Conference Reports DIOXIN '93

Conference Reports

Dioxin '93

- 1 3 t h I n t e r n a t i o n a l S y m p o s i u m o n C h l o r i n a t e d D i o x i n s a n d R e l a t e d C o m p o u n d s

V i e n n a , A u s t r i a , S e p t e m b e r 2 0 - 2 4 , 1 9 9 3

T o x i c o l o g i c a l A s p e c t s

The most important results of the conference from the toxicological viewpoint can be summarized as follows:

1) PCDD/PCDF levels in human milk and blood in Germany showed a slow decrease in the last years.

2) Humans seem to be less susceptible to the immunotoxic action of PCDD/PCDF than previously assumed.

3) The health hazard of PCB cannot yet be assessed. 4) The nuclear transcription factors c-jun and c-fos bind to the nu-

clear Ah receptor complex.

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From 1987 to 1992 mean PCDD/PCDF levels in human milk in Northrhine Westfalia, Germany, showed a decrease from 32.5 pg I-TEQ/g to 20.5 pg I -TEQ/g milk fat. This decline is associated with a decrease in PCDD/PCDF intake of babies from 163 pg/kg to 99 pg/kg bw day in 1992 on the basis of the following assumptions: - daily intake of 800 mL milk - fat content of 3 % - body weight of 5 kg. Current German background concentrations in blood indicate a parallel decrease from a mean value of 40.8 pg I-TEQ/g blood lipids in 1989 to 26 pg I -TEQ/g blood lipids in 1992 (n = 44). However, it is not clear whether the observed effects are due to the various efforts to reduce PCDD/PCDF emissions in Germany.

First results on the effects of dioxin on human lymphocyte mar- kers in peripheral blood do not provide evidence that mod- erately increased PCDD/PCDF body burdens in adults induce decreases in the cellular components of the human immune sys- tem. These findings indicate that man is certainly less sus- ceptible to the immunotoxic action of PCDD/PCDF than mar- moset monkeys (Callithrix jacchus).

PCB show a broad spectrum of biochemical and toxicological responses. The coplanar, mono-ortho coplanar and di-ortho- substituted congeners act at least in part dioxin-like. Because of insufficient information on the toxic action of individual congeners, it is still impossible to assess the health hazards associated with the intake of PCB. It is necessary to achieve an international agreement on the applicability of the TEF ap- proach to PCB and on individual TEF values.

The nuclear Ah receptor complex interacts with other nuclear transcriptional factors, e.g. c-jun and c-los. These nuclear protein-protein complexes modulate gene expression. The de- tection of these interactions possibly provides the molecular basis for the understanding of the interference of dioxin ac- tion with some endogenous hormone systems.

Peter CIKR YT Hessische Landesanstalt fiir Umwelt, Wiesbaden, Germany

H u m a n E x p o s u r e ( B a c k g r o u n d Exposure)

Humans may become contaminated with polychlorinated dibenzo- dioxins (PCDD) and dibenzofurans (PCDF) through either

- occupational exposure - accidental exposure or - background exposure.

While specimens from humans who have been occupationally or acci- dentally exposed are generally dominated by those PCDD/PCDF con- geners which are characteristic of the respective source or process, samples of humans being exposed through background contamina- tion show a more unique pattern. Human exposure through back- ground contamination is possible by several routes:

- food consumption - inhalation of air and ingestion of particulates from air - ingestion of contaminated soil - dermal adsorption.

The share of each route to the daily intake differs considerably due to the physico-chemical properties of PCDD/PCDF. Estimation of human PCDD/PCDF intake performed by application of pharmaco- kinetic models and by calculation using analytical data for the matri- ces in question resulted in average daily intake values through back- ground contamination of 1 - 3 pg I-TEQ (NATO/CCMS)/kg body weight. This value was estimated for industrialized countries. The average daily PCDD/PCDF intake in developing countries is lower as was shown by PCDD/PCDF analyses of respective human samples.

Usually more than 90 % of the daily PCDD/PCDF intake derives from food. In contrast, exposure via other routes normally contri- butes to less than 10 %. Frequent consumption of foodstuffs from contaminated areas may lead to higher intake levels and subsequently result in an elevated body burden. An example are residents from Scan- dinavia with high fish consumption from the Baltic Proper and for humans with high consumption of eggs from foraging chicken kept in contaminated areas.

The PCDD/PCDF situation in breast milk is still a matter of concern. Analytical data from breast milk samples of various countries show a very similar pattern. However, in contrast to developing countries, the levels in industrialized countries are significantly higher. Thus, to a certain extent PCDD/PCDF levels in breast milk seem to reflect the degree of industrialization of the country where the mother lives. The average daily PCDD/PCDF intake for a breast fed infant amounts to approximately 100 pg I-TEQ (NATO/CCMS)/kg body weight, which exceeds the average daily intake for adults by a factor of al- most 50. Breast milk analyses of the past three years show a tendency to lower levels. A similar declining trend was reported for blood sam- ples from adults with no known exposure living in Germany. These findings could indicate that efforts to reduce emissions are beginning to have beneficial effects on the body burden of humans.

Peter FORST Chemisches Landesuntersuchungsamt, Miinster, Germany

ESPR-Environ. Sci. & Pollut. Res. 1 (1) 59-62 (1994) 59 �9 ecomed publishers, D-86899 Landsberg, Germany

DIOXIN '93 Conference Reports

PCDD/PCDF in Terrestrial Ecosystems

Dioxin '93 produced some new and interesting results concerning the environmental levels and fate of PCDD/PCDF in terrestrial ecosys- tems.

In a plenary lecture HAGENMAIER showed that approximately two thirds of the environmental inventory of PCDD/PCDF in southwest Germany is present in forest soils, indicating that atmospheric depo- sition to forest ecosystems is a key factor in the environmental fate of these compounds. However, the discussion showed that there is as yet no consensus as to how this deposition is occurring. Further- more, HAGENMAIER'S estimates of airborne emissions of PCDD/ PCDF in this region since 1950 accounted for less than 10 % of the PCDD/PCDF present in forest and agricutural soils.

The growing recognition of the importance of aerial transport was reflected in a large number of contributions dealing with air levels of PCDD/PCDF. Ambient air data from England and Japan were pre- sented that showed the same seasonal trend previously reported for Germany, namely a significant increase during the winter months. First data on the particle size distribution of PCDD/PCDF from To- WAI~ showed that 90 % of the particle-botmd PCDD/PCDF are pre- sent on particles with aerodynamic diameter < 1.35 am. KAPPE re- ported on initial efforts to use air mass trajectories to interpret am- bient air data collected in Sweden. Preliminary evidence was presen- ted by LIEBL suggesting that air levels in Germany may be decreasing.

Many groups are measuring PCDD/PCDF in dust deposition gauges and exploring the interpretive possibilities of these data. HIESTER, for instance, found the same seasonal trend in dust deposition measure- ments in Germany that had been observed for ambient air concen- trations. JONES presented simultaneous dust deposition and ambient air data for a number of substance groups and cautioned about the representativeness of the dust gauge data, noting that the deposition of PAll was iust five times higher than that for PCB although the concentrations of particle-bound PAH in the air was 100 times higher.

There was a record number of contributions dealing with plant up- take of PCDD/PCDF. Several groups presented results dealing with root uptake and translocation that confirmed the now widely accep- ted view that this pathway of PCDD/PCDF to aerial plant parts is insignificant. The generality of this conclusion was, however, promptly refuted by HOLSTER, who dearly showed that zucchini and pump- kin plants translocate PCDD/PCDF from the soil to the fruit. ECKER reported a similar behavior for hexachlorobenzene. A few papers fo- cussed more on aerial deposition , and a causal relationship between the gas phase and plant concentrations of CL4-C16DD/F was demon- strated for the first time by WELSCH-PAUSCH.

The potential importance of soil-air exchange of PCDD/PCDF was mentioned by several authors. In an interesting study ALCOCK showed that archived soil samples with low PCB levels accumulated PCB from the air under laboratory conditions, whereas soils from the 1960s with high levels released these compounds. More study is certainly need- ed in this area.

Several groups reported on contaminated environments where indus- trial activity had led to soil contaminations in the middle to high/~g TEQ/kg range. Particularly noteworthy in this regard were a site in Russia, one in the former East Germany, and a former wood treat- ing facility in Finland.

Michael McLACHLAN University of Bayreuth, Chair of Ecological Chemistry and Geochemistry, Bayreuth, Germany

Sources of Dioxins and Furans

After almost twenty years of research on sources and formation of PCDD/PCDF it can be summarized:

- Dioxins and furans have never been produced for any industrial use and are of no benefit.

- Dioxins are the result of anthropogenic activities and are formed as trace contaminants in a variety of industrial processes (e.g. chem- ical industry, pulp and paper industry) and thermal processes.

- Besides the large stationary sources, such as municipal and haz- ardous waste incinerators, dioxins have also been identified as by-products in natural combustion processes such as forest fires or volcanic eruptions.

- In the presence of chlorinated precursos, such as chlorophenols, PCDD/PCDF can be the result of enzymatic activities. This pos- sibility of a biogenic formation was shown in sewage sludge and compost. Results from several research groups showed that there was an overall increase of the dioxin content in sewage sludge and compost. Thus, the production rate of dioxins seem to be more effective than the capability of the same organisms to biodegrade chlorinated hydrocarbons. This finding may be important if in industrial applications bioremediation will be performed on sites with organochlorine contamination.

Whereas in the past the chemical industry and the pulp and paper industry were responsible for environmental contaminations with dio- xins, present input of PCDD/PCDF occurs mainly via combustion processes. Most information about concentrations and amounts of emissions are available from municipal waste incinerators. Due to le- gal requirements - most industrialized countries have emission lim- its for PCDD/PCDF (Austria, Germany, The Netherlands, and Swe- den: 0.1 ng T E Q / m 3, USA: 30 ng ~ P C D D / P C D F / m 3) - this source will be insignificant in the mid 1990s.

During DIOXIN '93 results of emission measurements from sinter- ing plants have been presented which indicate that dioxins from these facilities have been underestimated so far. Presently, in Europe there are about 40 sintering plants which emit between 3 and 10 ng T E Q / m 3 (one plant was found to have an average emission of 47 ng T E Q / m 3 - range 24 - 67.5 ng TEQ/m3). Furthermore, the exhaust stack volume flow can be more than 1 million m 3 per hour. For a single sintering plant in Germany, an annual emission of 250 g TEQ was calculated which is more than the amount presently emitted from the 49 municipal solid waste incinerators.

In the past it was thought that home heating in small ovens and au- tomobile emissions are important sources, especially to explain the peak of dioxin concentrations in air in winter time. Results from sin- gle ovens presented in Vienna showed that burning of untreated wood only gave minor dioxin emissions. When wood treated with chemi- cals or waste wood was fired, higher emission levels could be found, which may lead locally to higher ambient air concentrations. For Switz- erland an annual load of 3 - 10 g TEQ (representing 3 - 10 % of the total emissions) was calculated. A Danish study on the contribu- tion of wood combustion concluded that about 0.4 g N-TEQ/yr. were due to wood-stoves which is roughly 100times lower than the emis- sions from all Danish incinerators.

We have quite a clear mass balance on the occurrence of dioxins in the German pulp and paper industry, which exclusively uses the sul- rite process. Dioxin concentrations both in pulp and paper products have decreased over the years. Papers and paperboards produced from primary fibres have dioxin concentrations in the range from 0.12 to 1.65 ng I-TEQ/kg, whereas products with high amounts of recyc- ling fibres showed higher contaminations (0.83 - 11.53 ng I-TEQ/kg). Pentachlorophenol is still present in wastepaper and can be transferred to recycling paper products (note: in a recent PCP- sample 3 374/~g I-TEQ/kg were detected). Annually between 0.6 to 1.3 g I-TEQ are imported to Germany via 3 million tons of kraft pulp.

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Conference Reports DIOXIN '93

Results by HORSTMANN et al. identified waste water from washing machines as a major source of PCDD/PCDF in sewage sludge. It was shown that the contamination originated in laundry and that PCDD/PCDF accumulate in the dothing during wearing. Further find- ings indicated that textile production and finishing do not produce significant amounts of dioxins. In contrast to PCDD/PCDF, which have never been produced inten- tionally, PCB have been industrially manufactured and used in large quantities. However, less is known about environmental levels and occurrence of PCB. A second source of PCB are thermal processes where PCB are formed as thermodynamically stable products. In a Dutch investigation it was shown that chemical and municipal waste incinerators as well as sintering plants emit coplanar PCB (PCB 77, 126, 160) in the ng/m3-range. Compared with the dioxin concen- trations in the flue gas of these high temperature processes, the co- planar PCB account only for 3 - 10.4 % of the total toxic equivalent (TEF according to I-TEF and PCB TEF proposed by SAVE). Sediment and soil samples contain coplanar PCB with a different pattern in com- parison to the emissions of the thermal processes: 3,3' ,4,4'-TetraCB = PCB 77 was found to dominate in these samples.

Heidelore FIEDLER University of Bayreutb, Chair of Ecological Chemistry and Geochemistry, Bayreutb, Germany

B i o d e g r a d a t i o n o f H a l o g e n a t e d O r g a n i c P o l l u t a n t s

The white rot fungi which can degrade lignin in wood have been shown to be able to degrade a wide range of otherwise very recalcitrant en- vironmental pollutants. The fungi use a variety of mechanisms to min- eralize these chemicals. ExtraceIIular mechanisms exist to detoxify toxic chemicals such that resistance to toxicity is provided. Mecha- nisms are also provided to oxidize already highly oxidized chemicals such as TNT and other nitro explosives. DDT, and other highly chlo- rinated compounds, chlorinated phenols such as pentachlorophenol, cyanides, including metalocyanides, and complex hydrocarbons such as polycyclic aromatic hydrocarbons, such as coal tar, creosote, and anthracene oils.

A cell surface reduction potential is used to reduce some highly oxi- dized compounds such as the nitro-explosives. The reduced products are then susceptible to oxidation by extracellular peroxidases. Phe- nol methyl transferases are capable to reducing chlorophenols, such as pentachlorophenol, for subsequent oxidation by the peroxidases.

The extracellular peroxidases, presently called lignin peroxidases, can catalyze either oxidations or reductions. Oxidation can be either di- rect or indirect. The fungi secrete hydrogen peroxide to oxidize the peroxidases. These oxidized enzymes can then oxidize various envi- ronmental pollutants such as PAH, cyanide, etc.. Indirect oxidation of other pollutants results from mediators which are first oxidized by the enzymes. These include manganese and veratryl alcohol. Ver- atryl alcohol is produced by the fungi and serves as a free radical me- diator. Its one-electron oxidation product, the cation radical, then oxidizes certain chemicals. The fungus also produces oxalate, which will react with the veratryl alcohol cation radical to produce the an- ion radical of oxalate. The oxalate anion radical is an excellent re- ductant. It can, for example, reductively dechlorinate chemicals like carbon tetrachloride. The oxalate anion radical can also reduce mo- lecular oxygen to superoxide. In a protic situation (solvent, environ- ment) superoxide can react with various environmental pollutants. Alternatively, superoxide can reduce iron which will react with hy- drogen peroxide to generate a very powerful oxidant, the hydroxyl radical.

In summary, white rot fungi have many mechanisms to degrade en- vironmental pollutants. Several mechanisms exist each for reductions or oxidations. Thus, complex molecules, such as DDT, can be meta- bolized, similarly as lignin in wood, all the way to carbon dioxide. But the mechanisms are complex. They involve many factors. The complexity of the system means that it may be difficult to apply, but it gives the fungi unique capabilities. Implementing the fungi in bio- remediation systems requires its understanding. Then in situ as well as ex situ bioremediation systems can be engineered for many differ- ent pollutants, including complex, toxic mixtures in various matrices.

StevenD. AUST Biotechnology C e n ~ Utah State Unive~ity, Logan UT, USA

H a l o a c e t a t e s

A half-day session was included to address the environmental and ecotoxicological relevance of short-chain aliphatic halocarbons (SCAH), another example of an involuntary environmental burden of unexpected pollutants of considerable phytotoxicity, i.e. the ha- loacetates. Since most SCAH are anthropogenic and well detectable at trace levels, several of them serve as environmental benchmark chem- icals. The actual contribution of airborne SCAH to dioxin pollu- tion by combustion processes is not yet quantifiable, but it is con- ceivable that they serve as chlorine source for de-novo formation of the former.

The main themes of the half-day meeting were the sources of SCAH, their environmental levels, fate and ecotoxicological relevance; al- though the latter is not easy to assess, such a collective view is of im- portance to develop priority-setting procedures and to determine at which levels the various compounds may elicit health risks and eco- logical disturbances.

The compound classes covered in the various contributions were mainly C2-chlorocarbons , but lower and higher homologs were also addressed to some extent. The series comprised an introductory over- view (H. FRA~X, Tfibingen) emphasizing the characteristic chemical, environmental and toxicological properties of the main C t- and C2-halocarbons including the chlorofluorocarbons. The uptake and effects of these compounds upon plants have been investigated in more detail, as forest trees constitute more than 90 percent of the global biomass. In this context, not only the SCAH as such were taken into account, but also the various haloacetic acids, probable atmospheric degradation products of the former. These have been shown to wide- ly occur in Central and Northern Europe, in all environmental com- partments including plant biomass. Their strong phytotoxicity is il- lustrated by the fact that some of them have been or are still in use as herbicides, such as trichloro- and monochloroacetic acid and de- rivatives thereof. MCA, one of the strongest algal toxicant known, has been shown to occur in needle and leaf samples collected from various locations in Central Europe and Finland at levels between 10 and 100 ppb, similar to its toxicity threshold (EC10) in algal mul- tiplication tests.

P. MtDGLEY (Leinfelden) reported upon the annual production and release of chlorofluorocarbons and 1,1,1-trichloroethane; the pro- duction rates of the former declined in 1992 to about half of their production in the reference year of 1986; and in the case of methyl chloroform the production in 1991 was lower by about 15 % rela- tive to the peak production in 1990 (about 730,000 metric tons). The data on the sales and emissions of the long-living chlorinated solvents methylene chloride, perchloroethane and trichloroethene are less clearcut but seem to indicate declining rates as well.

C. ZETZSCH (Hannover) addressed the atmospheric chlorine radical- dependent photooxidation of perchloroethene; estimations of chlo-

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DIOXIN '93 Conference Reports

rine radical concentrations and rate constants suggest that about 50 % of airborne tetrachloroethene is converted to trichloroacetyl chloride which may either be taken up as such by terrestrial vegetation or by aerosols, where they are hydrolyzed and rained out as trichloroace- tic acid.

P. ScrmODeR (Garmisch-Partenkirchen) presented an overview of stud- ies conducted on plant uptake of SCAH, in particular of tri- and tetrachloroethene, their effects on xenobiotic-metabolizing enzymes induding the glutathione S-transferases, and the effects on photosyn- thesis, respiration, and transpiration as well as a photosynthetic pig- ment patterns. Clear injurious effects could be seen at levels of 25 ppbv, but it should be remembered that atmospheric levels in ru- ral atmosphere are usually 50 to 110fold lower, indicating that di- rect phytotoxicity of chlorocarbons is probably less relevant than the impact of secondary pollutants such as haloacetates.

The fact that there is a widerspread occurrence of trichloroacetate was supported by the data presented by S. JUUTI (Kuopio, Finland), finding trichloroacetate levels in conifer needles from Central and Northern Finland in the range of 20 - 100 ppb; similar levels were reported by J. PLOMACHER (Berlin) for conifer needles from Germany.

The effects of some SCAH (chloroform, trichloroethene, tetrachloro- ethene, trichloroacetate) on soil invertebrates were reviewed by M. ROTH (Ulm). At the levels as typical for non-contaminated soil air, no direct effects are observed on population densities and diversity of the invertebrate coenosis of forest soils. However, model experi- ments at about thousandfold higher concentrations (ca. 30 mg/m 3 soil air), as they may occur upon industrial spills, entail significant decreases in the population densities of nematodes and enchytraeids.

As it is known that SCAH are only slowly degraded by biotic oxida- five processes, reductive pathways are of considerable importance for elimination of these compounds. H. SCHOLZ-MURAMATSU (Stuttgart) presented and summarized the data of own investigations and of other groups on rates and pathways of reductive dehalogenation, no- tably of tri- and tetrachloroethene, and dicussed the possibility to utilize reductive microbial metabolism for clean-up of SCAH-polluted waste waters by combining an anaerobic stage before the aerobic activated sludge stage.

In the concluding lecture, E. EDER (Wfirzburg) presented an abridg- ed, nevertheless instructive overview of the main pathways of me- tabolic elimination and activation of SCAH, their potential acute and chronic toxicity, and especially their carcinogenicity. Vinylchlo- ride and 1,2-dichloroethane are known to be the most relevant in this

respect. Although there are few actual measurements of their atmo- spheric levels in urban atmosphere, it may be anticipated that 1,2-dichloroethane with its relatively short lifetime of less than a day does not constitute an excess risk in human carcinogenicity, also be- cause being phased out as scavenger together with leaded petrol. Ex- posures at the work place to the typical halocarbon solvents exceed those in the open environment by factors of 104 to 103 (up to seve- ral hundred mg/m3); under these conditions, the fact that many chlo- rocarbons are suspected weak carcinogens may be of relevance al- though most epidemiological studies on occupational exposure do not show a significant increase of most cancer types,

The clear message from a collective view of the lecture series was the fact that (1) ecotoxicilogical properties cannot be drawn from mam- malian toxicological studies or human epidemiological investigations, (2) less advanced organisms including primary producers and decom- posers are often more susceptible to the impact of xenobiotics than humans.

The fact that in the open environment abiotic atmospheric oxidations may give rise to toxic secondary products could be gleaned from sev- eral lectures; the whole sequence led the interested auditorium across a number of aspects and facts which are important in ecotoxi- cological risk assessment. As the short section did allow to only cover a few relevant topics and mechanisms governing environmen- tal behavior and ecotoxicological properties of SCAH, it is planned to include them again in expanded form at the next Dioxin-Conference in Kyoto/Japan 1994.

Hartmut FRANK Institute of Toxicology Universitdt of Tiibingen, Germany

Announcement:

DIOXIN '94 will be held in Kyoto, Japan, November 21 - 25, 1994 For further information please contact: DIOXIN '94 - Symposium Secretariat, Congress Corporation Kinki Invention Center Bldg. 14 Yoshida Kawahara-cho, Sakyo-ku Kyoto / Japan Phone: + 81-75-752-0888 Fax: + 81-75-752-2963

Dioxin '93 Publication

Short papers of all oral presentations and posters presented at the Dioxin '93 Conference in Vienna are available in four volumes. They are published as volumes 11 to 14 of the series "Organohalogen Compounds". Dioxin '93 short papers are sold only as set of four volumes.

Price of the set: 1,200 Austrian Shillings (plus postage)/DM 180,00/US $110.00 (postage induded). The volumes can be purchased from either:

Austrian Federal Environmental Agency Mr. A. Riss Spittelauer L~nde 5 A-1090 Vienna, Austria Phone: +43-1-31 30 43 06 Fax: +43-1-31 30 44 00

Payment (payable to Umweltbundesamt Wien) by cheque, bank draft or direct bank transfer to PSK Wien, account no. 5 60 00 03

o r :

Ecoinforma Dr. H. FIEDLER Jean-Paul-Strafle 30 D-95444 Bayreuth, Germany Phone: + 49-9 21 55 21 54 Fax: + 49-9 21-5 46 26

Payment (payable to Verein Umwelt) by cheque, bank draft or di- rect transfer to Bayerische Vereinsbank, Bayreuth, BLZ: 77 32 00 72, account no. 3 23 89 54

62 ESPR-Environ. Sci. & Pollut. Res. 1 (1) 1994