Environmental compliance at Scotland's industrial sites has dropped for the first time in three years.
The Scottish Environment Protection Agency (Sepa) said only 90.5% of regulated sites were rated "satisfactory" in 2018, a fall of 0.5%.
There are ongoing concerns over the petrochemical operations at Grangemouth and Mossmorran.
A restart caused a massive unplanned flaring at ExxonMobile’s Mossmorran site on 13 February.
Ineos Forties Pipeline at Grangemouth was rated "very poor".'
The facility has been non-compliant since 2014 because of flaring from its towers and excessive discharges of effluent.
Sepa issued a final warning notice to the operator in 2018, but it says investment in new ground flares and an effluent treatment plant are expected to produce improvements.
The Compliance Assessment Scheme assesses whether sites are meeting the conditions of their environmental permits.
The licenses determine the control measures which are necessary in industrial processes to minimise the risk of pollution or environmental damage.
All of Scotland's nuclear sites are rated "excellent", but ExxonMobil at Mossmorran in Fife is "poor".
A record number of complaints have been received by Sepa from residents living close to the plant.
Repeated flaring incidents have caused significant light and noise pollution which many say is affecting their quality of life, according to the BBC.
ExxonMobil has appealed the "poor" rating it has received and has asked Sepa for the "evidential data on which it has made its assessment".
An adjacent facility operated by Shell has improved to "excellent" from "good".
Chief executive of Sepa, Terry A'Hearn, told the BBC: "Whilst recognising successes, we're also clear on our strategy to tackle consistent non-compliance.
"We have already refocused resource on tackling poor performance at complex industrial sites and will this year start to see the first in a series of significant investments by operators that aim to improve environmental outcomes for communities."
"That combined with a newly established dedicated enforcement unit will focus of the most serious non-compliance.”
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