. 2013 Sep 16;8(9):e74435. doi: 10.1371/journal.pone.0074435

Table 3. Adjusted^a incidence rate ratios for primary brain tumour in association with a 100 Bq/m³ increase in domestic radon^b within strata of NO_x at the residential address.

Potential effect modifier	Cases, n	IRR (95% CI)	P^c
NO_x at front door (µg/m³)^d
<21.6	58	2.53 (1.06–6.04)	0.15
≥21.6	63	0.98 (0.39–2.50)

We adjusted the analyses for age (underlying time scale), sex, employment in the chemical industry for at least one year and consumption of fruit and vegetables.

Radon exposure was entered as a continuous variable in all models as the time-weighted average concentration at residences from 1. January 1971 until censoring.with inclusion of a 10 year latency period.

Test of the null hypothesis that the linear trends are identical, for Wald test for interaction.

Time-weighted average concentration for NO_x.

Table 3. Adjusteda incidence rate ratios for primary brain tumour in association with a 100 Bq/m3 increase in domestic radonb within strata of NOx at the residential address.

Table 3. Adjusted^a incidence rate ratios for primary brain tumour in association with a 100 Bq/m³ increase in domestic radon^b within strata of NO_x at the residential address.