Dioxins & Furans

On this page (7 sections)

1. What Elm Dirt does about dioxins
2. What it is
3. Where it comes from
4. Why it matters
5. What the research shows about microbes in our products
6. What to expect
7. Studies

What Elm Dirt does about dioxins

A dioxin site gets two treatments running together. Living biologicals and compost build a large, active soil population that includes organisms peer-reviewed research shows can attack the dibenzofuran and dibenzo-p-dioxin ring. Carbon goes in alongside them to hold what the biology doesn’t reach: in published work, biochar and activated carbon added to dioxin-contaminated soil cut the measured availability of total dioxins and furans by 40 to 92 percent, confirmed by earthworm uptake [1]. The dioxins stay in the soil but move far less readily into plants, animals and people.

We work directly with applicators and can be on site to plan, apply and sample. An independent lab measures totals and bioavailability together, since binding never shows up as a lower total. Expect months to a year or more.

What it is

“Dioxins” is shorthand for two related families, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. About 419 dioxin-related compounds have been identified, and roughly 30 have significant toxicity. The most toxic, 2,3,7,8-TCDD, is classified by the International Agency for Research on Cancer as a known human carcinogen [2].

How many chlorine atoms a molecule carries, and where they sit, sets both its toxicity and how hard it is to break down.

Where it comes from

Almost nobody makes dioxins on purpose; they form as by-products when chlorine and organic material burn or react together at high temperature:

• uncontrolled burning of waste, especially plastics and treated material
• smelting, chlorine bleaching, and chemical and pesticide manufacturing
• derailments and chemical fires where chlorinated cargo burns
• backyard burn barrels, a bigger source in rural areas than most people expect
• volcanoes and forest fires

After a release, dioxins settle out of smoke onto soil and surfaces and stay there. They bind tightly to soil organic matter, barely dissolve in water, and hold up against sunlight and most microbes. Food accounts for more than 90 percent of human exposure, mainly meat, dairy, fish and shellfish, which is the route from contaminated soil into the food chain [2].

Why it matters

Dioxins build up in the body, with an estimated human half-life of 7 to 11 years [2]. Short-term high exposure is linked to skin lesions and altered liver function. Long-term exposure affects the immune system, the developing nervous system, the endocrine system and reproduction.

On the ground, the problem for a landowner or municipality is that dioxin-bearing soil travels as dust and as eroded sediment.

What the research shows about microbes in our products

Independent lab analysis (Biome Makers) identified these organisms in Elm Dirt products, and peer-reviewed research shows each can act on the dioxin and furan ring.

• Comamonas testosteroni and related Comamonas strains grow on dibenzofuran as their only carbon source, and one opens the ring by angular dioxygenation at the 4,4a position [3], the same attack the dedicated dioxin specialists use. This group’s biphenyl dioxygenase also oxygenates both dibenzofuran and dibenzo-p-dioxin [4].
• Pseudomonas putida strain B6-2, grown on biphenyl, breaks down dibenzofuran, the unchlorinated parent compound. Its genome has been mapped for mineralizing PAHs and dioxin-like heterocycles [5][6].
• Terrabacter sp. carries the dibenzofuran 4,4a-dioxygenase genes and mineralizes the compound [7].

A published review of the field reports aerobic microbial degradation mainly for the lower-chlorinated congeners, with work going back to the early 1990s and including soil studies as well as flask work [8]. Whether that happens on a particular site gets tested on that site.

What to expect

Heavily chlorinated congeners resist biology, because each added chlorine makes the ring harder to attack, and 2,3,7,8-TCDD, the most toxic congener, is among the toughest [8]. The carbon half of the plan is there for these.

Standard total-concentration methods extract bound and unbound contamination alike, so even successful binding leaves the totals report unchanged. That is why bioavailability tests run alongside the totals, both by an independent lab.

Dioxin work takes months to a year or more, checked by independent lab testing, and a one-season promise on dioxins should raise questions.

Our soil-restoration pilot in East Palestine, Ohio uses this design.

Studies

1. Chai Y, et al. (2012). Effectiveness of activated carbon and biochar in reducing the availability of polychlorinated dibenzo-p-dioxins/dibenzofurans in soils. Environmental Science & Technology 46(2):1035–1043. doi:10.1021/es2029697
2. World Health Organization. Dioxins and their effects on human health. who.int fact sheet
3. Wang Y, Yamazoe A, Suzuki S, Liu CT, et al. (2004). Isolation and characterization of dibenzofuran-degrading Comamonas sp. strains isolated from white clover roots. Current Microbiology 49(4):288–294. doi:10.1007/s00284-004-4348-x
4. L’Abbée JB, Barriault D, Sylvestre M (2005). Metabolism of dibenzofuran and dibenzo-p-dioxin by the biphenyl dioxygenase of Burkholderia xenovorans LB400 and Comamonas testosteroni B-356. Applied Microbiology and Biotechnology 67(4):506–514. doi:10.1007/s00253-004-1791-3
5. Li Q, et al. (2009). New metabolites in dibenzofuran cometabolic degradation by a biphenyl-cultivated Pseudomonas putida strain B6-2. Environmental Science & Technology 43(22):8635–8642. doi:10.1021/es901991d
6. Wang W, et al. (2021). Genetic mapping of highly versatile and solvent-tolerant Pseudomonas putida B6-2 (ATCC BAA-2545) for mineralization of PAHs and dioxin-like compounds. Environmental Microbiology 23(8):4309–4325. doi:10.1111/1462-2920.15613
7. Kasuga K, et al. (2013). Cloning of dfdA genes from Terrabacter sp. strain DBF63 encoding dibenzofuran 4,4a-dioxygenase and heterologous expression in Streptomyces lividans. Applied Microbiology and Biotechnology 97(10):4485–4498. doi:10.1007/s00253-012-4565-3
8. Field JA, Sierra-Alvarez R (2008). Microbial degradation of chlorinated dioxins. Chemosphere 71(6):1005–1018. doi:10.1016/j.chemosphere.2007.10.039