England and Wales have taken a huge step toward creating a healthier world for future generations of its citizens by banning smoking inside cars with children under 18 years old.

In what is being called the most important anti-smoking measure since the 2007 ban of smoking at work and in enclosed public spaces, smokers who light up with children inside their car will soon face a fine as England and Wales carry out anti-smoking measures that seek to improve the overall health of future generations. The law, which went into effect on Thursday, is not expected to be heavily enforced until the police believe that the general public is more aware of it. The National Police Chiefs’ Council said in a statement that the police would be “taking an educational, advisory and non-confrontational approach when enforcing the new legislation.” After three months, however, the police will stop handing out warnings and start handing out the 50-pound fines (about $75).

Secondhand smoke can be devastating to the still-growing lungs of a child. Studies have found that exposure to secondhand smoke doubles risk of hospitalization in kids with asthma, and may even cause behavioral issues to develop, particularly emotional and conduct disorders. Furthermore, a report from the Centers for Disease Control and Prevention (CDC) found that teens who’d never smoked before were 1.4 to 2.1 times more likely to begin smoking when exposed to secondhand smoke.

The new law details exactly how people will be subject to a fine if they’re caught smoking in their car. For example, if a driver is smoking in the car with a child under 18, they’ll receive the $75 fine. However, if the driver and one of their passengers is smoking inside the car with a child under 18, then both will get fined. This will be enforced even if the driver and passengers are smoking with the windows down and the sunroof open. Convertible drivers, meanwhile, will be happy to find out that they can smoke freely with a minor in the car as long as the convertible top is down and properly secured.

While opponents of the ban argue it’s unenforceable, supporters have hailed it as one of the most important step toward public health since the 2007 bans went into effect. “Changing the law can often feel like an endless struggle, but this has been an incredible journey,” Penny Woods, chief executive of the British Lung Foundation, wrote in a statement. “It’s taken just five years to persuade the government that this ban is vital to protect the health of our children.”

Many countries have found banning smoking in certain areas to be effective at curbing smoking rates. For example, the CDC found that when smoking was banned in the workplace and in enclosed public spaces throughout Ireland and Scotland, health conditions improved in as little as two months. Stateside, in New York, the 2004 law banning smoking in restaurants and bars resulted in an eight percent drop in acute myocardial infarctions, saving the city millions in health care costs.