The US Chemical Safety Board's latest accident investigation report is a reminder of the importance of tackling static electricity issues around the plant. In Italy, research finds ongoing thyroid problems, 30 years after the Seveso disaster. Sean Ottewell reports.
Afire and series of explosions at the Barton Solvents, Des Moines, Iowa, chemical distribution facility on 29th October 2007 was caused by a static electrical spark resulting from inadequate electrical bonding and grounding during the filling of a portable steel tank, the US Chemical Safety Board (CSB) has determined in its final report.
One employee received minor injuries and one firefighter was treated for a heat-related illness in the accident, which occurred at about 1 pm. A large plume of smoke and rocketing barrels and debris triggered an evacuation of the businesses surrounding the facility.
As the CSB Case Study notes, the main warehouse structure was destroyed and Barton's business was significantly interrupted. The accident occurred about three months after a 17th July explosion and fire destroyed a Barton Solvents facility in Wichita, Kansas. The CSB attributed that accident to static sparks and lack of bonding and grounding as well in a June 2008 final report.
CSB chairman and ceo John Bresland said, "These accidents show the need for companies to address the hazards associated with static electricity and flammable liquid transfer. They should apply good practice guidelines - outlined in our case study - to determine if facilities are properly designed and safety operated."
The accident in Des Moines occurred in the packaging area of the facility as an operator was filling the 300-gallon steel tank, known as a tote, with ethyl acetate, a flammable solvent. The operator had secured the fill nozzle with a steel weight and had just walked across the room when he heard a 'popping' sound and turned to see the tote engulfed in flames. Employees tried unsuccessfully to extinguish the fire with a handheld fire extinguisher before evacuating.
CSB lead investigator Randy McClure said: "The CSB investigation found the nozzle and hose were not intended for use in transferring flammable liquids. Furthermore, we found the steel parts of the plastic fill nozzle and hose assembly were not bonded and grounded. Static electricity likely accumulated on these parts and sparked to the stainless steel tote body, igniting the vapour that accumulated around the opening of the tote during filling."
The report notes that static electricity is generated as liquid flows through pipes, valves, and filters during transfer operations. Metal parts and equipment must be electrically wired to each other, known as bonding, and then electrically connected to the earth, known as grounding.
"In this case, all the conductive metal objects in the nozzle and hose, and the steel weight which was suspended from the handle by a wire, were all isolated from ground and were susceptible to static accumulation and discharge," McClure said. "This is a set-up for disaster."
The packaging area - where the fire started - had no automatic sprinkler system and was adjoined to the flammable storage warehouse. The investigation found the wall separating the two areas was not fire-rated. As a result, the warehouse was rapidly consumed, and although this area had an automatic sprinkler system, it was incapable of extinguishing the large blaze.
The case study lists several key lessons for safe handling and storage of flammables. "We would hope every operator of similar liquid transfer facilities downloads and studies this report and the earlier Barton Solvents Wichita report to avoid a repetition of these accidents," Bresland said.
Facilities are urged to ensure that equipment used to transfer liquids is properly bonded and grounded; fire suppression systems should be installed in packaging areas; and packaging to be used for flammable liquids - such as the portable steel tanks - should be separated from bulk storage areas by fire-rated walls and doors.
The CSB investigation determined that if Barton had implemented a comprehensive static electricity and flammable liquid safety programme, in compliance with current regulatory standards and good practice guidelines, the fire likely would have been prevented.
Seveso problems linger
Three decades after an accident at a chemical factory in Seveso, Italy in 1976, which resulted in exposure of a residential population to the most dangerous type of dioxin, newborn babies born to mothers living in the contaminated area at the time of the accident are over six times more likely to have altered thyroid function than those born to mothers in a non-contaminated area.
The study finding these results is published in the open access journal PLoS Medicine this week by Andrea Baccarelli of the University of Milan and colleagues from the USA and Italy*.
Dioxins are toxic chemicals that are a by-product of waste incineration and which persist in the environment and accumulate in people. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) - the dioxin released by the Seveso disaster - is the most toxic type of dioxin and in 1997 was declared a class-1 carcinogen by the World Health Organisation. Animal studies and some studies in people have shown that maternal exposure to dioxins can damage the function of their babies' thyroid gland.
To investigate the continuing effect of TCDD on children born in the Seveso area, Baccarelli and colleagues investigated three groups of child-bearing women.
These included 1772 women who were living very near the factory in Seveso at the time of the accident (the most contaminated area, Zone A) or the nearby area where contamination was less but still high (Zone B), and the same number of women from the surrounding non-contaminated area (Zone Reference). Altogether these women had 1014 babies between 1994 and 2005.
The researchers measured the amount of thyroid secreting hormone (TSH) in the blood of these children - a common practice at birth in many countries, because high blood TSH levels are associated with a failing thyroid, which can lead to permanent damage to the baby's developing body and brain.
The results show that one long-lasting effect of the Seveso disaster (and potentially of other areas where there have been high environment levels of dioxins) is a deleterious effect on the health of children in the area born decades after the accident. The babies from Zone A - the area most highly contaminated with TCDD after the accident in 1976 - were 6.6 times more likely to have a high blood TSH level than those from the surrounding area that was not contaminated. Those babies born in Zone B had intermediate TSH blood levels.
The researchers also studied 51 pairs of mothers and children for whom dioxin measurements were available at the time of delivery, and found that the blood TSH levels were highest in the babies whose mothers had the highest levels of dioxin in their blood.
As the authors conclude, these findings suggest that maternal exposure to dioxins such as TCDD in the environment produces damaging effects on the thyroid function of their babies "far apart in time from the initial exposure."
Further studies on the long-term progress of the children is needed in order to establish whether this results in longer term development problems, such as reduced growth and intellectual development.