Before a drill can penetrate the solid rock beneath the ocean bed, it must be lubricated. Many companies use oil-based or synthetic-based lubricants that protect drills from breaking as they chip through many layers of rock. As the rock and underlying clay make contact with the drill and its lubricant, large splinters called "cuttings" are formed and discharged many hundreds of meters from the drill-site. The lubricants typically contain lead, arsenic, copper, barium, chromium, cadmium, mercury, iron and zinc. Their presence increases toxicity, affecting the abundance and diversity of marine life.
Many leaks are caused by corroded pipes and human error. Most are minimal and are fixed without causing a large-scale disaster. A "blowout" occurs when a drill unexpectedly penetrates a gas pocket, causing an explosion. Crude oil is leaked into the ocean continuously until the leak is fixed. This can take hours or weeks. The massive spill in the Gulf of Mexico in the spring and summer of 2010 was caused by a blowout. Chemicals associated with heavy machinery, such as grease, diesel, detergents, corrosion inhibitors, bleach and cleaning solvents are constantly present on a rig deck and are often drained into the ocean, increasing the toxicity of the water.
Marine life that become coated in crude oil can die from mechanical smothering. Birds' feathers lose their waterproofing, causing them to die from hypothermia. Many breeds of fish and marine mammals die after ingesting oil-coated food. Farther away from a spill, animals become disoriented and exhibit other behavior changes after breathing volatile organic compounds carried by ocean currents.
Organisms living around oil wells are constantly exposed to complex toxic substances associated with drilling. Immune systems are compromised, and genetic mutations occur. Reproductive cycles are disrupted for months in areas subject to leaks and spills. Many of these toxins bio-magnify, or increase in concentration, as they move up the food chain toward humans.