Soil tests carried out in the vicinity of last month’s landfill fire have come back all clear.

However, the authorities are stumped after toxic residues were found unexpectedly in an area not thought to have been affected by the plume.

The Environment and Resources Authority had commissioned the soil tests after waste from black and grey bags caught fire in a massive blaze at the Wasteserv plant in Magħtab on August 31.

The fire prompted a public health hazard alarm, with large swathes of the island put on alert by the health authorities about the possible impact of the fumes and residues from the large plume of black smoke.

The health authorities had also urged civilians to wash any locally grown fruit and vegetables after the fire, for fear that they may have been covered in harmful residues from the blaze.

Mark Scerri, one of ERA’s senior environment protection officers, told The Sunday Times of Malta that favourable weather conditions and the nature of the fire itself had resulted in the least possible contamination to the soil layer. 

He explained that the fire burnt at such a high temperature that the main types of residues that authorities were concerned about had not been created. This was coupled with favourable weather conditions, which saw the large plume of black smoke rise up and over the landfill and eventually blow away relatively quickly.

The main risk of exposure to the pollutants from such fires, Mr Scerri said, was through what is known as a plume fallout and the accumulation of harmful particles that can come down like a grey snow over residential and agricultural areas. 

“In fact, ERA’s response in the aftermath of the incident focussed on soil sampling in a quadrant of land 50 square kilometres downwind from the site of the fire in order to assess the possibility of risks to the general public,” Mr Scerri said.

 The authority, he explained, had commissioned a German company specialised in the analysis of what are known as persistent organic pollutants – the harmful residue that can spread after a large fire.

The results of the tests, Mr Scerri said, had shown that the concentration of these persistent organic pollutants in the ash samples from the site itself as well as in the soil samples from the areas downwind of the landfill, were well below the tolerable limit for children’s playgrounds.

This limit, he said, was the strictest for these kinds of pollutants in soil, because it was meant to protect children from coming into contact with even miniscule amounts.

Although these soil tests came back clear, the authority told The Sunday Times of Malta that they were concerned about the results from another parcel of land not too far from the fire. 

Mr Scerri said one seven square kilometre area around Naxxar and Lija – which should not have been affected by the fire – had come back with readings for two types of chemicals that required further testing.

Known as dioxins and furans, these toxic chemicals are normally found in very small amounts in the environment. Their presence is increased as a result of combustion.

 Exposure to the chemicals has been associated with a wide range of adverse health effects in laboratory animals and humans. And, the seriousness of their impact on health depends on the level and duration of exposure.

Asked what he believed could cause these chemicals to appear, Mr Scerri was reluctant to comment, saying it could be the result of a host of different activities. 

“At this point it is difficult to say, but I can confirm that it is a matter of interest to us here at ERA,” he said. 

On Thursday the Times of Malta reported how air quality monitors had recorded no spike in pollution during the landfill fire, raising concerns about the system’s accuracy.   

The government sources had said they were surprised how no special air monitoring had been carried out in the area after the fire, which had covered several localities in a dark cloud. They were even more concerned about how the established monitoring centres had shown normal readings for the entire day.

But the authority insists that there was no spike in the readings because of meteorological conditions. It also stressed that its monitors were well calibrated. 

ERA said its monitoring station network was composed of sites in Żejtun, Msida, Attard, Xemxija and Għarb. None of these had been directly in the plume’s line of flight. And the Żejtun station – the closest to the direction the smoke was travelling in, had not registered any spike, probably due to the distance from the fire, approximately 14km.

Even if civilians had been exposed to fumes from this fire, the ERA said, this would have only been for a short period. While this was not ideal, the authority said civilians should be more concerned about the regular exposure to these harmful chemicals – such as through smoking tobacco.