TLV®s for dusts may be reported in which of the following units?

The correct choice of units for reporting TLV®s (Threshold Limit Values) for dusts is milligrams per cubic meter (mg/m³). This unit is appropriate because it directly measures the concentration of a substance in the air, which is essential for assessing exposure levels in occupational settings. Dusts are typically solid particulate matter that can be suspended in the air, and measuring their density in terms of mass per volume (mg/m³) allows for an accurate evaluation of potential inhalation risks.

Using mg/m³ indicates how many milligrams of dust are present in a specific volume of air, facilitating direct correlation with human exposure. This unit is widely utilized in industrial hygiene and toxicology when evaluating conditions in workplaces, particularly where respiratory exposures to particulates are a concern.

The other units mentioned, such as parts per million (ppm) based on mass or volume, and kilograms by mass, are less relevant for dust reporting. Ppm units could be suitable for gases in air but may not be practical for quantifying solid dust particulates effectively. Kilograms by mass is also not used for exposure scenarios where concentration in the air is critical. Thus, mg/m³ is the most relevant and effective unit for this purpose.