Substance and perceptions of environmental impacts of dioxin emissions P. Deriziotis* and N.J. Themelis Earth Engineering Center, Columbia University Work sponsored by the Waste-to-Energy Research and Technology Council. *2002 Scholar SWP-ASME
Order of presentation: 1. What are dioxins, environmental transport in air, water and soil. 2. Bioaccumulation, human exposure, reported heath effects. 3. Pre-MACT and Post-MACT emissions of U.S. WTEs. 4. Pre-MACT studies of dioxin concentrations near Waste-to-Energy plants. 5. Conclusions.
Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans: Collectively known as dioxins (PCDD/PCDF) planar, tricyclic ethers with up to eight chlorine atoms attached on carbon atoms 1 to 4, and 6 to 9. include 210 congeners: 75 polychlorinated dibenzo-p-dioxins (PCDD) 135 polychlorinated dibenzofurans (PCDF)
Dioxins (2,3,7,8 TCDD) Furans (2,3,7,8 TCDF)
Formation in combustion processes Formation Temperatures PCDD: 200 to 400 C (or on gas cooling 400 to 200 C) PCDF: 500 to 800 C (or on gas cooling 800 to 500 C) HCl is catalytically (Cu) converted to Cl 2 gas-phase D/F chlorination 4 HCl + O 2 2 Cl 2 + 2 H 2 O Direct Chlorination of aromatic molecules (Ar) by CuCl 2 - ArH + CuCl 2 ArHCl + CuCl - ArHCl + CuCl 2 ArCl + CuCl + HCl
Physical and Chemical Properties of Dioxins High melting point - above 593 K Low vapor pressure - below 10-6 Pa Low water solubility Easily bound to solid particles: soil, colloids and organic matter.
Environmental Transport Dioxins can be found in all environmental compartments (air, water, soil, organisms). Sediments are the final environmental sink for all PCDD/PCDF releases.
Dioxins in the atmosphere PCDD/PCDF enter the atmosphere in the form of vapor (sublimation)or bound to fine solid particles (PM). The vapor-to-particle ratio depends on the vapor and suspended particle concentrations. Vapor emissions are easily degraded by sunlight (photolysis) and reaction with hydroxyl (OH - ) radicals.
Dioxins in the atmosphere (cont.) Once dioxins become associated with particles, their rate of degradation is reduced to very low levels. The rate of degradation is higher for the less chlorinated compounds. Dioxins that attach to particles precipitate from the atmosphere by wet or dry deposition.
Fate of dioxins deposited on land: The persistence of toxic TCDD on top soil surfaces may vary from less than one year to three years. Half-lives in soil interiors may be as long as 12 years. Re-suspension of soils (dust, wind) poses the threat of inhalation and increase of the contaminated area.
Fate of dioxins deposited on water: PCDD/PCDFs deposited on water from the atmosphere, follow four routes: Degrade by photolysis or biodegradation Adsorb into sediments Bioaccumulate into organic matter. Revolatilize (very low rates)
Fate of dioxins deposited on water (cont.): The fate and residence time of dioxins in water are closely related to the particles on which they are deposited. PCDD/PCDFs bind strongly to dissolved (TOC) or particulate organic matter.
Fate of dioxins deposited on water (cont.): Particles deposited in deep waters (minimal turbulence), become incorporated into the sediment and are immobilized. PCDD/PCDFs are very stable when incorporated into sediments. Low levels of dioxins have been detected in 8000-year-old marine sediments.
Bioaccumulation on land The food ingested by farm animals includes up to 7% by weight of soil. Contaminated soil can enter the food chain by plant and vegetable consumption by meat and dairy consumption Dioxins are lipophilic and concentrate in foods that contain animal fat such as beef, pork, poultry, fish, dairy products and eggs.
Bioaccumulation in water Bioaccumulation in sea organisms: Ingestion of sediments Direct uptake from water through the gill membranes. Dioxin concentrations in these organisms is directly related to the sediment concentrations.
Toxicity The compound 2,3,7,8-TCDD, is considered to be the most toxic man-made substance. Laboratory tests have shown that the lethal dose of 2,3,7,8-TCDD, varies by more than 5000-fold between the most sensitive and the least sensitive species.
Converting grams of total dioxins to grams TEQ: The World Health Organization has established toxic equivalence factors (TEF) representing the toxicity of each compound on a scale of 0 to 1 (TEF of 2,3,7,8-TCDD =1). Using these factors, and the measured distribution of the various D/F in the WTE process gases, EPA has established that the prevailing ratio of Total to Toxic dioxins is approximately 50. Therefore, 50 grams of total D/F emissions (as measured by WTE plants) correspond to 1 gram of toxic equivalent (TEQ).
Human Exposure Inhalation small exposure pathway, mainly because of the low concentration of dioxins in the air and the absence of an accumulating mechanism. Dermal Absorption Slow, does not contribute significantly to human exposure.
Human Exposure The important pathways of human exposure are ingestion of fat-containing food. Ingestion of contaminated matter results in the absorption of 30% to nearly 100% of the contained dioxins. Studies have concluded that populations living in areas with higher dioxin concentration are not affected, if they do not consume locally produced foods.
Effects on human health? In studies with rats exposed at levels 100 to 1000 times higher than present background levels, different types of carcinomas were observed. On the basis of such studies, dioxin contamination is assumed to be associated with carcinogenic, reproductive, developmental and immunologic effects on humans, although there has not been sufficient evidence to establish a direct link.
Effects on human health? (cont.) Carcinogenic Effects Bertazzi et al reported lower rates of cancer occurrence in the Seveso region after the 1976 accident. the International Agency for Research on Cancer (IARC) concluded that there was inadequate evidence of the carcinogenicity of PCDD compounds, other than TCDD in humans. EPA currently accepts a causal relationship between TCDD exposure and cancer risk.
Effects on human health? Effects on Reproduction Animal studies after exposure in high doses of dioxins indicated teratogenic effects and several structural and reproductive defects including increased fetal mortality, increased fetal resorptions, decreased litter size, and reduced body weight of offspring. Studies in human population were unable to detect any increase in specific birth defects.
Effects on human health? Genetic Effects Animal studies produced contradictory results regarding genetic alterations such as DNA damage, gene mutations, sister chromatid exchange and cell transformation. Human studies concluded that effects of dioxins on genetic material are not observed.
Tolerable Daily Intake (TDI) for humans The high uncertainty in the scientific and medical community about assessing dioxin health risks for the general public is reflected in the different TDI levels imposed by regulatory agencies around the world: Health Canada (1996): 10 picograms (10-12 gram) TEQ/kg of body weight/day Japan s Ministerial Council on Dioxin Policy: 4 pg TEQ/kg World Health Organization: 1-4 pg TEQ/kg European Commission s Health and Consumer Protection Directorate: 2 pg TEQ/kg US Agency for Toxic Substances & Disease Registry: 1 pg TEQ/kg
Tolerable Daily Intake (TDI) for humans in various countries 10 9 TDI - pgteq/kg of body weight/day 8 7 6 5 4 3 2 1 0 US Agency for Toxic Substances & Disease Registry (2000) World Health Organization [Min] (1998) European Commission s Health and Consumer Protection Directorate (2001) Ministerial Council on Dioxin Policy of Japan (1999) World Health Organization [Max] (1998) Health Canada (1996)
Means of Dioxin Reduction in WTEs Good combustion practice to destroy any dioxins in the feed and to minimizase formation on cooling. MACT: Air Pollution Control Devices to remove dioxins formed in cooling of gas (activated carbon injection, fabric filter, etc.).
Post-MACT Implementation (Source: USEPA) 0.1 ng/dscm
1000 100 10 1 0.1 0.01 Effect of MACT (from USEPA data) PreMACT - MACT - EU standard 0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 18000000 Cumulative capacity ton EU Standard Cumulative TEQ Cumulative pre MACT TEQ Cumulative Dioxin TEQ
Enormous reduction of dioxin emissions throughout the U.S. WTE Industry (from USEPA data)
Combustion and Air Control Systems used in the U.S. MB/WW - Mass Burn- Water Wall (Martin, Von Roll, DBA) MB/RC - Mass Burn -Rotary Combustor RDF - Refuse Derived Fuel (including SEMASS) SD - Spray Dryer FF - Fabric Filter CI - Carbon Injection SNCR - Selective Non-Catalytic Reduction ESP - Electrostatic Precipitator DSI - Dry Sorbent Injection
Emission Factors for Various Systems range from 0.1-0.45 grams TEQ per million metric tons of MSW combusted (from USEPA data)
Reduction of dioxin emissions in all sectors 1987 to 2002 (Source: USEPA) Not included: Flaring of landfill gas (35% of total collected): Subject of 2003-2004 WTERT study.
Why the U.S. WTE industry stopped being the center of attraction (from USEPA data)
How the U.S. WTE industry stopped being the center of attraction (from USEPA data)
We have seen in the previous slides that the U.S. WTE industry reduced dioxin emissions since the late eighties by a factor of one hundred. In the following slides we will see what were the impacts of WTE dioxin emissions before the MACT improvements were made.
Results from pre-mact Environmental Monitoring Studies Around Incinerators Reference: Scientific Studies reported in Waste Incineration and Public Health, National Research Council, National Academy Press, 2000
Case Studies USEPA (1991): A detailed study of ambient air quality in vicinity of MSW combustor in Rutland, VT (NB: Rutland VT combusted 240 tons/day of MSW; and was equipped with ESP and wet scrubber). It was concluded that the incinerator was not the primary source of PCDDs and PCDFs in the ambient air surrounding the facility.
Case Studies Hunt, G., B. Maisel, and M. Hoyt: Monitoring of PCDD/PCDFs in the vicinity of the Bridgeport, CT, waste-toenergy facility, 1991. Measurements were taken before and after the plant became operational. The results showed little difference in ambient concentrations.. between the pre-operational phase (0.097 pg/m 3 ) and the post-operational phase (0.088 pg/m 3 ). (How come lower, after?)
Case Studies Stubbs, K.P. Impact of the Greater Vancouver Incinerator Emissions on Regional Soils and Vegetation, 1993. Stubbs (1993) examined trace metals and air quality measures in the vicinity of.the Vancouver incinerator and concluded that startup and operation of of the plant had no measurable effect on air quality.
Case Studies A detailed study of ambient air in the vicinity of a greater Detroit plant that burned refuse derived fuel... evaluated many potential chemicals of concern (PCDDs and PCDFs, ) at four monitoring sites over a period of 2.5 years. One of the monitors was installed at the point of maximal effect, as predicted by air modeling. All statistical procedures showed that there was no observable effect of the facility on the measured concentrations of any of the chemicals studied.
Case Studies Eitzer, B.D, in Chemosphere, study near CT WTE, 640 t/d, plant equipped with spray dryer and fabric filter, 1995. Eitzer (1995) analyzed bovine-milk samples for chlorinated dibenzodioxins and furans from farms near an MSW incinerator in Connecticut and found no statistically significant differences between pre-operational and postoperational concentrations.
Case Studies McLaughlin study of dioxins in the soil near a Hamilton, Ontario, WTE (1989). Incineraator had been in operation for ten years. OCDD was the congener most frequently detected. The range of OCDD was from 1.3-3,500 ppt for the study area and 810-3,200 ppt for the controls.the authors concluded that stack emissions have not accumulated in the vicinity of the plant.
Case Studies: The one U.S. study that showed a negative effect: Lorber (1998) examined PCDD/PCDFs in.soil and air around the Columbus, Ohio, municipal WTE facility. This facility was estimated to emit as much as 1000 g of TEQ per year for..11 years. (NB: as compared to less than15 grams per year in 2000 from all U.S. WTEs). Two air samples downwind of the facility.. had TEQ concentrations... 5-fold higher than background.
CONCLUSIONS: The U.S. post-mact WTE emissions are less than 2% of the national dioxin emissions. When the dioxin emissions of U.S. WTEs were 100 times higher than at present, several scientific studies showed no impact on the region around WTEs, with the noted Columbus exception. The WTERT study on dioxins has not brought forth any report of health effects of dioxins on humans, other than the Seveso 1976 accident and the reports on Agent Orange use in Vietnam war. WTERT would appreciate receiving information on any such report.
CONCLUSIONS: The U.S. post-mact WTE emissions are less than 2% of the national dioxin emissions. When the dioxin emissions of U.S. WTEs were 100 times higher than at present, several scientific studies showed no impact on the region around WTEs, with the noted Columbus exception. The WTERT study on dioxins has not brought forth any report of health effects of dioxins on humans, other than the Seveso 1976 accident and the reports on Agent Orange use in Vietnam war. WTERT would appreciate receiving information on any such report.
Thank you! This PowerPoint presentation will be available at the web page of the Waste-to-Energy Research and Technology Council www.columbia.edu/cu/wtert as of May 5, 2003