The conclusions are stark. The fire that began in a single flat and engulfed all 24 storeys of Grenfell tower, killing 72 in the process, spread a cocktail of contaminants that may harm the health of residents, clean-up workers and emergency services for years to come.

The blaze released a plume of noxious gases including carbon monoxide and hydrogen cyanide. In that plume were fine particulates that damage the lungs, and known cancer-causing substances and irritants from benzene to polyaromatic hydrocarbons (PAHs).

When Public Health England monitored the air around Grenfell some weeks after the fire, it found undetectable levels of dioxins and furans, both harmful products of the blaze. But that is unsurprising, says Prof Anna Stec, who led the new analysis of contaminants around Grenfell. They had long been dispersed by the wind.

A more pressing question was how contaminated the homes and other buildings were, and the ground people used in between them. Stec’s analysis shows that the places where people live and work, where they walk and play, were heavily contaminated by the rich mix of toxicants released by the blaze. The chemicals can be absorbed through the skin, inhaled or ingested, and then spread in the body.

The health risk from soil contaminants is assessed by comparing them to guideline levels. The higher the level is above the guideline, the greater the likelihood that it will harm people, and the more urgently it needs to be investigated. At Grenfell, soil collected 27 metres from the tower six months after the fire contained 130 mg/kg of benzene. That is at least 40 times greater than the guideline level for residential land.

The level drops off with distance from the tower, but in another soil sample collected 142 metres from the site, again six months later, the benzene level stood at 100mg/kg, 30 times the guideline level. The figures mean that both sites are considerably more contaminated than what is expected on the commercial land around petrol refineries.

Other contaminants were found in high concentrations in the ground around Grenfell. In the soil taken 27 metres from the tower, the level of the most toxic PAH, benzo(a)pyrene or BaP, was more than five times higher than the guideline figure for residential land. Once inside the body, BaP and other PAHs accumulate in fatty tissues and organs, where they can damage the lungs and depress the immune system. Last year, Stec reported that firefighters who absorbed PAHs through their skin were at greater risk of developing cancer.

The noxious substances released by the fire did not just infiltrate the soil, but coated buildings and balconies. Seventeen months after the fire, an oily substance swabbed from a window blind on a flat 160m away tested positive for isocyanic acid, ethyl isocyanate and propyl isocyanate. The chemicals, typically released by burning furniture and the insulating foams used to protect towers, can trigger asthma, rashes, swelling and lung inflammation.

The scientists point out that the study could have been more valuable had it been set in train in the immediate aftermath of the fire. But, even months after the event, the findings reveal widespread contamination of homes and land around Grenfell. The local residents and those at the scene of the fire will now need long-term monitoring for a host of potential medical problems, from breathing difficulties and skin complaints to cancer and immune system disorders. As the scientists note in their study, public agencies will need to be better prepared to give the public reliable guidance in the event of another such tragedy.