An explosives expert tells an inquest he has been unable to find any literature warning of the dangers of smoke from fireworks to drivers.
Andrew Gregg, who passed the scene of the fatal pile-up in 2011, told the inquest he had not seen fog like it in his job "for a long time."
Drivers have told an inquest of their horror at being involved in one of the worst British motorway pile-ups in living memory.
The barrister representing the fireworks operator at the Taunton Rugby club display said to the meteorologist, Dr Jonathan Taylor, that the air in the town that night was already contaminated before that display got underway.
Dr Taylor agreed with Adrian Darbishire QC and also confirmed that, although scientists like him carry out research in part to help curtail hazards from occurring, there was no literature to be found linking the dangers of firework smoke and humidity.
Mr Darbishire suggested pollution from another fireworks display in Taunton may have also been carried to the crash site.
Dr Taylor said this could possibly be the case. He was asked if the rugby club display had any affect on the obscuration of the motorway and said it wasn't possible to say.
The West Somerset coroner has been questioning a meteorologist at the inquest into the death of seven people in a crash on the M5 in 2011.
He asked Dr Jonathan Taylor from the Met Office if it was possible to get get thick fog without contamination.
Dr Taylor replied that there will be particles in the atmosphere for instance as was experienced last week with pollution from the continent impacting the eastern part of the UK.
The coroner followed up by asking if there were any known works to warn of the danger of fireworks displays and humidity.
Dr Taylor said there would not be, but that as a meteorologist he would know the link. He said that the more particles there are in the air the greater the reduction of visibility such as from a firework display.
Dr Jonathan Taylor from the Met Office has told the inquest he was asked by Avon & Somerset Police to compile a report on the impact of firework smoke on humidity and visibility.
The Strategic Head of Observation from The Met Office also told the inquest no relevant studies had ever been undertaken to assess the correlation.
He said visibility may have been reduced to around seven metres if the firework smoke mixed with 100% humidity in the air.
Had there been no contamination in the atmosphere at all then visibility would have been 414 metres.
Dr Taylor, pointed out it is all based on modelling as there are no actual figures on the level of contamination at Taunton that night nor the level of humidity.
The inquest into the deaths of seven people in a motorway crash on the M5 has today heard from driver, Sheila Orrell.
The motorist from from Bath described her journey South on the M5 on the night of the crash in November 2011 as a white knuckle ride and her worst journey on the M5 ever.
She told the inquest that a combination of fog, spray from lorries and the speed of drivers was adding to the horrendous conditions.
Dozens of homes and businesses had to be evacuated earlier today after a fire in a gas main on the main road at Norton Fitzwarren near Taunton.
Police set up a 250 metre exclusion zone around the blaze, on the B3227 to Wiveliscombe.
It's understood it started in an area where roadworks were taking place. The area has now returned to normal. Peter Frearson is from Wales & West Utilities:-
The gas main caught fire outside McColls newsagents in Norton Fitzwarren. The fire service are on the scene.
Police say a neighbouring industrial estate is also being evacuated. People are being taken to the Ring of Bells pub.
Homes have been evacuated following a fire in a gas main on the main road at Norton Fitzwarren near Taunton.
Police have set up a 250 metre exclusion zone around the blaze which is on the B3227 to Wiveliscombe.
It is understood the blaze started in an area where roadworks were taking place. There are no reports of anyone being hurt.
Police collision investigators say the band of reduced visibility at the time of the crash which killed seven people on the M5 in November 2011 was at least 110 metres thick.
One survivor said his car was hit so many times 'it was like being in a pinball machine'.
While a driver said he drove into what 'appeared to be a scrap yard.'