Table V. Modified ISO and ISO TEM Size-Specific Exposures Indices Using Second Laboratory Data: Estimated TEM (f/cc) Exposure for a Measured PCM Exposure of 1.0 f/cc^*.

Fiber exp. Index	Approximate fiber dimensions used for simulations	Zone 1		Zone 9
		ISO method	Modified ISO method	ISO method	Modified ISO method
Stanton	Dia. <0.25 μm	Mean: 1.00	Mean: 1.15	Mean: 1.49	Mean: 1.47
	Length ≥5.0 μm	Range: 0.71–1.33	Range: 0.82–1.62	Range: 1.10–2.01	Range: 0.97–2.50
	Aspect Ratio ≥3:1	Std Dev: 0.084	Std Dev: 0.110	Std Dev: 0.139	Std Dev: 0.171
		95% CI: 0.85–1.16	95% CI: 0.95–1.37	95% CI: 1.24–1.78	95% CI: 1.17–1.84
Pott	Dia. <1.0 μm	Mean: 3.33	Mean: 3.04	Mean: 3.93	Mean: 3.69
	Length >3.0 μm	Range: 2.43–5.12	Range: 2.14–4.53	Range: 2.99–5.23	Range: 2.65–5.74
	Aspect Ratio ≥3:1	Std Dev: 0.333	Std Dev: 0.318	Std Dev: 0.322	Std Dev: 0.402
		95% CI: 2.75–4.05	95% CI: 2.48–3.75	95% CI: 3.35–4.63	95% CI: 2.99–4.55
Modified Lippmann	Diameter >0.15 μm	Mean: 0.23	Mean: 0.25	Mean: 0.30	Mean: 0.24
	Length >15.0 μm	Range: 0.14–0.33	Range: 0.16–0.36	Range: 0.20–0.42	Range: 0.12–0.44
	Aspect Ratio ≥3:1	Std Dev: 0.026	Std Dev: 0.029	Std Dev: 0.034	Std Dev: 0.037
		95% CI: 0.18–0.28	95% CI: 0.19–0.31	95% CI: 0.23–0.37	95% CI: 0.17–0.32

^*Predicted size-specific exposures for each exposure index based on a measured PCM concentration of 1.0 f/cc. Approximate 95% confidence intervals were calculated using the bootstrap percentile method.