Damien McNamara has been studying the effects of blue light from streetlights after it severely impacted his son's health.

The father of a 12-year-old autistic boy says sudden exposure to a new street light installed outside his bedroom had a perilous impact on his health.

Damien McNamara shared Reuben's story at the New Zealand Starlight Conference in Tekapo last week where his story was well received by experts in the audience.

While there has been no scientifically proven effects of light on autism, academics agree it is worth further study.

Supplied Four weeks before Reuben's behaviour reached a critical point, NZTA had replaced the streetlight outside his bedroom with a 114 watt 4000 kelvin bulb.

McNamara has been campaigning for darker skies but now he is spurred on by the bigger impact of light pollution on his son Reuben's health.

Reuben has high-functioning autism, has always found it hard to cope with change and is prone to tantrums.

In late 2017 his behaviour spiralled to the point he was actively trying to hurt himself and showing violent tendencies at school, Damien McNamara said.

His behavioural problems began to present a month after a 114-watt LED streetlight was installed 12 metres from his bedroom window.

McNamara measured the strength of the light inside his son's window, and found they were far higher than recommended levels agreed upon by councils.

"It's obvious light pollution, light glare and light spill onto private property."

McNamara, an amateur astronomer and president of the North Otago Astronomical Society, learned about the link between blue light, part of the light spectrum which is more prevalent in 'cold' white lights, and the hormone melatonin, which helps to regulate the body's 24-hour clock.

JOHN BISSET/STUFF McNamara is interested in the effects of light, especially blue light, on his son's health.

An analysis of multiple studies into melatonin in autism spectrum disorders (ASD) found it was associated with better sleep and better daytime behaviour but said additional studies were needed to confirm this.

The family moved house three months ago and within three weeks Reuben's behaviour had improved, McNamara said.

In recent years, councils and NZTA have been replacing high pressure sodium streetlights with the more environmentally friendly LEDs but a new issue has arisen around the warmth of the lights.

JOHN BISSET/STUFF McNamara uses a spectral grader to look at the different colours in lights and show how much blue light we are exposed to.

​NZTA regulations say road lighting should be 4000 kelvins (the measurement of light temperature) although some councils have agreed concessions for the use of warmer 3000k lights to limit light pollution in special areas.

McNamara said while the streetlight was too close to be able to get an accurate blue light reading, from outside Reuben's window he was able to detect blue light from 186m away on SH1 and 320m away on local authority roads.

McNamara has since spent two years investigating light and glare and believes NZTA need to start taking notice of research being done.

"I was on my way to work one day and it had been raining and, as most SH1 surfaces are, it was nice and smooth so I took my spectral grating [a device used to see the spectrum of colours in a light] out," he said.

"Not only was I able to detect blue light from the lights, I could detect blue light from the reflection, so we are not only getting blue light shining down on us, but it's reflecting back up again."