-positive £>. aureus, 221 (94%) were inhibited by 1.5 x 10 M sodium borate. Only 6 out of 57 (10.5%) of the coagulase-negative strains were inhibited at this concentration, Pour of (83) the six strains were food poisoning strains, and one was a hospital pathogen. The antifungal action of boric acid is increased in the presence of sorrc polyhydroxy compounds, including nontoxic agents which .conplex with boric acid such as lactic acid and mannitol, and toxic agents, such as salicylic acid, oxalic acid and pentachlorophenol, which complex with boric acid and exhibit strong synergism. Penicillium careicolun, P. expansum, P. glaucum (88) Aspergillus niger, and Mucor racemosus were studied. Phenylmercuric borate (0.05-0.06%) has been shown to be quite use- ful in treatment of various mycotic infections (dermatophytes, tinea cruris, (c) crythrasma, pityriasis versicolor), especially of mold and yeast. Zyma (0.06% phenylmercuric borate) and Exomycol gel (0.05% phenylmercuric borate) (89 90) arc two marketed preparations. ' Phenylmercuric borate (0.04%) combined (91) with 3% hexachlorophene in a bland emulsion serves as a good surgical disinfectant. ------- I VR/AR INC. i-60 The antimicrobial action of Remanex, a canmsrcial mixture of the two com- pounds, was much more effective upon Streptomyces sp. than either of its (92) components alone. Orthoanisyl boric acid, exhibiting a low toxicity and readily eliminated, serves as a nonhypnotic sedative which reinforces the action of (93) hypnotics and anticonvulsants. ' Pentaerythritol di-(p-methylbenzeneboron- ate) acts as an anticonvulsant for Metrazol and electroshxk seizures but has no effect on strychnine convulsions. Tumor-specific boron-containing compounds have been evaluted for use in tumor therapy by neutron capture techniques. 3-amino-4-carboxybenzene boronic acid, m-boronosuccinanilic acid and sodium perhydrodecaborate, * ' /QC\ as well as boron-labelled antibodies and elemental boron, ' have been tested as neutron targets. An 0.5% solution of levepinephrine borate enhanced the hypotensive response to pilocarpine. Maximum response occurred with a 4% solution. 2. Nonhuman Mammals A three percent solution of boric acid was the most effective (97) therapeutic agent in treating Thelazia infestations in 250 calves. ' Phenylmercuric borate at three concentrations (0.125%, 0.25%, and 0.50%) was effective in inhibiting dental caries in fissures and smooth (98) surfaces of teeth in Osbome-Mendal rats fed a high-sucrose diet. Borotungstate was inhibitory to mouse sarcoma-leukemia virus (99) infection of cultured cells. Absolute control of an experimental sarcoma in mice was attained by boron thermal neutron interaction. 3. Plants Treatment with boric acid protects plants against insect and fungus infection. The two-toothed longhom beetle, Ambeodontus tristis, in sapwood kahikatea, Podocarpus dacrydioides, did not survive a treatment of 0.142% or more boric acid. Boric acid solutions greater than 1.09% were effective against several termite species: Nasutitermes exitiosus, Coptotermes lacteus, and C. acinaciformis. Boric acid was useful as a stomach poison in killing the wood-destroying larvae of Hylotrupes bajulus in wood not exposed ------- 1-61 to wax. ' When boll-weevils are fed B-boric acid and irradiated with neutrons, a ten-fold increase in mortality and tvo-fold increase in sterility occurred in the adults. The presence of McPhail traps baited with a cotton- seed hydrolysate and borax reduced infestation of navel oranges and mangoes by the Mexican fruit fly (Anastrepha ludem) by 68% and 98% respectively. ' Boric acid and borax are both cleared by the FDA for post-harvest use on citrus fruits as fungicides. An 0.2% solution of boric acid pre- vents attack of wood rotting fungi such as lyctus brunneus Steph, Merulius lacrymang, Coniophora oerebella, Lezites trabea, and Lentinus lepideus. Mold growth was completely inhibited by 2.5% boric acid or borax. Application of boron-calcium or boron-calcium naphthalene acetamide foliar sprays significantly reduced the number of cork spots per fruit in York Imperial apple trees. The number of spots on fruit flesh and peel decreased as the boron and calcium content of the leaves increased. Borax applications were effective in preventing Fames annosus (root rot) infection in several species of conifer. Dry powder applications prevented root rot in Jeffrey pine stumps and white fir stumps. The growth of mycelium was prohibited by 75 ppm borax; germination of conidia, by 65 ppm; and basidiospore formation at 90 ppm. Application of 660 ppm total anhydrous borax to oven dry wood of the loblolly pine (Pinus taeda) raised the pH of the wood from 4.8 to 7.6-8.1 and prevented the growth of Fomes annosus. Tetraborate application was only partially effective in controlling coppicing in teak (Tectona grandis L). A one per cent solution of borax was effective in inhibiting the growth of Penicillium oxalicum and Helminthosporum cyclops, the most active microorganisms infecting Egyptian canesugar. ------- 1-62 IX. ENVIRONMENTAL EFFECTS A. Environmental Content, Transport, Contamination Boron exists in several forms in the soil. Boron is present in organic matter, in various soil minerals such as tourmaline, and in the soil solution in equilibrium with boron adsorbed on the surfaces of soil particles. The bulk of the total boron comes from soil minerals, hence the soil boron content is primarily related to the parent material of the soil. Soils from marine shales are particularly rich in boron, with sedimentary soils next, followed by igneous. Small and variable amounts of boron are found in soil organic matter. This boron becomes available to plants as it becomes mineralized and redistributed in the soil-water system. In soils above the detrital cone of the Danube in Hungary, boron was shown to accumulate in the upper soil levels, which contained 1.67 bo 3.06 times the amount of boron found in the (182) parent material of the soil. The boron in soil solution and the boron adsorbed to soil minerals is in an equilibrium dependent upon the boron concentration of the solution (particularly the horate ion), pH, organic matter content, and the number of active adsorption sites per unit weight of soil. Although plants absorb boron directly from the soil solution, it is the adsorbed boron which provides a source of boron to maintain the soil solution level. The adsorption sites for boron are associated with broken silicon- oxygen and aluminum-oxygen bonds exposed at the edges of aluminosilicate metals, with surfaces of amorphous hydroxides such as allophane and hydroxyaluminum and iron aonpounds, with magnesium hydroxide coatings and clusters that form on the exposed surfaces of ferromagnesium minerals and micaceous, layer silicates in arid soils, and with sesquioxide coatings on the surfaces of clays. Volcanic ash soils adsorb the highest amounts of boron. ' Boron adsorption occurs independently of pH in the acid range, with increased adsorption in the alkaline range, and maximum adsorption at pH 9.0. These pH effects suggest that it is molecular boric acid that is adsorbed under acid conditions, while it is the borate ion which is adsorbed as the pH approaches 9.0. ------- / wjAK INC. 1-63 Boron adsorption takes place independently of concomitant adsorption of other anions. Adsorbed boron tends to leach relatively easily from soils. In a study of the heath podzol and gray-brown soils in Schleswig-Holstein, the low leaching of the heath podzol indicates the relatively high capacity of raw humus to bind boron. Water-soluble boron is usually determined by a hot water extraction technique or a saturation-equilibration method followed by vacuum extraction. Significant correlations were found between hot-water extractable boron and salinity,(185'186)organic matter content,(182/183/186/187) pH and fineness of soil texture. Liming of two acid soils with calcium carbonate decreased boron mobility(188) (34 189) depresses soluble soil boron reserves. ' Seasonal variations in the boron content of the waters of Sweden and were (191) Norway were small. Increased levels of boron were observed in rainfall in the southeastern U.S. during the winter months. In sandy soil, twenty pounds of borax per feddan is toxic to berseem. In loamy soil, fifty pounds per feddan is required to produce toxicity symptoms. Heavily calcareous soils offset the boron toxicity. In saline and alkaline soils, boron toxicity could be corrected by leaching and replacing sodium with calcium. The soil content of boron may not only be altered by application of boron-containing fertilizers, which leach to varying degrees, but also by airborne boron, presumably from human activities. In urban garden soils of Scotland, the water-soluble boron levels were two to three times the ' ash" (194) levels in arable rural soils. In "fly ash", boron (not manganese or aluminum) is the toxic substance to plants. In certain industries, such as boron carbide and boron fertilizer industries, workers are exposed to air pollution and aerosols which may produce a chronic health problem. ' ' The maximum permissible levels of calcium borate in the air in the industry should be four to six mg per m c • (52) of air. ------- 1-64 Due to CXT>P sensitivity to boron, the levels of boron in waters used for irrigation should not exceed the critical boron concentration for the (169 196) particular crop species as follows: ' ' Crop Species Critical Boron Concentration (ygram B/itil) Sensitive 0.3-1.0 Semitolerant 1.0-2.0 Tolerant 2.0-4.0 A serious criticism of this type of limitation is the lack of provision for soil type, irrigation.management and climate. Sources of boron introduction to waters are soil minerals, rainfall, industry, and sewage effluents. The majority of surface waters in the United States have boron concentrations ranging from 0.1 to 0.3 ygram B/ml.^1&9' in a study of boron content in rainfall in two sites in Mississippi and one in South Carolina, the boron concentration was 10 ppb, and the input of boron by rainfall amounted to 62.7-74.2 grams per hectare for a one year period. The Santa Ana River basin in southern California is a good example of the effects of urbanization on the water supply. The volume of return flow from irrigation is steadily decreasing while the input from municipalities is increasing. The waste discharge accounts for 0.75-1.50 ygram of B/ml depending upon the city and the season. As much as 50% of the boron in effluents originates from household use such as in laundry detergents. In limiting the inputs from sewage effluents, the downstream rainfall must be considered, as well as the type of soil. The hazard of boron is essentially eliminated if the effluent percolates through the soil. B. Bioaccumulation and Content 1. Human The average urine and serum levels of boron in workers from various occupations and geographical locations were: 9.85 yg per 100 ml of blood and 7.15 ug per liter of urine. The beta-hydroxyethy?. derivative of boron and its phosphate ester appeared to be strongly bound to tumor tissue and gave (198) vnry favorable tumor:blood boron ratios. ------- 1-65 2. Mamnals Boric acid accumulated in the brain after repeated inject- (27) ions. Boron, which appears to be a normal constituent of cow's milk, increased from 270 to 630 micrograitE per liter on the average in the milk of cows fed 300 mg sodium tetraborate per day for two weeks. The oon- (32) cent ration of boron did not vary with the amount of milk produced. About 25% of the total amount of boron in cow's milk was found in the cream; 75% in (32) the skim milk. 3. Plants The boron contents of plants depend not only on their taxon- (199) omic position, but also on the content of soil boron and degree of availability. On the ninth day after boron treatment in sand culture, groundnut accumu- lated excessive boron in the basal, mature middle and apical developing leaves (2.51, 2.86 and 2.62 mg per gram dry weight). Boron levels in 22 species of aquatic macrophytes from a reservoir ranged from 1.2 to 11.3 ppm dry weight. Boron uptake studies on the swamp plant, Typha latifolia, however, showed no significant correlation between boron in the soil and plant tissue levels. Boron concentrations in plants may vary with the season. 0.91) Typha latifolia exhibited maximum boron uptake during early spring growth. The leaves of the trees in an oak - hornbeam forest (Quercus petrae, Q. cerris, Carpinus betulus, Acer campestre, Comus mas, Crataegus oxyacantha and Ligustrum vulgare) accumulated boron and calcium up to three times the levels found in the . leaves in the spring. Disease state may affect boron accumulation. The boron content of a clubroot-sensitive cabbage cultivar was higher than in a clubroot-resistant one. As clubroot infection in the sensitive strain worsened, the boron content increased even more. In the resistant strain, however, the boron content in- itially increased slightly and then decreased during clubroot infection. Boron can affect the accumulation of other substances„ In dry matter from vineyards and apricot orchards in the Rhone Valley in Switzerland^ a fluoride content up to 600 ppm was due to a boron-containing combined fertilizer. A particular boron-fluoride chemical combination of unknown composition, but si.irii.lar to KBF. is formed in the fertilizer during the manufacturing. ------- 1-66 x. Toxicm A. Humans 1. Acute Toxicity The minimum lethal dose of boric acid or borates for man is not established. Intakes of up to four grams per day have been reported in an adult without incident, but single doses of 18 to 20 grams in adults have been claimed to be fatal. Intravenous doses in excess of 20 grams have been used in neutron capture therapy of brain tumors without permanent effect. The most common intoxications from boric acid result from oral intake by infants or from absorption through the skin or bladder after treat- ment for infections. The symptoms of boric acid poisoning, regardless of the route of administration, include nausea, vomiting, headache, diarrhea, erythema, hypothermy, restlessness, weariness, desquamation, renal injury, and death from circulatory collapse and shock within five days. The clinical picture of boric acid poisoning was indistinquishable from toxic epidermal necrolysis in the newborn infant. An autopsy of an infant fatally poisoned by treat- ment of oral cavity sores with boric acid solution and treatment of consequent erythema with boric acid powder revealed congestion and edema of the brain, myocardium, lungs and other organs, with fatty infiltration of the liver. Several cases of fatal poisoning due to boric acid irrigation of the bladder (118 119) after prostatectomy have been reported. ' The National Clearinghouse for Poison Control Centers reported 166 cases of boric acid poisoning, in 1972, 117 for children less than 5 years old. Infants have been accidentally poisoned in hospitals from .formulas (41) prepared with boric acid. Since no antidote exists, but equally effective treatments do, many workers feel boric acid should not be used for medical pur- poses. Some evidence exists, however, that boric acid poisoning by absorption through the skin is a serious possibility only in patients with kidney damage. Experiments conducted with rabbits showed that the biological half life of boric acid was significantly prolonged in rabbits with kidney damage. Borax is also absorbed through the skin and produces similar symptoms. Boric acid toxicity may be detected by the analysis of borates in ------- / KR/AR INC. i-67 (122) ths urine by the polyvxnyl aloohol-borate-iodine reaction since borates are rapidly excreted by the kidney in largely unchanged form. Hypoacidity in adults and decreased fecal enterokinase activity in children were observed in 288 persons drinking high boron water for pro- longed periods. Decaborane in low doses is known to have severe disruptive effects upon behavior. The symptoms include depression, catatonia, muscular fasciculations, and occasional convulsions. Little or no central nervous system damage has been reported as a result of toxicological research . . . (126) on borano fuels. Boron trifluoride is corrosive to the eyes, skin, and mucous nnEmbranes, and will cause burns on the skin similar to, but not as penetrating as, hydrogen fluoride. Boron trichloride and boron tribromide are also very corrosive. These effects are apparently due to hydrolysis of the boron trihalides to the halogen acids and not to boron. Organic derivatives of boric acid potentiate the sedative action of hypnotics. 2. Chronic Toxicity Workers engaged in the packaging of boron fertilizers complained (52) of poor appetite, nausea, and loss of weight. Aerosols and inadequate shieldinc) in the boron carbide industry may create a risk of pneumoconiosis and . (128) pneumosclorosis. Concentrations of boron compounds in the.fumss and aerosol of boric acid production were two to five times permissible levels, sulfuric acid fumes were above normal in 64% of the samples, and high temperature and humidity prevailed. Medical examinations of 291 workers revealed alterations of upper respiratory tract muoosa, arthralgia and arthropathies. The percentage of (52) gynecological diseases was rather high. Man engaged in boric acid pro- duction showed weakened sexual activity, decreased seminal volume, low sperm (129) count and motility, and increased seminal fructose. ------- I VR/AR INC. Inhalation of the dust from datolite ore (a mixture of 2CaO • B 0 • 2SiO • H20 and Ca^FeMn] . Al3B(OH)Si.O _ containing 9.5% boron), ore concentrate (15-17% boron), or silicon dioxide irritated the lungs and in- (52) hibited phagocytic activity m industrial workers. The daily ingestion of 25g of boric tartrate over a period of 20 years in one case resulted in chronic boric acid poisoning. The symptoms included cachexia, dermatitis, alopecia, hypoplastic anemia and gastric ulcer. All symptoms disappeared when the drug was withdrawn, but reappeared when therapy was resumed because of epilepsy. No medical evidence of chronic effects of boron trifluoride has been found among workmen exposed to small amounts for periods up to seven years. However, in persons subjected to boron trifluoride, disturbances of vascular permeability, enhanced tendon roflexos, joint diseases and atrophic changes in the nasal mucosa were observed.{131) B. Mammals 1. Acute Tbxicity LDrQ doses of borax and boric acid were determined in rats as shown below: LDcn of Borax & Boric Acid Sex & Strain Sprague Dawley males .Long Evans males Sprague Dawley females 5.98 0.57 4.C8 0.71 IA-n levels could rot be determined for dogs as they vomited high closes no matter how they were disguised. The animals showed no toxic effects. Acute effects of sodium pentaborate decahydrate and tetraborate decahydrate were studied by intravenous and intraperitoneal injections of rats. Acute toxicity was less with intraperitoneal injections, and injection of glucose Borax 4.50 6.08 Boron Equiv. 0.51 0.69 Boric Acid 3.45 3.16 Boron Equiv. 0.60 0.55 ------- KR/AR INC. 1-69 reduced toxic effects of pentaborate more when intraperitoneally injected than intravenously injected. Methylene blue added to a five per cent dextrose infusion 20 minutes after administration of 30 rogAg decaborane to rabbits followed by in- fusion of dilute methylene blue for 47 hours prolonged the life of the animals to over 24 or 48 hours. All untreated rabbits died within 24 hours. ^3) In monkeys, intraperitoneal injections of decaborane (6 mg per kg) resulted in death within three days. Daily injections of 1 mg per kg gave rise to an altered electroencephalogram characterized by a high frequency pattern of discharge and high voltage bursts in the hypothalamus . The LCV_ doses for inhalation exposures to pentaborane for mice and dogs were determined to be as follows: of exposure (min) U:5Q (irg/m3) Mice 1,034 342 136 50 Dogs . 734 324 92 0.5 2 5 15 o 3 The 2-minute IA-0 for monkeys was 640 rag/m . Dogs and monkeys, showed severe signs of intoxication after exposure to one half the I£r0 values, but not after one fourth or one eighth the LCL0 valiKS. No notable changes in blood cell com- ponents, BSP retention time and no gross or microscopic lesions were observed. The conditioned avoidance response was altered after 1/2 LC exposures. 2. Chronic Toxicity Effect levels in rats and dogs produced testicular degeneration in males, ,-ind cjrowth suppression and decreased food intake in both sexes. The "no effect" levels are shown below: "No l'.:f feet" Levels of Borax and Boric Acid (ppm) (35) Borax Boric Acid 4600 3000 1540 3000 ------- fAK INC. 1-70 Reproduction studies showed sterility of both species with 1170 ppm boron equivalent for both chemicals, but normal fertility, litter size, weight, and appearance occurred at 350 ppm boron equivalent. In mice boric acid produced testicular atrophy with degeneration of the seminal cells. Dogs given drinking water containing two to three mg boron per liter had decreased gastric juice secretion and decreased free and total acidity. Enterokinose activity was inhibited in intestinal juice and feces. Bats are relatively resistant to boric acid poisoning; they can survive daily doses up to 3gAg for 16 to 24 months. The males are more sensitive than the females. A 25% weight loss precedes death. Male mice given boric acid in their drinking water died within two to six months, but only 10% of the females died. Male rabbits given boric acid by gastric tube died within 36 days with up to 30% weight loss. Male rats subjected to long term dosage with boric acid had testicular atrophy and became sterile. In rats experimentally poisoned with boric acid, potassium boro- tartrate or tolboxane (2-methyl-2-propyl-l,3-propanediol p-tolylborate), urinary elimination was relatively rapid after single or repeated small doses, but was much slower with tolboxane in repeated doses than with other boron compounds. Placental passage led to a considerable diminution of vitality in young pregnant animals fed boric acid. Even though mobilization from tissues was fairly rapid, longer retention of boron occurred in some organs of chronic- ally poisoned rats.. Administration of boron to young rats during enamel formation altered the shape of teeth. Daily intragastric administration of 100 mg of calcium borate per kg to rabbits for four months gave rise to a slight increase in total serum lipids and free sulfhydryl groups in serum. Inhalation of calcium borate 3 (120-150 mg per m ) by rabbits, two hours a day for ten weeks, retarded normal weight gain, increased nitrogen compounds in the urine and increased the size of the liver. Considerable changes in the respiratory tract consisted of chronic tracheitis and bronchitis, with signs of tissue destruction over the (52) entire length of the tract. ------- / KR/AR INC. 1-71 Marked inhibition of glycolytic enzymes and an increase in methemo- qlobin was observed in erythrocytes of guinea pigs with borate toxicity. * •*••*"' Groups of rats given boric acid and thiourea via a stomach catheter exhibited more pronounced thyroid enlargement and slowing of the heart than the control group or rats receiving thiourea alone. The largest decrease in rates of radioactive iodine uptake and clearance was also observed in the former group. ' Rats were exposed to aerosols of boron oxide for as long as 24 weeks. The highest concentration used was 470 mg per m for 23 weeks. The mass median diameter of the particles was 1.9 to 2.5 microns. No deaths or other signs of intoxication were observed in rats exposed to aerosols of boron oxide at a concentration of 470 mg per m for 10 weeks. Dogs exposed to 57 mg per m exhibited increased urine volume, urine acidity and creatirine clearance. Chronic intoxication with boric acid (0.20-0.80 g per kg) affected spermatogenesis in rats, depending upon the physiological state of the testis. During the pre- puberal period, boric acid has little effect on the testis, but during puberal crisis, boric acid exerts its strongest effects. Mitotic activity in the testis is greatly lowered, sometimes resulting in complete destruction of the spermato- genie line. There is only partial sensitivity to boric acid during the adult period. Rats poisoned with sodium borohydride apparently die due to gaseous embolism subsequent to the discharge of hydrogen. ' Bradycardia, elongation of the P-Q interval by 20%, and elongation of the electric systole by 30% were some ot the cardiovascular changes observed in rabbits given 30 and 35 mg/kg doses of sodium borohydride by stomach tube. ' Decaborane (HEF-3) applications to the skin of rats gave rise to hyperercietation, aggressive behavior and central depression. Slight changes (144) in the nerve cells were demonstrated. The intraperitoneal injection of dccaborane (20 mg per kg) to rats produced a strong increase in the levels of blood in the urine within a few hours after injection. This is apparently an effect on nitrogen metabolism and not a result of kidney injury. ' Exten- sive changes in tissue amino acid levels followed borane administration in rats.' 2' ------- AR INC. 1-72 In conscious dogs, the administration of pentaborane and de- caborane produced limitations of sympathetic activity evidenced by miosis, relaxation of the nictitating membrane, bradycardia, dilation of superficial vessels, and sedation with easy arousal. Anesthetized dogs showed an initial rise in blood pressure, followed by hypotension, bradycardia and decreased response to tyramine. Pentaborane is comparatively more active in producing excitement and convulsions. Lethal injections of decaboranes in dogs produced a progressive decrease in heart force to terminal levels, but numsrous intervening sustained intervals of hypertension were observed. Progressive changes included decrease in P wave height, slow A-V nodal rhythms, occasional ectopic beats , and long periods of asystole . Intravenous perfusion of rabbits with various organoboron compounds revealed that the toxic effects of the di (parachlorobenzeneboronate) of penta- erythritol were clearly distinguishable from the others. The symptoms produced by this drug included augmentation of blood pressure with tachycardia and apnea, (61) interrupted by a sudden drop in blood pressure and bradycardia. In rats and mice the toxicity of this compound was found to be relatively lew. The sublethal dose (largest dose that can be given without causing mortality, however long the period of observation) was more than 1 g/kg intraperitoneally and 2 to 3.5 gAg orally. Rats seemed to be more sensitive than mice. Sublethal doses did not produce any signs of toxicity, but larger doses produced prolonged coma up to 48 hours. The latent period for definite onset of action is two to four days. The recovery of survivors is rapid, with no apparent sequelae. ^ ' 3- Teratogenicity Oral administration of 3.0 mg/g boric acid to mice on the first clay of preqnancy prevented 93.8% of the embryos cultured in vitro from reaching the blastocyst stage. Only 8.7% of the control embryos failed to reach the blastocyst stage. Oral doses of 0.5 or 1.0 mg/g had similar but less significant effects. Addition of .1 and .01 mg/ml boric acid to embryo cultures from un- treated mothers inhibited embryonic development to the blastocyst stage by 100% (147) and 51* respectively. v ------- M/i/< INC. 1-73 4. Allergic Reactions and Sensitization No sensitizaticn to boric acid or borax was found. In 99 patients treated for mycoses of the feet with Exanycolcgel containing 0.05% phenylrnercuric borate, five cases of eczematous irritation developed in patients (89) c who earlier had exhibited local eczema. Applications of Zyma , containing 0.06% phenylmercuric borate, under an occlusive bandage produced irritation, but on open skin, little or no response was observed. (90) Reaction to these gels is apparently due to mercury sensitivity. Skin lesions and erythema in man and mouse have been produced by thermal neutron boron-10 reactions with the skin following irradi- ation. 5. Behavioral Effects Decaborane in low doses is known to have severe disruptive effects upon behavior ' Intraperitoneal injections of one mg per kg per day of decaborane to monkeys with implanted brain electrodes produced changes in the electroencephalogram consisting of high frequency patterns of activity, and high voltage bursts in the hypothalamus. Accompanying behavior included depression, somnolence, generalized twitching and short motor seizures. Boron-deficiency in plants apparently renders them unattractive to bees. Borax application restores the attraction. Boron apparently promotes nectar secretion. 6. Carcincgenicity No evidence has been presented for the role of boron as a possible carcLnajon. Many studies on the long term selective uptake of boron by tumors have been done for possible use in neutron-capture cancer therapy. C. Nonmammalian Vertebrates Boric acid treatment produces malformations in chicken and amphibian embryos. After injection of a twenty-four-hour-old chicken yolk sac with 0.05 ml of sterile 5% boric acid solution, initial effects appeared in the three-day- old embryo. The neural tube, notochord, tail-gut and tail blastema were deformed. Pyknosis of the indifferent cell mass of the tail blastema appeared in 30-35% of the boric-acid-treated embryos. Blood vasculature was not affected in these ------- fAK INC. 1-74 rumpless chick embryos. Boric acid also produced malformations in liitfo development in chicken embryos. The results were most clearly seen in the tarsometatarsus, which was bent backwards and severly shortened. Abnormal bends in the tibiotarsus were also seen. By day 13, the effect of boric acid may be the on deswelling capacity, which affects the cartilage cells and the cartilage matrix, thus weakening the supporting body effect. Boric acid may further interfere with the process of extension of the collagen fibers, /CQ\ especially those of the sinews. Boric acid apparently exerts its teratogenic effects by conplexation of fX)lyhydroxy compounds, interfering with metabolism on the cellular level. Riboflavin content of livers of morphologically abnormal chicken embryos was sharply reduced. Addition of riboflavin or polyhydroxy compounds such as D- ribose, sorbitol, etc., to the boric acid treatment decreased teratogenic effects. Plumage color of the mother had a definite effect on progeny response to boric acid. A lower incidence of boric acid-induced abnormalities was observed in the spring. When embryos of Bufo vulgaris were treated with 0.5% boric acid for 24 hours from the two cell stage to the tail bud stage, the malformations ob- served included edema, microcephalia with rudimentary stomodaeum or sucker, approaching of the olfactory pits, short tail and a reduction or lack of external gills. The epiphysis became befurcated into a pair of vesicles of less vacuolized cells lying side by side. The forebrain showed a tendency to form a single tube with a narrow ventricle. Manorhiny, synrhiny, anophthalmia, cyclopia, and synophthalmia accompanied the suppression of forebrain development.. The bi- furcation of the epiphysis and the inhibition of sense organ development, to- getlier with the poorly developed forebrain, seem to be a result of the direct action of boric acid on the ectoderm. Vitamin C has been shown to decrease the phenylmgrcuriborate intoxic- (70) ation of Rana temperaria tadpoles. D- Invertebrates Boric acid has been demonstrated to be an effective stomach poison for several species of insects. The effect of mixtures of boric acid and sugar on the mortality of the German cockroach can be summarized as follows: ------- 1-75 Doric Acid:Sugar Mortality (%) after 72 hours 1:9 44.3 2:8 79.4 4:6 96.7 5:5 88.3 10:0 91.1 Other studies have produced similar results. ' ' Apparently the cockroaches cannot detect the presence of boric acid. Mosquito larvae differ in susceptibility to boric acid poisoning. Only 2% of the freshly hatched larvae of Anopheles quadrimaculatus reached the adult stage after treatment with 50 ppm netaboric acid. Treatment of the freshly hatched larvae of Acdes aegypti and Culex quinquefasciatus with 250 ppm boric acid allowed only 1% and 3% respectively to reach the adult stage. Elimination of various larval stages of the three species within 48 hours could be acoonplished by treatments with boric acid as follows: Larval stage Boric acid required (ppm) Freshly hatched 4,000 2nd instar 3,000 3rd instar 10,000 pupae 16,000 Insect infestation of wood and other substrates can be prevented by pretreatment with boric acid or borax. Termite attack on tie matai and radiata pine could be reduced by treatment with enough boric acid. Coptoternes spp. was more susceptible than was Nasutitermes exitiosus. Larvae of the two- toothed longhorn beetle, Ambeodontus tristis, did not survive in blocks of sap- wood kahikatea (Podocarpus dacrydioides containing 0.142% or more boric acid. 3 3 Boric acid (0.4 kg/m of wood) and borax (0.55 kg/m of wood) were lethal to egq-larvae of lly.lotrupes bajulus after 12 weeks. The lethal doses required for _j ^ 3 elimination of Uic infestation within six months were 0.3 kg/m and 0.35 kg/m respectively. Older larvae of H. bajulus and Anobium punctcvtum were only slowly affected. Powder post beetle attack was prevented by treatment of the ------- 1-76 ZOO ISO '•-... SUGAR BEET UJ O oc. LU Q. 5 10 15 20 25 PPM BORON IN SOIL SOLUTION Effect of Boron concentration ------- 1-77 rubberwood (Hevea brasiliensis) with boron salts. ' Treatrtent of wool with boric acid effectively controlled black carpet beetle larvae. ' Traps baited with cottonseed hydrolysate containing borax reduced infestation of navel oranges by fruit flies (Anastrepha ludens) by 68%, and in mangoes, by 98%. The toxicity of organoboron compounds makes them useful as insecticides. Isobomyl thiocyanoacetate (IBTA) had an LD5Q of 27.3 micrograms per insect against domestic houseflies. Aerosol borttos containing IBTA had a KT-. (knock- down time) of six minutes. The effectiveness of IBTA was greatly decreased in concentrations below two per cent. Boronyl acetate from the volatile oils of conifers was the most toxic of the components of the oil to the larvae of Tribolium destructor.(165^ Boric acid and other boron compounds have been demonstrated to be effective chemosterilants of the housefly, Musca domestica,(166' 16') and the oottcn boll weevil. E. Plants Although boron is a nutritional requirement for most plants, too much boron is toxic. The dual effects of boron are illustrated in Figure 9, ^•L&B' 3::>' The amount of boron in saturation-extract concentrations of the soil is plotted against the plant weight expressed as a percentage of the average weight of the plant grown in soil containing trace boron. Plants are classified as sensitive, semitolerant or tolerant to boron in soil extracts in two ways. Table 10 lists crop species in groupings based on the levels of boron in micrograms per ml of soil extract which produce toxic effects. ' The most sensitive plants are listed at the top of each column. Plants arc also classified into three categories based on a relative tolerance index. The i.ndex is 100 tiircs the ratio of the averaged weight of plants grown in 5, 10 and 15 ppm boron to the largest weight of plants grown in either trace or 1 ppm boron Table 11 summarizes this data. The toxic symptoms of boron include stunted growth, malformations of loaves, browning and yellowing, chlorosis and necrosis. Pollen germination and ------- \R INC. 1-78 !U. 'l\)X.lt' lentil OuhifiMtralichB uf Etal uratidtt Kxtracts for Sensitive, Semitolerant Crop Species* (35) Saturation-Extract Boron, ygrams of B/inl 0.5-1.0 Sensitive Citrus Avocado Aprioot Peach Cherry Persimmon Fig Grape Apple Pear Plum Navy bean Jerusalem artichoke WaJ-nut 1.0-5.0 Semitolerant Lima bean Sweet potato Bell pepper Oat Milo Com Wheat Barley Olive Field pea Radish Tomato Cotton Potato 5.0-10.0 Tolerant Carrot Lettuce Cabbage Turnip Onion Broad bean Alfalfa Garden beet Mangel Sugar beet Palm Asparagus ""Listed in each category according to susceptibility to boron injury (viz., citrus is more sensitive than walnut, lima bean more than potato, etc.). ------- INC, 1-79 PLANT Table 11. Plant Growth as Affected by Boron (35) Boron Cone. Lowest Cone. For Best Growth For Injury (ppm) (ppm) Relative Tolerance Index SENSITIVE PLANTS Blackberry (Rubus sp.) Trace Lemon (Citrus limonia osbeck) Trace Elm (Cimus americana. L.) 1 Cherry (Prunus arium L.) 1 Peach (Prunus. pergica (L) Batsch) 1 Persimmon (Diospyrps kaki L.f.) 1 Fig (Ficus carica L.) 1 Strawberry (Fraqaria sp.) 1 Lupine (Lupinus hurtweqi Lindl.) 1 Grape (Vitis roxiifera L.) l Violet (Viola odorata L.) Trace I'ansy (Viola tricolor L.) Trace Kidney bean (Phaseolus vulgaris L.) 1 Cowpea (Vigna sinensis (Torner) Savl) Trace Jerusalem artichoke (Helianthus tuberosus L) 1 Larkspur (Delphinium sp.) 1 Zinnia (Zinnia elegans Jacq.) Trace 1 1 1 5 5 1 5 5 5 5 5 5 1 1 5 1 9 20 24 30 34 43 45 Boron Deficiency Symptom; With Trace Boron* S None S S 2 S S None M S None None None D None S None SEMI-TOLERANT PLANTS Barley (llordeurn yulcjare L.) Pea (Pisum satlvum L.I .Lima tean~(jPhaseoTus tunatus L.) Sweet Potato (Ipoinoca batatas (L) Lam.) Onion (A.1 .lium cepa L.) Carrot (Daucus carota L.) Red pepper (Capsicum frutescens L.) Kentucky bluegrass (Poa pratensis L.) Com (2ea mays L.) Potato (Solanum tuberosum L.) Cabbage (Brassica oleracea var. capitata L.) Milo (Sorghum vulgare Pers.) Calendula (Calendula officinalis L.) Trace 1 Trace Trace Trace Trace Trace 5 1 1 1 Trace Trace 5 5 1 5 1 10 1 5 1 10 5 51 55 57 63 68 70 71 86 53 78 78 (8) 80 D None S S None None None None None S None M None ------- 1-80 Table 11 (Can't) Plant Growth as Affected by Boron Boron Cone. Lowest Cone. Relative For Best Growth For Injury Tolerance PLANT (ppm) (ppm) Index SEME-TOLERANT PLANTS (Con't) Radish (Raphanus sativus L. ) 1 10 60 Oats (Avena sativa L. ) Celery (Apium graveolens L. ) Mustard (Brassica sp.) Parsley (Petroselinum crispum (Mill . ) Nym. ) Alfalfa (Medicago sativa L.) Lettuce (Lactucca sativa L.) Tobacco (Nicotiana tonientosa Ruiz and Pav. ) Vetch (Vicia atropurpurea Desf.) 'lomato (Lyoopcrsicon esculentum Mill.) California Poppy (Eschscholtzia califoimca Cham.) Turnip (Brassica rapa L.) Coimon beet (Beta vulgaris L.) Leaf beet (Beta vulgaris var. cicla L.) Muskmelon (Cucumis melo L.) Sweet clover (melilotus indica(L.)All.) Sweet pea (Lathyrus odoratus L. ) Sugar beet (Beta vulgaris var. crassa Alef .) Oxalis (Oxalis bowiei Herb.) Cotton (Cossypium hirsutum L.) Artichoke (Cynara scolymus L.) 5 15 1 5 10 5 15 5 10 5 TOLERANT 5 5 5 5 5 10 5 10 10 5 5 25 10 15 15 1 10 5 5 5 PLANTS 25 15 25 5 10 5 15 None 10 5 86 89 94 95 106 96 96 98 99 99 115 112 110 107 . 110 113 121 121 130 123 (Asparagus officinalis L.) 51 25 *S .= presence of leaf or other morphological abnormalities. M = tinn of flowering or ripening substantially affected. D = trace-boron plants more severly attacked by mildew. W = severe wilting. 217 Boron Deficiency Symptoms With Trace Boron* S None S None None None None None None None None None W D None S None S S S ------- 1-81 and pollen tube growth may be inhabited. Symptoms of boron toxicity in various plant species are summarized in Table 12. Necrotic leaves in sugarcane averaged 657.7 ppm boron, while green leaves averaged 55.7 ppm. In China asters, if analysis of old leaf tissue reveals a boron content of 750 ppm (dry weight basis), boron is the probable cause of injury. If the tissue of a newly matured leaf of Mathipln incana contains 200 ppm boron or more (dry weight basis), the boron injury will probably be severe enough at the time of harvest to make the i n (170> crop unsalable. In turf grass species, the species with rapid boron accumulation showed leaf tip injury first. The practice of mowing removed the high boron concentration in the leaf tips. The boron concentration of small areas of leaves of rough lemon may be 100 tines higher than that in the petioles, and the boron toxicity symptoms are reflected in this distribution. ' The addition of lime to soils containing high concentrations of boron reduces the degree of injury by boron. ' ' 2-Choroethanol apparently increases the boron resistance of wheat seedlings subject to boron toxicity. ' Phenylboric acid (PhB) produces toxic effects at lower levels than boric acid. Addition of 300 mg/1 PhB to tomato, Oospora lactis, produced conspicuous abnormalities of cell and leaf form not observed with 300-500 mg/1 boric acid.' ' Severe flower malformations (open pistils, tripistilly, and pistilloidy) in L'isuni plants resulted from a single PhB treatment. Lanceolate leaf shape was induced in Solanum lycopersicuns by PhB. The foliage of Stellaria media seedlings was altered by a 2x10 M solution of PhB. ' PhB stimulates the lanceolate gene in the tomato. In addition to a change in leaf form, increases in the activities of tyrosinase, laccase, peroxidase, and catalasc occur. It is suggested that the mutant alleles of the lanceolate gene, as well as PhB, produce increased oxidative enzyme activity, which results in an alteration in leaf form.'-'-'"' Diarylboronic acids were toxic to wheat roots at 10 M; 4x10 ' M benzeneboronic acid hampered pollen germination and pollen tube growth. ' ------- Table 12. Synptoms of Borcn loxicity species cucimber squash nuskrrelon corn carnation (Planthus caryophyllus) Mathiola incana peach citrus Chrysanthemum morifolium groundnut horsebean peach sugar beet sunflower Pinus radiata hydro- ponic culture Boron Levels 6 ppm 12 ppn ' 12 per, 16 180g_or 270g to soil 2 . 5 ppm 10 ppm Synptoms Reference 50% decrease in top (87) 50% decrease in top (87) 50% decrease in top (87) 50% decrease in top (87) Ibnecrosis of leaf tips (34) "considerable injury" (213) Sloughing off of necrotic ground (214) parenchyma cells along abaxial leaf midrib Chlorotic leaves at top and base (215) of affected shoots. Necrosis at tip and margins more pronounced in older leaves Marginal and interveinal yellowing; (216) necrosis Severe yellowing of leaves, chlorosis (221) Browning; necrosis chloroplasts dis- (217) integrate, thykaloids of matrix first, then grana and outer menbrane Delayed and scant blossoming; mal- (218) formed fruits Ladle-shaped leaves, decreased yield; (180;74) increased transpiration Morphological changes (180) Decreased amount and concentration (219) of NgK, P, Ca, Mg, Cu, Zn CO ------- Species Setaria sphacelata tall wheat Cflgropyron elcngatum) maize citrus fruits Citrus sinesis Citrus reticulata berseem oats cabbage Kalai red bean vable 12. Synptoms of Boron Tbxicity (Con't) Boron Levels Synptcms 50 mg/1 3>38 pprr. B, no Ca 0.47-5 ppr< in soil around roots > Ippm-sand > 2ppn—loarn Inhibition of pollen germination and pollen tube growth 50% decrement in growth Iteduced germination and pollen tube growth Less chlorophyll; higher water con- tent; thicker, smaller leaves tree collapse water absorption affected 4.8 ppra > 11 ppm 100 Ib/2xl06 Ibs soil > 500g/10 acres reduced yield Reference (174) (205) (206) (207) (208) (192) (209) (209) (210) (211) CO CO ------- KR/AR INC. . i-84 Morphological changes in the sunflower characteristic of maternal plants briefly deprived of boron persisted throughout one gsneration, and even in the third generation, the changes were retained in isolated instances. ^180' F. Microorganisms The use of boric acid as a fungicide and an antiseptic is discussed under "Therapeutic Uses." A genetic transformation of Strain 1029 of Actinomyces indigocolor which was previously grown and adapted to a low boron medium was effected with the aid of DNA from A. indigocolor, Strain 1100, which was adapted to a medium • • ~ *T~ 0.81) containing an excess of boron. After a 10 minute germicidal ultraviolet irradiation, the surviving spores of an actinomycete (Streptornyces spp.) were highly resistant to phenyl- msrcuric borate, a disinfectant. Spores irradiated for two minutes were not so resistant. G. Rasults of Personal Contacts with Medical Personnel A total of 74 toxicologists and medical examiners in various parts of the United States vere contacted by letter or telephone under this program. It was inquired of these contacts whether they, in their professional experi- ence, had encountered a case of human poisoning by boron compounds. Of the 31 responses, there were nine reports of poisonings by boron compounds. Of these, five cases proved fatal. Most of the cases reported for boron involved the misuse of boron compounds (borax or boric acid solutions, boric acid powder) in hospitals. Of the five fatal poisonings, four were of this type: ( 3 arose fixan accidental substitution of boric acid solution for water in infant formula 1 arose from accidental use of boric acid as a diapering powder The other fatality apparently arose from the spraying of borax onto forest fires. Although details are not known it is surmised that the victim was inundated when a large amount of borax solution was dumped from a tank. ------- f TT i-85 [\R INC, One reply mentioned that boron (or its oonpounds) has soros repute as an aphrodisiac, and that the respondent had noted a urine and gastric . sample of unusually high boron content. The condition of the patient was not known. ------- \R INC. XI. CURRENT REGULATIONS AND EFFECTS LEVELS A. Toxicity Levels LD50 (dosage at which 1/2 test animals die) - from tests on rats (222) by oral administration: Material mg/kg of body weight Borax 6050 Boric acid . 5140 Irrigation waters - limit of 1 ppm boron (no official limitation) Proposed criteria according to type of crop to be irrigated: Crop Species Critical boron concentration, ppm Sensitive 0.3 - 1.0 Semi-tolerant 1.0 - 2.0 Tolerant 2.0-4.0 Sensitive plants: blackberry, lemon, elm, cherry, peach, persimmon, fig, strawberry, lupine, grape, violet, pansy, kidney bean, cowpea, Jerusalem artichoke, larkspur, zinnia. The presence of boron in great enough concentration to cause crop damage in some potential irrigation water in parts of Western United States has prompted proposals for criteria for the boron content of irrigation water. No (9) official standard has been set yet. (223) B. Transportation and Handling Regulations The only boron compounds covered in this survey are those which are included in "Commodity List of Explosives and Other Dangerous Articles". They are boron trichloride, boron trifluoride, decaborane and pentaborane. Boron trichloride is classified by the Interstate Commerce Conmission as a corrosive liquid, requiring a white label. The maximum quantity allowed in containers by rail express is 1 liter. International Air Transport Associ- ation (IATA) regulations limit its transport to 1 liter carried in cargo planes only. ------- 1-87 rAR [N(l Boron trifluoride is a nonflammable gas, requiring a green label. It is restricted to 140 kg in one outside container by rail express. IATA regulations permit the transport of up to 140 kg in cargo planes only. Decaborane is classified as a flammable solid requiring a yellow label. Rail transport is limited to 12 kg in one outside container. IATA regulations permit cargo planes only to carry up to 12 kg of decaborane. Pentaborane is a flamnable liquid, requiring a red label. It is not accepted for rail express. IATA regulations prohibit its transport in both passenger and cargo planes. C. Foreign Regulations In the U.S.S.R the recommended maximum permissible concentration 3 (224) of calcium borate dust in the air of working locations is 4-6 mg/m of air. ------- 1-88 fAK INC. XII. STANDARDS 3 (225) Boron oxide - TLV - 10 mg/m . This value was reoaranended in view of the very low toxicity of test animals to boron oxide aerosols. 3 (225) Boron trifluoride - TLV - 1 ppm*(approximately 3 mg/n ). ' Boron tribromide - TLV - 1 ppm*(approximately 10 mg/m ).^ ' *parts per million by volume ------- 1-89 XIII. SUMMARY AND CONCLUSIONS A. Summary Boron is a ubiquitous element, found in 10 to 30 ppms in soils, about 0.1 ppm in surface waters, and 4.5 ppm in sea water. In spite of this, the domestic sources of boron raw materials are concentrated in the desert areas of California, and consequently the processing plants for these raw materials and those for production of bulk boron chemicals are located within a small region. The major raw material in this case is borax, which is the keystone of the boron industry. A consequence of this situation is that con- tamination of the environment from natural sources of boron materials is found within a relatively limited area. Boron enters the environment at a rate of approximately 32,000 metric tons per year for the United States. Most of this ends up in the waters. About one-half of the total amount enters the water directly from laundry pro- ducts and sewage. Boron compounds are absorbed by the intestine, mucous membranes and skin. Excretion is mainly via the urine, but complete excretion is slow and boron may accumulate. Inorganic borates are quite toxic, apparently complexing hydroxy compounds and interfering with protein synthesis. Organoborate compounds exert physiological effects on the peripheral and central nervous system, acting as spasmolytics, sedatives and convulsants, depending upon the structure. Boranes produce toxic effects by creating embolisms of hydrogen gas as they react with tissue. No boron carcinogenic!ty has been reported. Erythema and swelling may develop in individuals sensitive to boron. Boric acid is a potent teratogen when applied directly to the embryo. Boron compounds are selectively accumu- lated by some types of tumors and boron-10 compounds are used as neutron capture targets for tumor localization and treatment. Boron is a growth requirement for plants and not for animals, but fax) much boron is phytotoxic. Plant species vary greatly in their sensitivity to boron toxicity. Boron compounds have been widely used as fertilizers, in- ------- 1-90 secticides, fungicides, and bacteriocides. The long range effects of boron oorrpounds on fish and birds and other marine organisms have not been investigated. Medical and household use of boric acid solutions as antiseptics has led to numerous accidental poisonings through ingestion or absorption through the skin, particularly in infants. Boric acid and borax are used as insect control compounds in wood preservation. Boric acid is also used to eradicate cockroaches. D. Conclusions The following conclusions are based on the material presented in this report on environmental effects of boron and its compounds: 1. Environmental contamination of the air with boron compounds does not appear to pose an environmental problem. Hazardous atmospheric con- ditions stemming from high concentrations of boron or its compounds is entirely localized. 2. Future build-up of boron in ground waters could cause detrimental effects to aquatic and other species of plants and animals. This is presently the case for areas where natural boron deposits are found. Plant toxicity effects could become generalized if boron-containing cleansing agents become more widely used in this country. 3. 'Che acute toxicity of humans to boric acid has led to an in- ordinate number of poisonings which could probably have been prevented by minimal use of warning labels or substitution. C. Recommendations The following recommendations are based on the conclusions pre- sented in Section XIII C above: (1) Boron increases in U.S. waters should be closely studied with regard to effects on aquatic species should the use in this country of boron- containing cleansing agents increase significantly. Any detrimental effects should be noted first in Europe, where such usage of boron compounds is already intensive. ------- 1-91 'Mi/Alt I ML ' (2) Use of boric acid (and, perhaps, other boron-containing conpounds) as externally applied antiseptics (or similar uses) should be discouraged because of its toxicity. Further study should be made to ascertain proper regulation in this case. ------- 1-92 fAH INC, References (1) Stanford Research Institute. U.S.A. Chemical Information Ser- vices. 1974 Directory of Chemical Products, Boron Chpt. Menlo Park, California, 1974. (2) Blue, Thomas A. Boron Minerals and Chemicals, Chemical Economics Handbook. Stanford Research Institute. Menlo Park, California, 1972. (3) General Technologies Corp. Development Document for Proposed Effluent Limitation Guidelines, United States Environmental Pro- tection Agency, 68-01-1513, December, 1973. (4) Minerals Yearbook 1972, Boron Chpt, Bureau of Mines, U.S. Depart- ment of the Interior. Washington, D.C., 1974. 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