Thallium Source Research Articles

Potential high-risk release sources of thallium and arsenic from surrounding rocks of a typical thallium and arsenic mining area in southwest China

Abundant naturally and anthropogenically exposed surrounding rocks (NESRs and AESRs) in mining areas may pose persistent threats as sources of potentially toxic elements (PTEs), but this has been historically overlooked, especially for thallium (Tl) and arsenic (As). Here, the release risks of Tl and As from both NESRs and AESRs in a typical TlAs sulfide mining area were investigated. In a single leaching process, AESRs released 10.4 % of total Tl (157 μg L−1) and 32.5 % of total As (4089 μg L−1), 2–3 orders of magnitude higher than NESRs. Prolonged multiple leaching tests revealed notable and long-term risks of release of Tl and As from AESRs, associated with oxidation and dissolution of iron/sulfur-bearing minerals. Substantial release of PTEs was linked to the transformation/degradation of the -OH functional group and extensive dissolution of secondary sulfate minerals in AESRs. Ultrafiltration and STEM-EDS indicate that 18.4 % of water-extracted As released from AESRs existed as natural nanoparticles consisting of iron/sulfur-bearing minerals. This study highlights the high risks of Tl and As release from anthropogenically exposed surrounding rocks and the importance of nanoparticles in PTE transport, and provides insights into the control of PTEs in mining areas.

Substance-flow analysis and emission-reduction strategies for thallium in the steel industry process

Thallium, which is a highly toxic and sparsely distributed element, is often found in various mineral compounds. Its release into the environment primarily occurs through the mining of metals, metallurgical processes, and the combustion of fossil fuels. These activities release thallium from minerals, concentrating it in ash, wastewater, and exhaust gases, thus contributing to thallium pollution. With over 600 active steelworks in China continuously producing steel, the risk of thallium pollution is significant and thus presents a major challenge. This research focuses on understanding the mechanisms of the physical phase evolution, migration pathways, and emission characteristics of thallium in steelworks. For the first time, a thallium flow network in steelworks is developed using substance flow analysis. This involves examining the input, output, waste discharge characteristics, and potential for reduction of thallium. The findings reveal that iron concentrate is the primary source of thallium in steelworks, with dust being the main form of thallium output. The quantities of thallium input, output, and circulation are found to be 425.44, 365.49, and 49.66 mg/t-CS, respectively. Implementing source control, endpoint governance, or a combination of both can reduce pollutant emissions in steelworks by 41.47%, 43.35%, and 65.63%, respectively. This study enhances our understanding of thallium pollution in steelworks.

Thalliomelane, TIMn7.54+Cu0.52+O16, a new member of the coronadite group from the preglacial oxidation zone at Zalas, southern Poland

Abstract Thalliomelane, a new member of the coronadite group (hollandite supergroup), was discovered at Zalas near Kraków in southern Poland (the southern margin of the Kraków-Silesia Monocline) in relics of a preglacial supergene mineralization disseminated in a fault breccia in Middle Jurassic sandy limestone. The mineralization formed at the expense of a sulfide assemblage, which was most likely the source of thallium, related to rejuvenation of Early-Paleozoic fault zones in the Sava phase of the Alpine orogeny. Thalliomelane occurs rarely and exclusively in the form of fibrous and highly porous tiny aggregates <50 µm in size that fill small fractures and voids in the sandy limestone host rock. Microprobe analyses based on 16 O and 8 octahedral cations per formula unit resulted in the mean empirical formula [Tl0.77(10)Ba0.21(3)K0.03(1)Na0.01(0)Pb0.01(0)]Σ1.03(7)[Mn7.15(11)4+Cu0.63(4)2+Co0.08(3)2+Fe0.06(3)3+Ni0.03(1)2+Si0.03(2) Mg0.01(1)]Σ8[O15.67(24)(OH)0.33(24)], corresponding to the formula Tl(Mn7.54+Cu0.52+)O16 for the thalliomelane end-member. The mineral crystallizes in the tetragonal system, space group I4/m, and has unit-cell parameters a = 9.8664(12), c = 2.8721(4) Å, V = 279.59(8) Å3, Z = 1. The crystal structure of thalliomelane, measured with 3D electron-diffraction, was refined to an R1 index of 23.74%. Thalliomelane has the hollandite-type structure. The Mn4+ cations, substituted by Cu2+ at an amount of ~0.5 apfu, are octahedrally coordinated by oxygen atoms. Four double chains of edge-sharing (Mn,Cu)-O octahedra share corners with each other to form tunnels along the [001] direction. Tl+ cations are located in the tunnels, occupying partially the origin and center of the unit cell. The formation of thalliomelane was most probably connected to the weathering of a sulfide mineral assemblage under semi-arid to arid climate. It resulted in the release of Tl and other components of the mineralization into water under the influence of Cl-, Br-, and I-bearing brines and pore waters from the Carpathian flysch or from sediments of the Carpathian foredeep mobilized by compaction during the Sava phase. Via the interaction of these waters, the primary ores altered mainly into goethite, cuprite, malachite, Mn oxides of the coronadite type, with subordinate Cu sulfates, Pb arsenates, Bi oxy-chlorides, and traces of iodargyrite. This assemblage indicates oxidation at a progressively increasing pH of ~8–10 and Eh of the order of +0.4–0.5 V. In this setting, thalliomelane could have formed from a cryptomelane-type Mn oxide in contact with Tl-bearing aqueous solutions through Tl-for-K exchange over time.

Temporal sedimentary record of thallium pollution in an urban lake: An emerging thallium pollution source from copper metallurgy.

Thallium (Tl) is an extremely toxic metal with high risk. Sediment samples from a well dated sediment core retrieved from a heavily polluted urban lake were measured to assess the magnitude of Tl pollution and reveal its transfer mechanisms within the lake. The results show that the lake has experienced serious Tl pollution during the past 60 years, owing to a large influx of Tl-bearing wastes mostly from a neighboring copper (Cu) smelter. The Tl contents in the sediment core at different depths generally correlated positively with the production scale of Cu smelting activities in the past. Further mineralogical analysis on the electrostatic precipitator dust from the Cu smelter and highly-polluted samples from the sediment core by electronic microscopy and X-ray diffraction suggested that Tl was primarily bound to quartz and aluminosilicates. Large quantities of Tl were also observed in diatom frustules collected from the sediments, suggesting a potentially significant role of biogenic silicates in the uptake and transfer of Tl in the sediment-water system. The findings indicate a new and emerging pollution source of thallium arising from copper metallurgy activities. The results also highlight the necessity of strengthened monitoring and regulations towards Tl pollution in environmental systems impacted by Cu smelting activities in China and other nations.

Potentially toxic elements in fly ash dependently of applied technology of hard coal combustion.

Coal combustion is one of the most significant anthropogenic sources of thallium in the environment. This study presents the results of determination of thallium and some toxic elements (Pb, Cd, As, Ni, Zn, and Cu) concentration in fly ash produced in the coal combustion in conventional furnaces (pulverized coal furnace and grate furnace), in a fluidized-bed furnace with circulation bed, and in a home furnace. The high content of thallium was determined in ash produced in the grate furnace (on average 10.7mg/kg) and fluidized-bed furnace with circulation bed (6.6mg/kg). The average content of Tl in the fly ash of the pulverized coal furnace and in the home furnace is 1.7 and 2.4mg/kg, respectively. There was a strong relationship between the occurrence of Tl and As, Cd, Pb, Cu, and Zn in ash from grate and pulverized coal furnace.

Examining of Thallium in Cigarette Smokers.

Smoking is one of the sources of thallium which is considered as a toxic heavy metal. The aim of this study was to determine urinary thallium levels and related variables in smokers, compared to a control group. The study was conducted on 56 participants who had smoked continuously during the year before they were referred to Kashan Smoking Cessation Clinic. Fifty-three nonsmokers who were family members or friends of the smokers were selected as the control group. Urinary thallium was measured in both groups (n=109) using atomic absorption spectrophotometry. The mean value (with SD) for urinary thallium in the smokers (10.16±1.82μg/L) was significantly higher than in the control group (2.39±0.63μg/L). There was a significant relationship between smoking duration and urinary thallium levels (P=0.003). In a subgroup of smokers who was addicted to opium and opium residues (n=9), the mean level of thallium (37.5±13.09μg/L) was significantly higher than in the other smokers (4.93±4.45; P=0.001). Multiple regression analysis showed opioid abuse, insomnia, and chronic obstructive pulmonary disease (COPD), together were strong predictors of urinary thallium levels in smokers. There was no significant difference in thallium level in hookah smokers (P=0.299) or in those with COPD compared to other smokers (P=0.375). Urinary thallium levels of smokers with clinical signs of depression, sleep disorders, memory loss, and sweating were higher than those of smokers without these signs. Since thallium, as other toxic metals is accumulated in the body, and cigarette smoking also involves carcinogenic exposures and health hazards for passively exposed people, the need for cigarette control policies is emphasized.

Presence of thallium in the environment: sources of contaminations, distribution and monitoring methods.

Thallium is released into the biosphere from both natural and anthropogenic sources. It is generally present in the environment at low levels; however, human activity has greatly increased its content. Atmospheric emission and deposition from industrial sources have resulted in increased concentrations of thallium in the vicinity of mineral smelters and coal-burning facilities. Increased levels of thallium are found in vegetables, fruit and farm animals. Thallium is toxic even at very low concentrations and tends to accumulate in the environment once it enters the food chain. Thallium and thallium-based compounds exhibit higher water solubility compared to other heavy metals. They are therefore also more mobile (e.g. in soil), generally more bioavailable and tend to bioaccumulate in living organisms. The main aim of this review was to summarize the recent data regarding the actual level of thallium content in environmental niches and to elucidate the most significant sources of thallium in the environment. The review also includes an overview of analytical methods, which are commonly applied for determination of thallium in fly ash originating from industrial combustion of coal, in surface and underground waters, in soils and sediments (including soil derived from different parent materials), in plant and animal tissues as well as in human organisms.

Stability of Tl(III) in the context of speciation analysis of thallium in plants.

The paper presents both "good" and "bad" results obtained during speciation analysis of thallium in plant tissues of a hyperaccumulator of this metal. The object was white mustard - Sinapis alba L. In this plant there were found traces of trivalent thallium. The crucial point of this study (especially in the case of so unstable thallium form as Tl(III)) was to prove that the presence of Tl(III) was not caused by the procedure of sample preparation itself, and that the whole analytical method provides reliable results. Choice of the method for conservation of the initial speciation, extraction with the highest efficiency and proving the correctness of the obtained data were the most difficult parts of the presented study. It was found that: both freezing and drying cause significant changes in the speciation of thallium; quantitative analysis could be performed only with fresh tissues of mustard plants; only short-term storage of an extract from fresh plant tissues is possible; the methodology is not the source of thallium (III); only the presence of DTPA can greatly limit the reduction of TI(III) to TI(I) (up to 1-3%); the UV irradiation results in disintegration of TI(III)DTPA in the presence of plant matrix (reduction up to 90%).

Отруєння талієм та його сполуками

Талій — хімічний елемент III групи періодичної системи, сріблясто-білий метал з сіруватим відтінком, без смаку й запаху. Талій використовується як інсектицид та зооцид, як каталізатор при проведенні феєрверків, у вигляді домішки для отримання сплавів у радіологічних дослідженнях, у виробництві оптичного скла, фотоелементів, як компонент легкоплавких і підшипникових сплавів. Талій за токсичністю належить до 1-го класу, гранично допустима концентрація в повітрі робочої зони становить 0,1 мг/м3. Гранично допустима концентрація у воді — 0,0001 мг/м3, в атмосферному повітрі — 0,004 мг/м3. Джерелами надходження талію в довкілля є підприємства, що спалюють у процесі виробництва органічні вуглецеві палива. При потраплянні в організм талій абсорбується через шкіру, інгаляційним шляхом і при пероральному прийомі. Загальнорезорбтивна дія талію проявляється депонуванням його в усіх паренхіматозних органах, легенях, м’язах і головному мозку. Талій є ферментною отрутою, зв’язується з сульфгідрильними групами ферментів на мембранах мітохондрій у внутрішньоклітинних ділянках. Механізм дії талію зводиться до втручання його в процес окисного фосфорилювання. У малих кількостях талій підвищує активність АТФази, у великих кількостях — пригнічує її активність. Порушуючи тканинне дихання, талій зумовлює дистрофічні зміни в мітохондріях, насамперед у нервових волокнах, руйнуючи аксони. Відразу після потрапляння талію в організм (протягом 3–4 год) розвиваються диспептичні явища: блювання й нудота, болі в животі, пронос і кров’янисті випорожнення, можуть бути запори. Згодом (протягом 1 тижня після проковтування) з’являються ознаки ураження центральної нервової системи у вигляді астеновегетативного синдрому, астеноневротичного, включаючи сплутаність і порушення свідомості, психоз, хореоатетоз, синдром органічного ураження головного мозку, галюцинаторний синдром, судоми та кому. До числа проявів ураження периферичної нервової системи належить синдром вегетосенсорної та вегетомоторної полінейропатії. До числа хронічних проявів отруєння належить дифузне випадання волосся, наявність астеновегетативного, астеноневротичного, діенцефального, психоорганічного та інших синдромів. Хронічні ураження сполуками талію паренхіматозних органів проявляються токсичним гепатитом, токсичною нефропатією, міокардіодистрофією. Часто спостерігаються ерозивні езофагогастроентероколіти із розвитком постгеморагічної анемії. Талій у сечі можна виявити лише за допомогою атомно-адсорбційної спектрофотометрії. Рівень 2 мкг/л у сечі вважають допустимим, а 20 мкг/л — таким, що викликає симптоми хронічного отруєння. Може бути підвищена амінолевулінова кислота в сечі. Терапевтичні заходи при потраплянні сполук талію до організму включають очищення шлунково-кишкового тракту за допомогою сорбентів, посилення ниркової екскреції сечогінними засобами, хлоридом калію. Застосовують гемодіаліз, гемосорбцію, ентеросорбцію. Прусський блакитний як антидот абсорбує талій в шлунково-кишковому тракті, обмінюючи калій на талій у його кристалічній решітці, тим самим запобігаючи всмоктування останнього в кров. Одноразова пероральна доза дорівнює 250 мг/кг.

Various Methods for Synthesis of Bulk and Nano Thallium(III) Oxide

Thallium(III) oxide, a degenerate n-type semiconductor, is a highly insoluble thermally stable thallium source suitable for glass, optic and ceramic applications. Although thallium oxide is an important metal oxide, its synthesis has only been sporadically studied. This review gives an overview of all reported synthetic routes for the preparation of both bulk and nanostructured thallium(III) oxide. These methods include electrochemical methods, thermal method, chemical vapor deposition (CVD), microwave irradiation, sol–gel method and one recently chemical route using potassium superoxide. In electrochemical methods, both bulk and nanostructures of thallium(III) oxide can be prepared and the amount of the deposited material, thickness of the layer or wires length depends on the deposition time matrix structure. Thermal methods are simple and effective techniques which include thermal decomposition and calcination of various precursors. By CVD and microwave irradiation we be able to synthesis bulk and nanostructures of thallium(III) oxide, respectively. A one-step, room temperature, solution synthesis of thallium(III) oxide nanoparticles with a size of about 10 nm is reported by using potassium superoxide.

Miocene colored waters: A new significant source of thallium in the environment

Thallium is a toxic non-essential element which is subject to some dispersion in the environment due to industrial activity and natural processes. There is a need for this dispersion to be monitored. Colored Miocene water seems to be a newly discovered significant source of such dispersion.The presence of colored water within the brown coal Miocene formation is related to the formation of organic sediments in that period which changed into layers of brown coal.The aim of this study was to investigate the concentration of Tl in colored waters, both in soluble form and entrapped in suspended solid matter (SS). Tl was determined by flow-injection differential-pulse anodic stripping voltammetry (FI-DP-ASV).It was found that Miocene colored waters from the Wielkopolska region contain very high Tl concentrations, and are thus a newly discovered significant source of Tl pollution in the environment. The concentrations are higher than the results for surface water by 2–3 orders of magnitude, and are a serious cause for concern. The majority of the total Tl in the colored waters is entrapped in suspended solids (more than 95% in the majority of samples). Even a low percentage of soluble Tl, however, creates a high concentration of the element in water (median 0.11μgL−1), which is approximately 10 times higher than in surface water from the River Warta. Tl concentration in SS is very high (median 15μgg−1) and exceeds by one order of magnitude the concentration of the element in crude Zn–Pb ores.

Distribution, enrichment and sources of thallium in the surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea

The concentrations of thallium (Tl) in the surface sediments of the southwestern coastal Laizhou Bay and the rivers it connects were determined. In riverine sediments, the Tl concentrations ranged from 0.34 to 0.76μgg−1 in summer; in autumn, the corresponding data were 0.35–1.08μgg−1. In marine sediments, the Tl concentrations ranged from 0.36 to 0.58μgg−1 in summer; and from 0.30 to 0.56μgg−1 in autumn. The grain size, Al and Fe oxides were major factors affecting Tl distribution. Tl in the surface sediments of the studied area was mainly from the natural input with the non-natural input as a subsidiary source. The low concentrations of Tl made it hard to cause potential negative environmental effects in this area.

Thallium toxicosis in a dog consequent to ingestion ofMycoplasmaagar plates

A 1-year-old dog ingested a mixture of blood agar and Mycoplasma agar plates. The Mycoplasma agar plates contained thallium acetate, which resulted in an estimated minimum dose of 5 mg thallium acetate/kg bodyweight. Clinical signs over the course of 2-3 weeks included vomiting, diarrhea, weight loss, alopecia, dysphonia, ataxia, paresthesia, intension tremors, megaesophagus with subsequent aspiration pneumonia, and several seizure episodes. The dog was treated with intravenous fluids and placement of a gastric feeding tube. Thallium concentrations in hair were 8.2 µg/g in samples taken on day 19, 16.4 µg/g in samples taken 3 months after exposure, 13.4 µg/g in samples taken 5 months after exposure, and nondetectable in samples taken 7 months after exposure. The blood thallium concentration was 190 µg/l on day 19 and nondetec table 3 months after exposure. Megaesophagus and dysphonia continued for 10 months after exposure. This case of thallium poisoning following ingestion of mycoplasma agar plates demonstrates that unusual sources of thallium still exist and suggests that thallium toxicosis should be included in the list of differential diagnoses in dogs presented with megaesophagus, especially if alopecia and other unexplained peripheral neuropathies are present. Hair and blood samples are useful specimens to reach an accurate diagnosis even if taken several weeks post exposure. The postexposure blood and hair thallium concentrations reported in this case are useful data for diagnosticians investigating dogs with potential thallium poisoning.

Superconducting Properties of Spray Deposited TBCCO Films

The present study shows general characteristic features of processes such as spray pyrolysis and heat-treatment, involved in the preparation of Tl-2223/CeO2/Al2O3 superconducting coatings by using aerosol pyrolysis method. The importance of the present study, however, lies in a new process to make a thick Tl-2223 superconducting layer by using spray pyrolysis. In the new method, a relatively thick BaCaCuO precursor film is firstly spray deposited on the buffered alumina substrate and then heat-treated in the presence of thallium source for phase transformation to superconducting phases to assign conductivity to the film. The thickness of the Tl-2223 layer was 2–3 μm. The crystal symmetry was found to be tetragonal with lattice parameters a=3.85, and c=35.7 A. The Tc was found to be 98 K for the samples heat treated at 870 °C for 60 min. Magnetic characterizations were conducted by using a DC-SQUID magnetometer. From the magnetization measurements, the intragrain critical-current density, Jc, was calculated to be 2×104 A/cm2 at 70 K.

Investigations on TlBa 2Ca 2Cu 3O x superconducting thin films formation on LaAlO 3 substrate

Investigations on pure superconducting phase TlBa 2Ca 2Cu 3O x (Tl-1223) thin films formation, of about 100–125 nm in thickness, on (001) LaAlO 3 single crystal substrate, were made using radio-frequency sputtering deposition of Ba 2Ca 2Cu 3O x precursor films and ex-situ thallination in sealed quartz tube. The precursor films were thallinated under different conditions of partial oxygen pressure, temperature, time and y thallium source content using unreacted pellets of composition Tl y Ba 2Ca 2Cu 3O x . In all cases, strongly c-oriented multiphase films were obtained. A correlation between the Tl-1223 phase purity and the precursor film conditions of thallination is established. Temperature and time of thallination as well as the thallium source content and the partial pressure of oxygen play a key role in the quality of the obtained film. The films' onset temperature of the superconducting transition ranges between 90 and 103 K. It is shown that the best samples can be obtained from a dense precursor film and relatively medium thallination time.

Thallium Based Superconducting Thin Films Synthesized by RF-Sputtering and <i>Ex Situ</i> Thallination

Thallium based superconducting thin films of TlBa2CaCu2O7 (Tl-1212), Tl2Ba2CaCu2O8 (Tl-2212) and Tl2Ba2Ca2Cu3O10 (Tl-2223) of about 100-125 nm in thickness have been prepared on (001) LaAlO3 single crystal substrate using rf-sputtering deposition of Ba2Ca2Cu3O7 precursor films and ex-situ thallination in sealed quartz tube under different atmospheres (oxygen, argon and nitrogen). We have studied phases formation as function of partial pressure of Tl2O which may be adjusted by varying thallium source content TlxBa2Ca2Cu3Oz (x = 1.5, 1.6, 1.7, 1.8, 1.9, 2.0) and atmosphere pressure at ambient temperature (300, 500 mbar). The influence of the temperature and time of thallination (60 min to 1400 min) is also presented. The synthesized films were characterised by optical microscopy, atomic force microscopy AFM, AC susceptibility and XRD measurements. The XRD measurement shows that the obtained films contain several superconducting phases and are strongly c-axis oriented. The properties of the resulting films are critically dependant on the microstructures developed during thallination process. Thallium source content as well as the time of thallination and partial atmosphere pressure at room temperature play an important role in the obtained film’s quality and phase’s purity.

Tl-based superconducting films by spray pyrolysis and MOCVD

Tl-1223 and Tl-2223 superconducting films have been prepared using spray pyrolysis and MOCVD for the deposition of the precursor layer and a solid source of thallium for the subsequent thallination step. For the former phase, critical temperatures and critical current densities up to 113 K and 2.5 MA/cm2 (77 K, 0 T) have been obtained after 3 to 6 hours at 860-870°C. Pure Tl-2223 films are by far more difficult to prepare. This can be achieved by operating at 890-900°C or with a fluorine containing source. The resulting films have then poor superconducting properties due to the presence of holes. Working at 875°C yields multiphase films (Tl-2223 + Tl-2212 or Tl-2223 + Tl-1223) with however better properties

Influence of different factors on the crystallization of Tl 2223/LAO superconducting films deposited by spray pyrolysis

The elaboration of Tl-2223 films by a two step process has been investigated. The films contain both Tl-2212 and Tl-2223 phases. We find that the kinetics for the Tl-2212 → Tl-2223 transformation is very slow due to the texture of the Tl-2212 phase. Critical current densities up to 1.3 MA/cm 2 (self-field, 77 K) are however measured. Pure Tl-2223 is obtained when the films are thallinated with a fluorinated source of thallium.

Highly toxic thallium in plants from the vicinity of Olkusz (Poland)

Thallium is a highly toxic metal that plays no role in the metabolism of plants or animals. Recent studies using small mammals and bird feathers as bioindicators demonstrated for the first time that animals from the vicinity of the Bolesław metal works near Olkusz (southern Poland) had large amounts of thallium in their tissues. Because of concern over these reports, four plant species ( Plantago lanceolata, Biscutella laevigata, Dianthus carthusianorum, Silene vulgaris) growing wildly in the same area on a 100-year-old calamine waste heap, as well as the waste heap soil, were examined. The average concentration of thallium in the waste heap soil was 43 mg Tl/kg dry wt, with the highest value 78 mg Tl/kg dry wt. P. lanceolata accumulated extremely large amounts of thallium (average, 65 mg Tl/kg dry wt; maximum 321 mg Tl/kg dry wt in roots). S. vulgaris and D. carthusianorum accumulated much less (averages, 10 and 6.5 mg Tl/kg dry wt, respectively). On the other hand, B. leavigata accumulated negligible amounts of thallium in its tissues. The concentration of thallium in plants (shoots, roots) from the calamine waste heap was 100–1000 times the level normally found in plants (0.05 mg Tl/kg dry wt). Possible sources of thallium are discussed and the urgent need for large-scale studies on thallium contamination of soils and vegetation in Poland, especially its southern regions, which are the most industrialized, is pointed out.

Thallium content in Zagreb air.

Thallium is present in raw materials and can significantly increase environmental exposure on local and regional level (IPCS, 1996). It is present in the air in relatively small amounts and in most countries it is not included in general monitoring practice. Thallium is mainly released in the air by mineral smelters, power-generating plants, and cement plants (ATSDR, 1992). Deterioration of building material could be considered as a significant source of thallium contamination in urban areas. The main source of thallium is the re-dispersion of dust from the contaminated soil as a disperse pollution source, covering an entire city. The only cement plant in Zagreb was the main source of thallium and was shut down approximately 15 years ago, so we can assume that no significant new deposition occurred during the last decade. The contribution of two large power plants with 200 meter smokestacks as point sources which disperse the pollution over vast areas may be considered negligible. Croatian legislation (Ordinance, 1996) prescribes only the limit value for a monthly amount of thallium in deposited matter (a large particle fraction) there are no limit values for thallium concentrations in the ambient air (suspended particulate matter). In order to get an insight into thallium levels in the Zagreb environment, thallium content in total suspended particulate matter, and its content in deposited matter was investigated for three consecutive years at two urban sites.