In the past few years, as awareness of the climate crisis has grown and governments have stepped up mitigating measures, electric vehicles (EVs) have come into the mainstream. A few years ago a Tesla in a parking lot was a rare sight, but today it’s unusual if you go a day without seeing one. EV makers advertise that their vehicles are green, climate-conscious people buy them and progressive governments incentivize EV purchases with tax credits.

Are EVs actually better for the environment than gas cars? Yes. But it’s complicated. While EVs emit less carbon dioxide than gas cars over their lifetimes, they are more carbon-intensive to produce, and their batteries require minerals that are mined at an immense environmental and human cost. Electric vehicles are not a straight upgrade for our planet and its people. They are a trade-off.

EV batteries require the mining of the metals nickel and cobalt, which is highly polluting. According to an article by Wired’s Peter Yeung, much of the nickel supply comes from Indonesia. Companies clear rainforests to make space for industry; this disruption causes flooding that devastates locals. Pollutants dumped into the environment cause fish die-offs, threatening the health and livelihood of fishermen. And, of course, the mining and processing of nickel for electric cars is powered by burning coal, a dirty and toxic fossil fuel. The mining of cobalt is also destructive; according to an NPR interview with Harvard fellow Siddharth Kara, who researched mining in the Democratic Republic of the Congo (whose government is in fact authoritarian and corrupt), cobalt is extracted from massive strip mines that clear trees from the land and poison the water.

The most horrific costs of nickel and cobalt mining are the human costs. These mining industries brutalize and exploit the people who work for them. Workers in the nickel-surrounding industry in Indonesia work long days for minimal pay; many have breathing problems from exposure to toxic chemicals. Two workers burned to death in an explosion, and it has been reported that workers have fallen off buildings and been electrocuted. One time, when workers protested, security fired pellet guns at them.

The situation in the Congo might be worse. Conditions in cobalt mines are brutal, toxic, and hazardous. Human traffickers exploit children to work in the mines. Siddharth Kara told NPR, “I met mothers pounding their chests in grief, talking about their children who had been buried alive in a tunnel collapse.”

“The level of degradation, the level of exploitation is on par with old-world slavery,” Kara said.

After nickel and cobalt are mined and processed, wrecking the landscapes and the people involved, they are made into EVs, which are marketed as being clean. They are in fact cleaner than gas cars – but not one hundred percent cleaner.

According to MIT’s Climate Portal, “building a new EV can produce around 80% more emissions than building a comparable gas-powered car,” largely because of their batteries. Electric vehicles’ redemption is in the long run. Because gas cars burn gasoline for every mile and electric cars don’t, over their lifespan, electric cars produce less emissions than gas cars.

But wait! It gets even more complicated! How much better an EV is than a gas car depends on how you charge it. An EV is only as clean as the power grid you charge it from, and that varies depending on where you are. According to MIT, on average in the US, “a fully electric vehicle emits about 25 percent less carbon than a comparable hybrid car.” However, that percentage varies based on the power grid the EV is charged from. While EVs produce less emissions per mile driven than hybrids or gas cars, with the U.S.’s current power grid, they do not produce zero emissions.

So what’s the take-home from all this? It’s complicated. That’s it. The minerals in EV batteries have a severe environmental and human cost, and producing EVs creates more carbon emissions than producing gas cars. But, once the EVs are on the road, they emit less carbon over their lifetimes. All things considered, EVs are probably better in the long run; but the suffering of Indonesia and the Congo should weigh on the conscience of every EV buyer until nickel and cobalt can be sourced more sustainably.