The company’s second-quarter results on Wednesday, as well as comments by Alcoa executives on a conference call, revealed new information about how the steel and aluminum tariffs were hurting the very companies they were intended to protect.

About half of Alcoa’s sales are booked in the United States, but a smaller share of its assets are in the country. The Trump administration’s tariffs hit Alcoa when it sells aluminum produced in its overseas plants, predominantly those in Canada, to customers in the United States.

On a call on Wednesday to discuss second-quarter earnings, Alcoa's chief financial officer, William F. Oplinger, said the aluminum tariffs, which the Trump administration set at 10 percent, would increase Alcoa’s costs as much as $14 million a month. Alcoa’s total hit this year could total around $100 million.

That’s about 12 percent of the $822 million in pretax profits that Alcoa made in the first half of the year It’s sizable, but not a crippling blow.

But the tariffs also come at a time when other factors are weighing on Alcoa’s business.

The company on Wednesday reduced by $500 million its 2018 forecast for adjusted earnings before interest, taxes, depreciation and amortization, a profit measure that excludes several expenses. The estimated hit from the tariffs accounts for around 20 percent of that reduction, but the company also blamed the lowered forecast on changes in market prices, higher energy costs and operational issues.