Crude oil consists mainly of hydrocarbons, as well as many other elements (from iron and mercury to oxygen and xylene). Some crude oils are light and volatile, which makes them very toxic to humans; others are heavy and sticky, which makes them less fluid and therefore less toxic when contained. However, when spilled across large surfaces, they easily endanger water- and land-based life in the affected areas.
Crude oil cannot be used as such; rather, it needs to be refined and separated into various types of petroleum products. When refined, the crude oil paradoxically yields a slightly higher quantity of refined product.
Out of these refined products come some of the most common items in contemporary life: eyeglasses, vitamins, umbrellas, candles, detergents, band-aids, CDs, clothes, fertilizers etc.
The toxic effects of crude oil on humans include: