Toxicity Report

A Review of General Acute Toxicity Studies of Boron-Containing Insulation Products Prepared for Nu-Wool® Company, Inc.

Executive Summary

Intertox, Inc. has extensive experience reviewing the general use and toxicity of boron-based products, and in particular sodium polyborate. A general review of boron-based compounds indicates that these compounds occur naturally in low concentrations in air, water, and soil and are of generally low toxicity. We review here six acute animal toxicity studies in which a boron-containing cellulose insulation (BCI) product,1 essentially identical to Nu-Wool® Company, Inc.'s Nu-Wool® and Nu-Wool® WALLSEAL® Insulation products,2 was tested. The acute toxicity studies reviewed include those examining adverse health effects associated with contact with the product on the skin and eyes and through inhalation and ingestion. These studies appear to have been performed according to acceptable experimental protocols.

Four of the six studies reviewed indicate no observed adverse health effects from exposure of the test animals to the BCI, hence to Nu-Wool® and Nu-Wool® WALLSEAL®. A fifth study indicated temporary and minimal eye irritation when the product was placed under the test animals eyelids. The sixth study, an oral toxicity study, successfully established the benchmark toxicity measure LD50 for the product, by only treating animals with the pure active ingredient of Nu-Wool® and Nu-Wool® WALLSEAL®, sodium polyborate. The LD50 for sodium polyborate was estimated to be 3,339 mg/kg3 while that of Nu-Wool® and Nu-Wool® WALLSEAL® would be 26,710 mg/kg3, indicating that the products, as formulated, have lower toxicity than products such as aspirin. Further, test animal ingestion of the BCI in the range of this amount was regarded by those conducting the study as impractical because of the bulkiness and low density of the product. Based on these reviews and assuming foreseeable circumstances of exposure during product application or occupation of a structure treated with Nu-Wool® or Nu-Wool® WALLSEAL®, we do not expect the product to cause adverse health impacts beyond those that are mild and temporary.

Notes:

1 Boron-containing material added to cellulose insulation contains 100% sodium polyborate. Animal tests cited herein were conducted using a cellulose insulation product that contained similar concentrations of sodium polyborate and shredded newspaper.

2 The chemical load factors for Nu-Wool® and Nu-Wool® WALLSEAL® are approximately 12.5% by weight. Based on information provided by Nu-Wool®, the two products having similar formulation of Boron-10® (8.9%) and boric acid (3.6%).

3 Since Nu-Wool® and Nu-Wool® WALLSEAL® contain at most 12.5% of the active ingredient, a comparison between the toxicity of the active ingredient and the material as a whole can be made by dividing the LD50 for the sodium polyborate by the fraction of sodium polyborate in the insulation (0.125). Hence 3,339 mg/kg ÷ 0.125 = 26,710 mg/kg. Note that we assume that the other ingredients in the insulation (i.e. cellulose) are not of toxicological significance if ingested.