Air pollution levels were as much as three times lower in towns in Carmarthenshire during the early part of the coronavirus lockdown, although levels in two streets somehow bucked the trend and increased.
Nitrogen dioxide levels are measured in 91 locations across the county, with many sited at three designated air quality management areas in Llandeilo, Carmarthen and Llanelli.
Roads across the county were very quiet in April, like the rest of the UK, which generally resulted in a marked drop in nitrogen dioxide levels and led to cleaner air.
And that improves the prospect that some hotspot areas might not exceed the legal limit of 40 microgrammes per cubic metre, measured as an annual average.
Average nitrogen dioxide levels in Bridge Street, Llandeilo, in April were nearly three times lower than in March, according to a report which went before the council's executive board.
But nitrogen dioxide levels in April actually increased in Station Road, Burry Port, and Ammanford's Wind Street, compared to March.
Weather conditions play a noticeable part, with pollutants dispersed more effectively when it's windy.
The report said: "It is however clear that we have measured significant lower levels of NO2 (nitrogen dioxide) during April and May 2020 across Carmarthenshire’s AQMAs (air quality management areas), and for the first time in over seven years all monitoring sites measured a monthly reading below 40 microgrammes per cubic metre."
Levels have risen as lockdown measures eased - and Llanelli's Felinfoel Road and Carmarthen's Priory Street remain hotspots for the two towns.
The report said the data showed how much air quality could improve by reducing non-essential car journeys.
It added: "It is recommended that the council makes a commitment to expand on current policies relating to home working and agile working so not to encourage non-essential journeys when the work can be done effectively either at home or at a closer, more convenient office base.
"Air pollution is a cause of underlying health conditions that can make people more susceptible to severe health outcomes of Covid-19.
"The Covid-19 lockdown has enabled us to think about how we travel, whether we need to use our vehicles and how we can do things differently."
The slight increase in April in Station Road, Burry Port, was attributed to people still travelling to a local shop and bank - likewise for Ammanford's Wind Street, where a butchers' stayed open.
Executive board members were recommended to make a commitment to discourage non-essential journeys by council staff, and also to encourage them to use video conferencing for training and meetings where possible.
The report also noted that the main A483 trunk road through Llandeilo, which runs from Swansea to Chester, sent a lot of long-distance traffic through the town.
The executive board reiterated its disappointment in the delay of a Llandeilo bypass at a meeting on September 21.
Its Plaid Cymru and Independent members took a swipe at the Welsh Government for putting back the construction of the £51 million scheme from 2019 to 2025.
Cllr Philip Hughes said: "Before I commend this report, I think it would be remiss of me not to express my disappointment that the Welsh Government chose to withdraw the funding for the Llandeilo bypass yet again, knowing this has an effect on the air quality for people in the town and the Llandeilo area."
This was echoed by council leader Emlyn Dole and then Cllr Hazel Evans, who felt the delay was "a disgrace".
She said: "I hope they (the Welsh Government) will look at it again very quickly."
Cllr Cefin Campbell said the design of the A483 through Llandeilo had not changed, and that he had recently seen a big lorry encroach onto a pavement in order to get past a bus.
There was no discussion about Llanelli and Carmarthen - the county's other two air quality management areas.
Earlier this month, full council passed a motion criticising the Labour Welsh Government's decision to delay the bypass.
Officials are exploring short and medium-term measures to alleviate congestion and improve air quality in the town - and during the motion Labour opposition leader, Cllr Rob James, said the party was still committed to the bypass.
Cllr James said the Covid-19 pandemic had had an impact on capital projects like new roads, and said he was "extremely disappointed" that Plaid Cymru was "seeking to play party politics with this very important issue".