Air quality index from charcoal production sites, carboxyheamoglobin and lung function among occupationally exposed charcoal workers in South Western Nigeria

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Table 7 Correlation between the quantitative variables

Pearson correlation coefficient Sig (2 tailed)	NO₂	SO₂	CO	CO₂	PM_2.5	COHb	FEV₁	PEFR	Body mass index
NO₂	1
SO₂	0.181** 0.000	1
CO	0.477** 0.000	0.390** 0.000	1
CO₂	0.261** 0.000	0.422** 0.000	0.525** 0.000	1
PM	0.441** 0.000	0.212** 0.000	0.717** 0.000	0.261** 0.000	1
COHb	0.074 0.586	−0.169 0.209	0.104 0.441	0.038 0.781	0.320* 0.015	1
FEV₁	0.036 0.789	−0.144 0.286	−0.173 0.199	−0.005 0.973	−0.027 0.843	−0.075 0.577	1
PEFR	−0.017 0.902	−0.140 0.300	−0.077 0.571	0.024 0.859	−0.082 0.545	−0.122 0.367	0.875** 0.000	1
BMI	−0.071 0.599	0.061 0.655	−0.116 0.392	−0.010 0.943	−0.144 0.284	−0.038 0.777	0.328* 0.013	0.279* 0.036	1

* Correlation is significant at the 0.05 level (2-tailed); ** correlation is significant at the 0.01 level (2-tailed)