Table 5.

Dosimetry Calculations for GaAs in the workplace.^a

1. GaAs exposure calculation premised on detecting As concentration of 2.7 mg/m3 in the workplace

$$\frac{2.7(\text{mg As})}{{\mathrm{m}}^3}\times \frac{144.645(\text{g GaAs}/\text{mol})}{74.92(\text{g As}/\text{mol})}=5.2(\text{mg Ga As})/{\mathrm{m}}^3$$

2. Calculated weekly nanoparticles lung deposition (mass) in a worker exposed to 5.2 [mg/m] GaAs

Assumptions:

· Ventilation rate of a healthy human adult: 20 [L/min]

· Deposition fraction: 30%

· Weekly exposure period: 8 [h/day], 5 [d/week]

Weekly lung deposition:

$$\frac{5.2\text{mg}}{{\mathrm{m}}^3}\times \frac{20\mathrm{L}}{\text{min}·\text{person}}\times 30\%\times \frac{60\text{min}}{\text{hour}}\times \frac{8\text{hour}}{\text{day}}\times \frac{5\text{day}}{\text{week}}\times \frac{{\mathrm{m}}^3}{1000\mathrm{L}}=74.88\text{mg}$$

3. Weekly deposition level converted to mass/surface area in the human lung

Assumptions:

· Human alveolar surface area: 102 [m /person]

Calculation:

$$\frac{74.88\text{mg}}{\text{person}·\text{week}}\times \frac{\text{person}}{{102\mathrm{m}}^2}=\frac{1000\mathrm{\mu }\mathrm{g}}{\text{mg}}=734.12\mathrm{\mu }{\mathrm{g}/\mathrm{m}}^2$$

4. Comparable deposition level in a mouse receiving a one-time installation exposure

Assumptions:

· Alveolar epithelium surface area of a mouse: 0.05 [m /mouse];

· Weight of a mouse: 25 [g]

Calculation:

$$\frac{734.12\mathrm{\mu }\mathrm{g}}{{\mathrm{m}}^2\cdot \text{week}}\times \frac{0.05{\mathrm{m}}^2}{\text{mouse}}\times \frac{1\text{mg}}{1000\mathrm{\mu }\mathrm{g}}\times \frac{\text{mouse}}{25\mathrm{g}}\times \frac{1000\mathrm{g}}{\text{kg}}=1.468\text{mg}/\text{kg}$$

^aOur animal experiments were based on a real-life As exposure measurement in a manufacturing facility, where airborne As levels were documented to be as high as 2.7 mg/m³.³⁴ The chosen dose of 0.014 mmol/kg for each of the III-V materials equals to 1–4 mg/kg based on the molar weight in Table 3, which overlaps with the calculated mouse exposure dose of 1.468 [mg/kg].