Expenses a company has when it drills for oil or natural gas. Intangible drilling costs are sometimes convenient for a company's tax purposes because it can deduct intangible drilling costs in one year when the company perhaps found little or no oil from profits made in a different year when the company does find oil.
Bruce Lanphear, a professor at Simon Fraser University and also an expert in lead toxicity, said Edwards not only studies the impact of lead in water, but he makes his testing available to communities in need, like he did in Flint.
But 15 ppb is a regulatory measure, not a public health one. Researchers stress that there is no 100 percent safe level of lead in drinking water, only acceptable levels. Even levels as low as 5 ppb can be a cause for concern, according to the group studying Flint's water.