In 2010, a two-year-old Indonesian boy named Aldi Suganda made headlines when a video showing him smoking went viral.

The poor kid was reportedly so addicted to nicotine that he was smoking up to 40 cigarettes a day, and would throw tantrums and hit his head against the floor whenever his parents tried to get him to cut back.

Although that’s a very extreme case, it clearly shows how harmful smoking can be to a kid's mental and physical health — and that's true even when the exposure is strictly from secondhand smoke.

A new study published in the Journal of Child Psychology and Psychiatry, which looked at more than 1,000 children, backs this up.

Researchers found that kids exposed to secondhand cigarette smoke in the first four years of life (even if their mom didn't smoke while pregnant) are more likely to develop signs of hyperactivity and other behavioral problems.

That's because the smoke affects brain development in regions related to hyperactivity and impulsivity.

This adds to other smoke exposure-related health problems among young kids, including lower respiratory tract infections, severe asthma attacks, ear infections, and sudden infant death syndrome.

When it comes to secondhand smoke, there is no such thing as a risk-free level of exposure (for kids or adults). And thirdhand smoke — residue in upholstery, clothing, etc. — is also toxic.

The bottom line: Keep your home a smoke-free environment, and avoid spending time in places where smoking is permitted. Do not permit anyone to smoke around your children.