Table 2 Pearson correlation (r) between the counts of three types of illnesses and predictive variables (Data in December, January and February were excluded); p represents p-value and n represents the sample size. Bolded results represent significant correlations at the level of 0.001

School days (yes/no)

r

0.166

0.537

−0.461

p

< 0.001

< 0.001

< 0.001

n

1100

1100

1100

Holiday (yes/no)

r

− 0.028

0.052

0.087

p

0.348

0.087

0.004

n

1100

1100

1100

O₃

r

−0.056

−0.218

0.357

p

0.066

< 0.001

< 0.001

n

1100

1100

1100

SO₂

r

0.030

0.095

−0.135

p

0.320

0.002

< 0.001

n

1100

1100

1100

NO₂

r

0.112

0.045

−0.158

p

< 0.001

0.129

< 0.001

n

1100

1100

1100

CO

r

0.052

0.219

−0.135

p

0.084

< 0.001

< 0.001

n

1100

1100

1100

PM_2.5

r

−0.176

−0.182

0.264

p

< 0.001

< 0.001

< 0.001

n

1100

1100

1100

Daily precipitation

r

0.001

−0.053

−0.081

p

0.971

0.080

0.007

n

1100

1100

1100

Daily mean temperature

r

−0.214

−0.450

0.561

p

< 0.001

< 0.001

< 0.001

n

1100

1100

1100

Cyanobacteria concentration (maximum from 5 pixels)

r

0.150

0.152

−0.200

p

0.013

0.012

0.001

n

273

273

273