Colorado dad and Denver-area anesthesiologist Tim Farnum has always understood the intrigue of modern technology. Smartphones, tablets and unfettered Internet access connect us to faraway corners of the world and make life – and movie watching – all the more convenient.

But the father of five is not convinced these devices are beneficial for children, a conclusion he came to after his two youngest sons, ages 11 and 13, got smartphones last year.

“There were some real problems,” Farnum, 49, told The Washington Post. “If you tell them to watch the screen time, all of a sudden the fangs come out.”

As he tells it, his once energetic and outgoing boys became moody, quiet and reclusive. They never left their bedrooms, and when he tried to take away the phones, one of Farnum’s sons launched into a temper tantrum that the dad described as equivalent to the withdrawals of a crack addict.

So Farnum started researching the side effects of screen time on kids and found statistics that astonished him. Too much technology too soon can impair brain development, hinder social skills and trigger an unhealthy reliance on the neurotransmitter dopamine, a high similar to what drug and alcohol addicts feel.

Farnum read it all, then said he thought to himself: “Someone has got to do something.”

In February, he formed the nonprofit PAUS (Parents Against Underage Smartphones) with a few other medical professionals and began drafting a ballot initiative that, if passed, would make Colorado the first state in the nation to establish legal limits on smartphones sales to children.

Farnum’s proposal, ballot initiative no. 29, would make it illegal for cellphone providers to sell smartphones to children under the age of 13. The ban would require retailers to ask customers the age of the primary user of the smartphone and submit monthly adherence reports to the Colorado Department of Revenue.

The department would be responsible for creating a website portal for the reports and would investigate violations and collect penalties. The first violation would incur a written warning. A second would produce a $500 fine, and the amount would double with each subsequent incident.

The initiative has garnered “overwhelming” support from parents and grandparents who worry that too much technology can stunt imaginations and appreciation for the outdoors, he claims. But Farnum also faces opposition from others, including some lawmakers, who believe that it’s a parental responsibility, not one for government.

“Frankly, I think it should remain a family matter,” Colorado state Sen. John Kefalas, D-Fort Collins, told the Coloradan. “I know there have been different proposals out there regarding the Internet and putting filters on websites that might put kids at risk. I think ultimately, this comes down to parents . . . making sure their kids are not putting themselves at risk.”

Farnum told The Post he understands the pushback from those who see this as a parental responsibility and a law as an encroachment on parental power, but said his group sees premature smartphone access as a danger equivalent to smoking cigarettes, drinking alcohol or watching pornography.

“We have age restrictions on all those things because they’re harmful to kids,” Farnum said. “This is no different, in my opinion.”

The proposal also distinguishes smartphones from other cellular devices like standard flip phones that cannot access the Internet, because many parents just want to be able to contact their children for safety reasons.

Though the goal is to curb what Farnum described as the corporate interest of cellphone companies and app makers from latching onto the younger generations, he admitted that there is also an educational component of his crusade. Many parents don’t know the dangers of excessive technology usage, he said, or the permanent damage it can do to their children.

Because iPads and tablets are even entering the classroom at an earlier age, Farnum said it is a “real struggle” for parents to feel like they have control over their children’s exposure to technology.

“Hopefully this helps and pushes the conversation forward,” Farnum told The Post.

The nonprofit has cleared some of the initial hurdles that come with proposing new legislation, but still has a long road ahead. PAUS will need to collect roughly 100,000 signatures over the next year and a half to get the issue on the ballot in the fall of 2018.

By the end of June, Farnum plans to have the official petition printed and ready for signatures. Colorado does not accept digital petition signatures, so Farnum and his group will have to collect support the old-fashioned way.

“It’s kind of ironic, perhaps,” he said. “We’re going to have to go knock on doors and sit outside grocery stores. It’s slowly gaining steam.”

Next week, Farnum, who characterizes his views as “fairly libertarian,” is meeting with the most liberal democratic senator in the state. But he is trying to keep the initiative away from partisan politics.

“I think it’s good that we’re all going to get to vote on it,” he said. “The parents all have to come together and do this.”

At home, Farnum’s two young sons no longer have smartphones – at least for now. They spent much of their second semester of the school year nearly technology free, and he says he saw a notable difference.

They laughed again and wanted to be outdoors.

One, Farnum recalled, even offered a striking admission: “‘Hey dad, I really like reading now.'”