ALUMINUM AND COMPOUNDS

CAS Registry Number: 7429-90-5

Molecular Formula: Al

Description

Aluminum is a malleable, ductile, silver-white metal, with a somewhat bluish tint and can appear as a crystalline solid. It can be polished and will retain the polish in dry air, however, in moist air, an oxide film forms (about 50 Angstroms thick) which protects the metal from corrosion. Aluminum is soluble in alkalis, hydrochloric acid, and sulfuric acid. It is insoluble in water, concentrated nitric acid, and hot acetic acid. Aluminum is a good conductor of heat and electricity and can have a high tensile strength. The powder form is combustible (HSDB, 1993). Aluminum phosphide must be protected from moist air since it reacts readily to produce phosphine which is highly toxic. Aluminum phosphide treated with water and acid produces phosphine in quantitative yields (Merck, 1989). (For information on exposure and health effects on phosphine, see the fact sheet on phosphine.)

Physical Properties of Aluminum

Atomic Number13
Atomic Weight26.98
Valence3
Boiling Point2327 oC
Melting Point660 oC
Density2.702
Vapor Pressure1 mm at 1284 oC

(HSDB, 1993; Merck, 1989)

Examples of Aluminum Compounds

Aluminum aceglutamide, Aluminum fluoride, Aluminum azide, Aluminum hydride, Aluminum borohydride, Aluminum hydroxide, Aluminum bromide, Aluminum nitrate, Aluminum carbide, Aluminum oxide, Aluminum chloride, Aluminum phosphide, Aluminum clofibrate, Aluminum silicate, Aluminum dextran, Aluminum flufenamate

SOURCES AND EMISSIONS

A. Sources

Aluminum is produced in bars, leaf, powder, sheets, or wire. Aluminum is used in building and construction; in corrosion-resistant chemical equipment (desalination plants); in electrical industries (power transmission lines); for photoengraving plates; in permanent magnets; for machinery and accessory equipment; in tubes for consumer products; in paints and coatings; as rocket fuel; in fireworks; in packaging; and, as flakes for insulation of liquid fuels (Sax, 1987). Other uses are in printing inks and the manufacture of cans and containers. The aluminum mineral bentonite is used in water purification, sugar refining, and in the brewing of alcohol and paper industries (HSDB, 1993). Aluminum sulfate is also manufactured in California (SRI, 1993). The primary stationary sources that have reported emissions of aluminum compounds in California are crushed and broken stone mining, metal working machinery, and national security systems (ARB, 1997b).

In California, aluminum phosphide and aluminum tris(O-ethyl phosphate) are registered pesticides. Aluminum phosphide is registered as a insecticide. It is used to control stored product insects and is registered for use for fumigating raw agricultural commodities, animal feed ingredients, processed foods (sugar, flour, etc.), tobacco, wood, paper, leather, human and animal hair, feathers, etc. It is also registered for vertebrate control (rats, mice, squirrels, gophers etc.) in and around mills, food processing plants, warehouses and silos, and in rail cars, ships, and shipping containers (DPR, 1996). Aluminum tris(O-ethyl phosphate) (Fosetyl-Al) is registered as a fungicide. It is used for the control and prevention of plant diseases on citrus, avocado, almonds and other nut crops. It may also be applied to small fruit crops (blackberry, boysenberry), and to a variety of leafy vegetable (spinach, lettuce, collard greens) and to cole crops (cabbage, broccoli) (DPR, 1996).

The licensing and regulation of pesticides for sale and use in California are the responsibility of the Department of Pesticide Regulation (DPR). Information presented in this fact sheet regarding the permitted pesticidal uses of aluminum phosphide, or aluminum tris(O-ethyl phosphate) has been collected from pesticide labels registered for use in California and from DPR's pesticide databases. This information reflects pesticide use and permitted uses in California as of October 15, 1996. For further information regarding the pesticidal uses of these compounds, please contact the Pesticide Registration Branch of DPR (DPR, 1996).

Aluminum sulfate was registered for use as a pesticide; however as of January 17, 1990, it is no longer registered for pesticidal use in California (DPR, 1997).

B. Emissions

The total emissions of aluminum compounds from stationary sources in California are estimated to be at least 4,000 pounds per year, based on data reported under the Air Toxics "Hot Spots" Program (AB 2588) (ARB, 1997b).

C. Natural Occurrence

Aluminum is one of the most abundant metals in the earth's crust. It occurs 8.8 percent by weight primarily in combination with silica as aluminum silicate and also with oxygen and fluorine. Important natural sources of aluminum are bauxite, cryolite, alum, corundum and the kaolin minerals. Some acid soils contain sufficient aluminum to kill certain plants (HSDB, 1993).

AMBIENT CONCENTRATIONS

Aluminum and its species are routinely monitored by the statewide Air Resources Board air toxics network. The network's mean concentration of aluminum (including its species) from January 1996 through December 1996 is estimated to be 1.4 micrograms per cubic meter (ARB, 1997c).

INDOOR SOURCES AND CONCENTRATIONS

In a field study conducted in southern California, investigators collected particles (PM10) inside 178 homes and analyzed the particle samples for selected elements, including aluminum. Two consecutive 12-hour samples were collected inside and immediately outside each home. Average indoor aluminum concentrations were 2,300 nanograms per cubic meter (ng/m3) in the daytime and 1,200 ng/m3 in the nighttime. Corresponding average outdoor concentrations were similar; 2,300 ng/m3 in the daytime and 1,500 ng/m3 in the nighttime. Indoor concentrations ranged from approximately 240 to 15,000 ng/m3 (Pellizzari et al., 1992).

ATMOSPHERIC PERSISTENCE

Aluminum compounds are expected to be particle-associated in the atmosphere, and hence subject to wet and dry deposition. The average half-life for particles and particle-associated chemicals in the troposphere is estimated to be approximately 3.5 - 10 days (Balkanski et al., 1993).

AB 2588 RISK ASSESSMENT INFORMATION

Although aluminum compounds are reported as being emitted in California from stationary sources, no health values (cancer or non-cancer) are listed in the California Air Pollution Control Officers Association Air Toxics "Hot Spots" Program Revised 1992 Risk Assessment Guidelines for use in risk assessments (CAPCOA, 1993).

HEALTH EFFECTS

Probable routes of human exposure to aluminum are ingestion and inhalation.

Non-Cancer: Aluminum dusts are mildly irritating to the eye and respiratory tract. Inhalation of the dust can lead to alveolar proteinosis. In some studies, prolonged exposure of workers to high levels of very fine aluminum dust has been associated with pulmonary fibrosis (HSDB, 1995). The soluble salts affect the absorption of other metals, including calcium, and lead ultimately to physiologic effects due to decreased levels of these required nutrients (Amdur et al., 1991). An oral Reference Dose (RfD) is under review by the United States Environmental Protection Agency (U.S. EPA, 1995a). Aluminum is fetotoxic to rats (Reprotox, 1995).

Cancer: The U.S. EPA has not classified aluminum for its carcinogenicity (U.S. EPA, 1995a). Although aluminum production is classified by the International Agency for Research on Cancer in Group 1: Known human carcinogen, the responsible agent(s) are probably chemicals other than aluminum (IARC, 1987a).