Silicon

Excerpt from ERG Guide 170 [Metals (Powders, Dusts, Shavings, Borings, Turnings, or Cuttings, etc.)]:

Use special powder, dry sand. NO hydrous agents.

Fresh air, rest.

Rinse skin with plenty of water or shower.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth.

· CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper not available or no answer, refer to appropriate telephone number listed on the inside back cover.

· ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area.

Excerpt from NIOSH Pocket Guide for Silicon:

General First Aid:

(General first aid procedures)

This chemical is a combustible solid. Use dry chemical, carbon dioxide, or foam extinguishers ... If material or contaminated runoff enters waterways, notify downstream users of potentially contaminated waters. Notify local health and fire officials and pollution control agencies. From a secure, explosion-proof location, use water spray to cool exposed containers. If cooling streams are ineffective (venting sound increases in volume and pitch, tank discolors or shows any signs of deforming), withdraw immediately to a secure position ... The only respirators recommended for fire fighting are self-contained breathing apparatuses that have full facepieces and are operated in a pressure-demand or other positive-pressure mode.

If material on fire or involved in fire: Solid streams of water may spread fire. Use water in flooding quantities as fog. Use dry chemical, graphite, or dry earth. /Silicon powder, amorphous/

Water may not be effective in extinguishing the flames. /Silicon powder, amorphous/

Spill handling: evacuate persons not wearing protective equipment from area of spill or leak until clean-up is complete. Remove all ignition sources. Collect powdered material in the most convenient and safe manner and deposit in sealed containers. Ventilate area after clean-up is complete. It may be necessary to contain and dispose of this chemical as a hazardous waste. If material or contaminated runoff enters waterways, notify downstream users of potentially contaminated waters. Contact your Department of Environmental Protection or your regional office of the federal EPA for specific recommendations.

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.

The substance can be absorbed into the body by inhalation.

inhalation, ingestion, skin and/or eye contact

Cough.

Redness. Roughness.

Redness.

irritation eyes, skin, upper respiratory system; cough

Silicon is not found free in nature, but occurs chiefly as the oxide, and as silicates. Sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal are some of the oxide forms. Granite, hornblende, asbestos, feldspar, clay mica, etc. are but a few of the numerous silicate minerals. Twenty-four radioactive isotopes are recognized. Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant element.

Three naturally occurring isotopes: 28 (92.18%); 29 (4.71%); 30 (3.12%) ... Found as silica (quartz, sand, sandstone) or as silicate (feldspar, orthoclase, kaolinite, anorthite).

/SIGNS AND SYMPTOMS/ Causes irritation of the eyes, skin, and upper respiratory system; cough. Silicon dust does not produce significant organic disease or toxic effect when exposures are kept under reasonable control. Unpleasant deposits may be caused in eyes, ears, and nasal passages, and injury to the skin and mucous membranes may be cause by the dust itself or by cleansing procedures used for its removal.

/CASE REPORTS/ ... Increased renal silicon (200 ppm dry weight; normal = 14-23 ppm) /was found/ in an adult male bricklayer who presented with proteinuria and hypertension, but who had a normal chest roentgenogram. Moderate thickening of the glomerular basement membrane was noted on transmission electron microscopy.

/ALTERNATIVE and IN VITRO TESTS/ ...The in vitro cytotoxicity of mesoporous silicon (PSi) microparticles on the Caco-2 cells /is described/ as a function of particle size fractions (1.2-75 microm), particle concentration (0.2-4 mg/mL) and incubation times (3, 11 and 24 hr). The particle size (smaller PSi particles showed higher cytotoxicity) and the surface chemistry treatment of the PSi microparticles were considered to be the key factors regarding the toxicity aspects. These effects were significant after the 11 and 24 hr exposure times, and were explained by cell-particle interactions involving mitochondrial disruption resulting from ATP depletion and reactive oxygen species production induced by the PSi surface. These events further induced an increase in cell apoptosis and consequent cell damage and cell death in a dose-dependent manner and as a function of the PSi particle size. These effects were, however, less pronounced with thermally oxidized PSi particles. Under the experimental conditions tested and at particle sizes >25 um, the non-toxic threshold concentration for thermally hydrocarbonized and carbonized PSi particles was <2 mg/mL, and for thermally oxidized PSi microparticles was <4 mg/mL.

/OTHER TOXICITY INFORMATION/ ... /The authors/ examined inorganic particles in the pulmonary hilar lymph nodes affected by idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP) to investigate whether inhaled elements are involved in the etiology, and whether there is an increasing risk of developing IPF/UIP. Twenty-three IPF/UIP cases and 23 controls without IPF/UIP were investigated. Pulmonary hilar lymph nodes constituted the study material. The elemental analysis was performed using scanning electron microscopy with an energy dispersive X-ray spectroscope, and ... particles /were analyzes/ quantitatively and qualitatively. The results showed that the cases contained silicon and aluminum as compared with the control in lymph nodes, and these deposits were statistically significantly associated with an increased risk of IPF/UIP (adjusted odds were 2.99, 95% CI: 1.29-6.85 and 57.84, 95% CI: 1.45-2306.19, respectively)...

/LABORATORY ANIMALS: Acute Exposure/ ... Slight pulmonary epithelial lesions /were found/ in rabbits after intratracheal instillation of silicon dust at 25 mg.

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ When guinea pigs and albino rats received an ip injection of 0.1 to 0.2 g of 99.85% elemental silicon and evaluated at up to 60 days after treatment, only minor local trauma and foreign-body reaction developed; parenterally, elemental silicon was considered biologically inert.

/GENOTOXICITY/ The genotoxicity of silicon (Si) is investigated by soaking crystalline Si in a complete culture medium for 60 days and conducting micronuclei tests (MNTs) utilizing hamster ovary (CHO) cells and its Ku80 deficient CHO mutant (xrs5) cells (DNA double-strand breaks repair deficiency). The intracellular concentrations of reactive oxygen/nitrogen species (ROS/RNS) on Si are determined to elucidate the relationship between ROS/RNS and Si-induced genotoxicity by using CHO cells. The cells are treated with ROS scavenger (dimethyl sulfoxide) and MNT are performed. The results indicate that the intracellular concentration of ROS and nitrogen oxide (NO) on Si is higher than those on the control group by about 38% and 12%. ROS/RNS include superoxide (O(2)*(-)) anion, NO, and peroxynitrite (ONOO(-)) which can injure chromosomes and induce high cellular DNA double-strand breaks (DSBs).

/ALTERNATIVE and IN VITRO TESTS/ ... The objective of this study was to compare biological responses of silicon nanoparticles (SNs, 3 nm diameter) with silicon microparticles (SMs, approximately 100-3000 nm diameter) in cultured murine macrophages (RAW 264.7) using standard protocols for assessing cytotoxicity/cell viability and inflammatory responses developed for micron-sized particles. SNs and SMs were exposed to macrophages with and without addition of endotoxin lipopolysaccharide (LPS), a positive inducer of tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), and nitric oxide (NO). Cytotoxicity was assayed using the dye exclusion and MTT assays. Cell supernatants were assayed for production TNF-alpha, IL-6 and NO. SNs at concentrations < or = 20 ug/mL exhibited no cytotoxicity or inflammatory responses; however, SNs and SMs >20 and 200 ug/mL, respectively, increased cytotoxicity compared with controls. SMs induced concentration-related increases in TNF-alpha and IL-6 production; in contrast, the production of these cytokines was shown to decrease with increasing concentrations of SNs. NO production was not induced by SNs or SMs alone. Fluorescence microscopy demonstrated that SNs were associated with the macrophages, either internalized or attached to cell membranes...

/ALTERNATIVE and IN VITRO TESTS/ Cytotoxicity test with silicon (fine gray powder with particle size of 0.1 - 2.0 um). Alveolar macrophages washed from lungs of New Zealand white rabbits were incubated with silicon powder at 37 °C for 20 hr on a rocker platform. 9 concentrations between 30 and 1000 ug/mL in suspension were tested; cell viability determined after staining with trypan blue (supravital stain). 16 observations per dose. Negative and positive controls. Results: silicon powder had an LC50 of 199 ug/mL (95% confidence limits 116-339 mg/mL). Apparently no water soluble component was responsible for cytotoxicity. Classified by USEPA as extremely cytotoxic.

According to the 2006 TSCA Inventory Update Report, the number of persons reasonably likely to be exposed in the industrial manufacturing, processing, and use workers of silicon is 1,000 or greater; the data may be greatly underestimated(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 693,583 workers (28,164 of these were female) were potentially exposed to silicon in the US(1).

Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR as necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Irritating materials/

Basic Treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Encourage patient to take deep breaths. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . /Irritating materials/

Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Early intubation at the first sign of upper airway obstruction may be necessary. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... .Treat seizures with diazepam or lorazepam ... Use proparacaine hydrochloride to assist eye irrigation ... . /Irritating materials/

LC50; Rabbit (alveolar macrophages in culture); Concentration: 199 ug/mL for 20 hr (95% confidence limits 116-339 mg/mL); Conditions: temp 37 °C

LD50 Rat oral 3160 mg/kg