Refers to a brief—but not chronic—health effect. Sometimes loosely used to mean severe. Refers also to a brief, intense, short-term exposure

The settling rate of suspended particles and their penetration into the respiratory tract is in accordance with the particle AED, an expression that  accounts for the inertial and aerodynamic drag properties of particles. The AED is dependent upon the particle density, shape, and size. The particle AED is defined as the diameter of a smooth, unit density [r_o = 1 gram per cubic centimeter (g/cm³)] sphere having the same terminal settling velocity as the actual particle. The use of the AED enables one to standardize particles of different shapes, smoothness, and densities for direct comparative purposes

The most stable form of crystalline silica in the environment. The vast majority of natural crystalline is in the form of alpha-quartz

Mononuclear cells within the lung tissues that are largely scavengers, ingesting dead tissue and degenerated cells. Synonym: carrier cell, scavenger cell.

Surrounding or encompassing—usually referring to the environment in which an organism or apparatus functions

A chronic disorder of the lungs characterized by wheezing, coughing, difficulty in breathing, and a suffocating feeling, usually caused by an allergy to ingested substances.

Refers to the interaction of a non-living material with living tissues and cells (e.g., the DNA-damaging activity of silica).

Refers to a health-related state lasting a long time. Refers also to a prolonged or long-term exposure. Sometimes means low-intensity. The US National Center for Health Statistics defines a chronic condition as one lasting three months or longer.

The statistically determined, upper- and lower-bound with a 95% chance that a measurement will occur within these upper and lower values.

(see Quartz)

The proximity and/or contact with the source of a disease agent which accumulates or piles up in such a manner that the effective transmission of the agent or the harmful effects of the agent may occur.

The total amount of a material or agent to which an organism is exposed for a period of time.

The chemical molecule inside cells which carries biological information. DNA is a double stranded molecule held together by weak hydrogen bonds between complementary base pairs of nucleotides (Adenine and Thymine, and Guanine and Cytosine). This molecule carries genetic information from parent to offspring.

A fundamental pathologic process consisting of a dynamic complex of cytological and chemical reactions which occur in the affected blood vessels and adjacent tissues in response to an injury or abnormal stimulation caused by a physical, chemical, or biologic agent.

Mononuclear cells within the lung tissues that are largely (Alveolar) scavengers, ingesting dead tissue and degenerated cells.

No observed adverse effect level. A toxicological reference level to a dose, cumulative exposure level, or time weighted average— below which pathologic consequences from exposure are not expected.

Arising from, or related to, the workplace.

A thoracic air sampler for particulate matter that meets the performance criteria specified by the USEPA in 40 Code of Federal Regulations (CFR) Part 50.6 and 40 CFR Part 53. The performance criteria includes a collection efficiency of 100% for particles of 0 to 1�m aerodynamic equivalent diameter (AED), 89.3% of 4�m AED, 55.1% at 10�m AED, 50.9% at 10.5�m AED, 4.1% at 15�m AED, and 0% at 16�m AED. The performance criteria are such that this type of sampler is more like a thoracic air sampler rather than a respirable air sampler.

Composed of separate tiny masses of material or particles.

Inflammation of the lungs.

A form of hexagonal crystalline silica or silicon dioxide (SiO₂) occurring in abundance, most often in a colorless, transparent form, but also sometimes in colored varieties used in semi-precious stones. The principal constituent of ordinary sand.

The portion of an aerosol that is capable of entering the gas exchange regions of the lungs if inhaled. By convention, a particle-size fraction of the total airborne dust with aerodynamic diameters less than approximately 10�m and having a 50% deposition efficiency for those particles with an aerodynamic diameter of approximately 4�m.

The probability that an undesirable outcome will occur. Risk in this context is defined in terms of the probability of a particular adverse effect occurring. It has the dimensions of frequency of incidence (e.g., 1 in 1,000,000) and is coupled to an exposure estimate. The actual risk statement may be made in the form of the probability of an outcome associate with a unit exposure. For example, there is a lifetime "risk" of 2.5 excess cancers in 10,000 from an exposure to 1 part per million of a chemical in community air breathed 24 hours per day, every day for 70 years.

A strong, hot, dry persistent northwest wind that occurs in Kuwait most often in summer and frequently is accompanied by dust storms, especially in the southern part of the country.

That portion of the respiratory tract that includes the lungs, both the conducting airways (tracheobronchial region) and the pulmonary region (alveolar region where gas exchange occurs). Particles that penetrate into the thoracic region will deposit either in the tracheobronchial region or the pulmonary region, depending upon the particle AED and the collection efficiency of the respiratory tract for a given particle AED. If the thoracic size particles are small enough (about 10 �m AED or less), then they may penetrate into the pulmonary region with greater efficiency.

Total suspended particulate, referring to the entire range of ambient air matter that can be collected, from the sub-micron level up to 50 �m in aerodynamic diameter.