My Process

Building: I used pen tools to draw tle bulidings and ellipse tool to draw the circle.
Oil drum: For oil drum, i used pen tools to draw it and i make it blur.
Smoke: I use pencil tool and use stroke 8. After that, i blur them.
Oil spill: i used pen tools to draw it n blur the colour.
Oil and petrol: I used type tool to create the words.