people; breathe; pollute; air; pollution; contaminate; harmful; poisonous; face; inhale; respiratory; all; time; clock; smoke; chimney; industrial; emission; discharge; carbon dioxide; CO2; quality; problem; cause; condition; impact; health; risk; realize; awareness; concern; save; environment; vector; illustration; concept; outline; flat; graphic; design; icon; sign; symbol; abstract; metaphor; background; isolated; element; circle; black –