(N/A) The symptoms observed in the villagers indicate the release of nitrogen oxides $(NO_x)$ and sulfur dioxide $(SO_2)$ from the factory chimney. These gases are produced by the combustion of fossil fuels like coal and petroleum.
In industrial processes or automobile engines,when fossil fuels are burned at high temperatures,dinitrogen and dioxygen react to form nitric oxide $(NO)$:
$N_2 + O_2 \xrightarrow{1200-1500^{\circ}C} 2NO$
$NO$ further reacts with oxygen to form nitrogen dioxide $(NO_2)$:
$2NO + O_2 \xrightarrow{1100^{\circ}C} 2NO_2$
Sulfur dioxide $(SO_2)$ is produced by the combustion of sulfur-containing fossil fuels or by the roasting of sulfide ores like iron pyrites $(FeS_2)$ or copper pyrites $(CuFeS_2)$:
$S + O_2 \rightarrow SO_2$
$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$