Evaluating levels and health risk of heavy metals in exposed workers from surgical instrument manufacturing industries of Sialkot,Pakistan

The study aimed to monitor heavy metal (chromium, Cr; cadmium, Cd; nickel, Ni; copper, Cu; lead, Pb; iron, Fe; manganese, Mn; and zinc, Zn) footprints in biological matrices (urine, whole blood, saliva, and hair), as well as in indoor industrial dust samples, and their toxic effects on oxidative stress and health risks in exposed workers. Overall, blood, urine, and saliva samples exhibited significantly higher concentrations of toxic metals in exposed workers (Cr; blood 16.30 μg/L, urine 58.15 μg/L, saliva 5.28 μg/L) than the control samples (Cr; blood 5.48 μg/L, urine 4.47 μg/L, saliva 2.46 μg/L). Indoor industrial dust samples also reported to have elevated heavy metal concentrations, as an example, Cr quantified with concentration of 299 mg/kg of dust, i.e., more than twice the level of Cr in household dust (136 mg/kg). Superoxide dismutase (SOD) level presented significant positive correlation (p?≤?0.01) with Cr, Zn, and Cd (Cr?>?Zn?>?Cd) which is an indication of heavy metal’s associated raised oxidative stress in exposed workers. Elevated average daily intake (ADI) of heavy metals resulted in cumulative hazard quotient (HQ) range of 2.97–18.88 in workers of different surgical units; this is an alarming situation of health risk implications. Principal component analysis-multiple linear regression (PCA-MLR)-based pie charts represent that polishing and cutting sections exhibited highest metal inputs to the biological and environmental matrices than other sources. Heavy metal concentrations in biological matrices and dust samples showed a significant positive correlation between Cr in dust, urine, and saliva samples. Current study will help to generate comprehensive base line data of heavy metal status in biomatrices and dust from scientifically ignored industrial sector. Our findings can play vital role for health departments and industrial environmental management system (EMS) authorities in policy making and implementation.     

Microcalorimetric studies of perchlorate on heat production by hepatocytes and mitochondria isolated from Carassius auratus

As a new threat to environment all through the world, perchlorate (ClO(4)(-)) was predominantly a thyrotoxin, and its toxic manifestations in non-thyroid were also documented. However, little is known about the effects of ClO(4)(-) on cell and organelle. Therefore, the present study was designed to investigate the effects of ClO(4)(-) on hepatocytes and mitochondria isolated from Carassius auratus from the direct viewpoint of energy by using the microcalorimetric method. The metabolic thermogenic curves of hepatocytes and mitochondria at 25°C were obtained. And the thermokinetic parameters, such as growth rate constant (k), inhibitory ratio (I), maximum thermal power (P(max)) and total thermal effect (Q(total)) have been calculated. The results indicated that the toxicity of ClO(4)(-) on hepatocytes was relevant to the concentration of ClO(4)(-). However, 10-100mgL(-1)ClO(4)(-) stimulated the metabolic activity of mitochondria and the toxicity of ClO(4)(-) on mitochondria only occurrenced when treated with higher concentration of ClO(4)(-). This study shown that mitochondria has a major impact on the metabolic thermogenic of hepatocytes, but not the only factor. Meanwhile, it demonstrated that microcalorimetry was a powerful tool for understanding biological processes and studying on the toxic action of environmental contaminants in cell or subcellular level.     

Persistent organic pollutants in 9/11 world trade center rescue workers: reduction following detoxification

Exposure to toxins following the September 11, 2001 attack on and collapse of the World Trade Center (WTC) is of particular concern given the ultra fine particulate dust cloud, high temperature combustion, and months-long fire. Firefighters, paramedics, police and sanitation crews are among the approximately 40000 personnel who labored for weeks and months on rescue and cleanup efforts. Many of the rescue workers have subsequently developed symptoms that remain unresolved with time. This study characterizes body burdens of polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dioxins (PCDDs) in rescue workers and citizens exposed following the WTC collapse. Our research includes a pilot evaluation of a detoxification method aimed at reducing toxic burden. Many congeners were found at elevated levels, in ranges associated with occupational exposures. Post-detoxification testing revealed reductions in these congeners and despite the small study size, some reductions were statistically significant. Health symptoms completely resolved or were satisfactorily improved on completion of treatment. These results argue for a larger treatment study of this method and an overall treatment approach to address toxic burden.     

Monitoring and identification of airborne asbestos in unorganized sectors, India

Rajasthan state in India is credited to cater more than 90% of total production of asbestos in this country, of which around 60% is processed there in unorganized sectors including milling and manufacturing of asbestos-based products. Unorganized asbestos units particularly mills showed unhealthy occupational conditions, therefore industrial hygiene study was carried out focusing on the prevalence of asbestos fibres in air at work zone area of asbestos milling units. Fibre levels were in the range of 2.00-5.09f/cm(3) and 4.07-15.60f/cm(3) in unorganized asbestos mills of Rajasthan located at Beawer and Deogarh districts, respectively. Like asbestos concentration, fibre type and length are also vital factors in the health risk assessment of industrial workers. Phase contrast and polarized light microscopic study of asbestos fibres showed their amphibole nature registering about 90% as tremolite and rest as anthophyllite. Fibre length measured micrometrically were sub-grouped in <10microm, 11-20microm, 21-30microm and >30microm. About 30-40% fibres belonged to sub-group <10microm. It is concluded that unorganized asbestos mills bear poor industrial unhygienic conditions reflected specifically from their manyfold higher fibre concentrations than the Indian and International standards. Poor industrial unhygienic conditions are attributable to obsolete milling technology, lack of pollution control devices and escape from regulatory control.     

PCB contaminated dust on indoor surfaces--health risks and acceptable surface concentrations in residential and occupational settings

Polychlorinated biphenyls (PCBs) have been used in diverse purposes such as indoor paints. Removal of these paints with dust creating techniques, like sandblasting, will result in contamination of building surfaces with PCB-containing dust. Objectives of this study was to analyze the PCB concentrations on surfaces after sandblasting with silica using wipe samples and estimate the resulting health risks and further calculate the risk based acceptable PCB surface concentrations that do not cause incremental lifetime cancer risk higher that 10(-5) or does not cause immunosupression effects in residential use or in occupational settings. Both deterministic and probabilistic approaches were used. The total PCB concentrations on surfaces ranged from 10 to 1100 microg/m(2). Estimated cancer risk was 1.2 x 10(-4) for childhood exposure, 1.3 x 10(-5) for adult residents and 1.5 x 10(-5) for occupational exposure. Probabilistic risk assessment revealed that point estimates were quite reasonable and located between 45th and 79th percentiles on probabilistic distribution of risk. The noncancer risks were calculated as hazard quotients (HQ) which ranged from 3.3 to 35 depending on the exposure scenario. Acceptable surface concentrations based on noncancer effects that are protective for 95% of exposed population were 7 microg/m(2) for residential use, 65 microg/m(2) for residential use if only adults will be exposed and 140 microg/m(2) for occupational use. Preliminary cleanup experiment revealed that when contaminated dust was carefully removed with industrial vacuum cleaner and further washed with terpene containing liquid the surface concentration dropped below the acceptable levels calculated in this study.     

Toxicity and oxidative stress induced by chromium in workers exposed from different occupational settings around the globe: A review

The present review focused on the levels and toxicological status of heavy metals especially chromium (Cr) in the exposed workers from different occupational settings around the globe and in Pakistan. It was found that exposed workers from leather tanning and metal plating units showed elevated levels of Cr than the workers from other occupational settings. Cr and other heavy metals level in biological matrices of the exposed workers in different occupational settings revealed that developing countries are severely contaminated. Occupational settings from the Sialkot district, Pakistan exhibited elevated level of Cr in biological entities of the exposed workers. Review suggested that higher level of Cr exposure to the workers enhance the oxidative stress (reactive oxygen species (ROS) and hydroxyl (OH) radical generation) which may cause; cellular and molecular damage such as genotoxicity and chromosomal aberration formations, and carcinogenic effects. This review will help to understand the Cr contamination mechanisms and associated health implications in different occupational settings around the globe in general and particularly to Pakistan. This study will also assist occupational health and safety management authorities to devise or change the Cr recommended exposure limits (REL) for different occupational settings.     

Biological and chemical tools in the toxicological risk assessment of Jarama River, Madrid, Spain

Four river water samples (R) and three sewage samples (S) were collected at different points in the Jarama River, Spain. Organic concentrates were tested on the RTG-2 in vitro cytotoxicity test and analyzed by HPLC and GC/MS. The cytotoxicity assessment demonstrated a progressive increase in the toxicity of the river water when moving downstream. A wide range, from slightly harmful to highly toxic, was observed for sewage samples. The most toxic samples produced decreases of 95% to 100% in the ATP content, cell viability and cell detachment (a parameter to estimate mortality). The most toxic organic concentrates (the sewage from an urban + industrial effluent collected in Paracuellos, Madrid, Spain, and the river 100 m downstream from the discharge of this effluent) were fractioned by an HPLC system. Each chromatographic peak was collected as a fraction of the whole concentrate. The cytotoxicity of each fraction was also assessed on RTG-2 cells. A toxic peak with a retention time of 38.3 min was detected in both samples; this time belongs to the PAHs retention time interval under our chromatographic conditions. Analytical procedures identified fluorene (0.62 microg/l) and benz(a)anthracene (0.44 microg/l) in the sewage and anthracene (0.40 microg/l) and benz(a)anthracene (0.14 microg/l) in the river water. However, the observed cytotoxicity could not be explained by the PAH concentrations. Five additional toxic peaks were observed in each sample. Results suggest that the combination of HPLC with cost-effective toxicity tests produces a useful tool to define environmental management decisions when the chemical analysis cannot identify the substances responsible for the environmental risk.     

PCDD and PCDF exposures in workers and controls living near an industrial waste incinerator

This study measured the levels of 17 congeners of PCDDs/PCDFs in serum to compare the levels between potentially exposed workers at an industrial waste incinerator and any residents with no known exposures. The 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD were detected in serum of workers but in controls. Likewise, 1,2,3,7,8-PeCDF, 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDF were detected only in serum of workers. The international toxic equivalent (TEQ) levels of PCDDs/PCDFs in sera of workers are much higher than in controls. Among PCDDs, the proportion of total concentration and TEQ level is dominated predominantly by 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD. We need extensive studies to estimate human exposure and are continuing this investigation.     

Polybrominated diphenyl ether exposure to electronics recycling workers--a follow up study

Workers at an electronics recycling plant have previously been shown to have elevated serum levels of polybrominated diphenyl ethers (PBDEs) compared to referents without occupational PBDE exposure. Subsequent structural changes and industrial hygiene measures at the plant were applied to improve the work environment. The present study aims to assess the impact of these work environment changes on the occupational exposure to PBDEs.

Blood were drawn from the workers and analyzed at two different laboratories, and serum concentrations of several PBDE congeners were determined by GC/MS or GC/HRMS. Cross-sectional studies were performed prior to (in 1997; N = 19) and after (in 2000; N = 27) workplace improvements. Longitudinal studies were performed on twelve of the workers that were sampled at both occasions.

Even though the amount of processed goods had doubled in 2000 as compared to 1997, there was a significant decrease in the serum levels of BDE-183 and BDE-209. For BDE-209 the levels observed in year 2000 were even lower than in referents with no occupational exposure. In contrast to the decrease of higher brominated diphenyl ethers, the concentrations of BDE-47 did not significantly change. For BDE-153, the cross-sectional study indicated no change, whereas the longitudinal follow up indicated a significant increase.

This study shows that the industrial hygiene improvements clearly reduced the occupational exposure to BDE-183 and BDE-209 at the plant. Still, the levels of hexa- to nonaBDEs but not BDE-209 were elevated, compared to referents with no occupational exposure.     

Spore release by the green alga Ulva: a quantitative assay to evaluate aquatic toxicants

A toxicity test using spore release of the aquatic green alga, Ulva, was developed and evaluated by assessing the toxicity of different organic and inorganic chemicals and elutriates of sewage or waste sludge. The toxic ranking of four metals was: Cu (EC50 of 0.040mgL(-1))>Cd (0.095mgL(-1))>Pb (0.489mgL(-1))>Zn (0.572mgL(-1)). The EC50 for TBTO ranged from 24 to 63microgL(-1). The most toxic VOC was formalin (EC50 of 0.788microlL(-1)) and the least toxic was acetone. Spore release was significantly inhibited in all elutriates; the greatest and least toxic effects were for industrial sewage (3.29%) and filtration bed (10.08%), respectively. The bioassay is simple, inexpensive and sensitive. The cosmopolitan distribution of Ulva means that the test would have a potential application worldwide.     

Status of industrial fluoride pollution and its diverse adverse health effects in man and domestic animals in India

Hydrofluorosis in humans and domestic animals is a worldwide health problem and caused by a prolonged period of fluoride exposure through drinking of fluoride contaminated water. But in recent years, due to rapid industrialization in India, diverse serious health problems among industrial workers and residents and domestic animals living in the industrial areas due to fluoride pollution are on the rise. A number of coal-burning and industrial activities such as power-generating stations, welding operations and the manufacturing or production of steel, iron, aluminum, zinc, phosphorus, chemical fertilizers, bricks, glass, plastic, cement, and hydrofluoric acid are generally discharging fluoride in both gaseous and particulate/dust forms into surrounding environments which create a industrial fluoride pollution and are an important cause of occupational exposure to fluoride in several countries including India. An industrial emitted fluoride contaminates not only surrounding soil, air, and water but also vegetation, crops and many other biotic communities on which man and animals are generally dependants for food. Long- time of inhalation or ingestion of industrial fluoride also causes serious health problems in the forms of industrial and neighborhood fluorosis. In India, whatever research works conducted so far on the chronic industrial fluoride intoxication or poisoning (industrial and neighborhood fluorosis) in man and various species of domestic animals due to a prolonged period of industrial fluoride exposure or pollution (contamination) are critically reviewed in the present communication. Simultaneously, we are also focused the various bio-indicators and bio-markers for chronic industrial fluoride intoxication or pollution.     

Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO

This work reports a preliminary study of semiconductor-assisted photochemical degradation of lignin, Remazol Brilliant Blue R and Kraft E1 paper effluent by using ZnO and Ag-doped ZnO photocatalysts. The doped semiconductor was prepared in the reaction media by photoreduction of silver nitrate. With the use of 100 mg of ZnO and 15 mg of Ag-ZnO, almost total decolorization of the dye and lignin samples in reaction times lower than 60 min were observed. Extending the photochemical reaction up to 120 min, the total organic carbon content (TOC) was reduced in 90%. For the paper effluent, a fast decolorization was obtained for relatively short reaction times. However, de TOC reduction was negligible (near of 10%) up to high reaction times (300 min). By using the Ag-ZnO photocatalyst, the toxicity of lignin and Kraft E1 effluent toward E. Coli was completely removed. For the dye, the formation of transient toxic species was observed.     

Toxic effects of anthraquinone and phenanthrenequinone upon Scenedesmus strains (green algae) at low and elevated concentration of CO2

Short-term (24h) experiments were performed to examine the effect of anthraquinone (ANTQ) and phenanthrenequinone (PHEQ) on two Scenedesmus armatus strains (B1-76 and 276-4d) grown in a batch culture system aerated with CO2 at a low (0.1%) or elevated (2%) concentration. ANTQ at concentrations within the range of 0.156-1.250 mg dm-3 inhibited the growth of B1-76 population in a concentration-dependent manner, and calculated EC50 for low-CO2 cells was 0.56 mg dm-3. The toxic effect of ANTQ on this strain was more pronounced in high-CO2 cells, where not only growth but also photosynthesis, respiration and SOD activity were significantly inhibited. In contrast, except for SOD activity, no ANTQ effects on strain 276-4d were found. PHEQ at concentrations within the range of 0.063-0.125 mg dm-3 inhibited the growth of B1-76 population in a concentration-dependent manner. The value of EC50 for low-CO2 B1-76 cells was 0.10 mg dm-3. PHEQ inhibited the growth of both strains regardless of CO2 concentration. In B1-76 cells affected by PHEQ, inhibition of photosynthesis was independent of the CO2 level, whereas the SOD activity was much higher in cultures aerated with 2% than with 0.1% CO2. Higher toxicity of PHEQ to strain 276-4d grown at 2% CO2 was accompanied by strong inhibition of photosynthesis, while in low-CO2 cells this process was slightly stimulated. The SOD activity in both low- and high-CO2 cells of strain 276-4d treated with PHEQ was 2-3 times higher compared with the controls. The pattern of SOD isoforms (PAGE analysis) obtained from cells exposed to ANTQ or PHEQ did not change compared with the controls, but the location of the SOD isoforms bands on gel was affected by the concentration of CO2. The results suggest that the strain-specific toxicity of ANTQ and PHEQ may result from oxidative stress. In addition, carbon dioxide appears to play an important role in the toxicity of quinones to algae.     

PCDD/F and metal concentrations in soil and herbage samples collected in the vicinity of a cement plant

Juvenoids are biologically active compounds, of relatively low toxicity to humans, that efficiently inhibit the fertility of insects. However, little attention has been paid to the stability and toxicity of products that may be generated by their biodegradation in the ecosystem. This study describes a simple comparison of the toxicity of the active compound and its degradation products generated by aerobic soil microbial isolates. Surprisingly we have found that toxicity of a biologically active carbamate juvenoid N-[2-[4-(2,2-ethylenedioxy-1-cyclohexylmethyl)-phenoxylethyl]carbamate (W328) was comparable with that of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT). The toxic effect was evaluated using the determination of the ATP/ADP content and viability of HeLa S3 cells exposed to various concentrations of the chemicals tested for various durations. DDT was used as a reference compound. Its toxicity was compared with two juvenile hormone analogs. The original compound, W328, was found to be the most toxic. The major product (W329) generated both by yeast isolates and the mixture of moulds lost its activity on reproduction of the tested insect. Its toxicity towards human cells was also decreased. Another two W328 degradation HPLC fractions exhibited significantly reduced toxicity compared to W328.     

Fate of ah receptor agonists during biological treatment of an industrial sludge containing explosives and pharmaceutical residues

GOAL, SCOPE AND BACKGROUND: Sweden is meeting prohibition for deposition of organic waste from 2005. Since 1 million tons of sludge is produced every year in Sweden and the capacity for incineration does not fill the demands, other methods of sludge management have to be introduced to a higher degree. Two biological treatment alternatives are anaerobic digestion and composting. Different oxygen concentrations result in different microbial degradation pathways and, consequently, in a different quality of the digestion or composting residue, It is therefore necessary to study sludge treatment during different oxygen regimes in order to follow both degradation of compounds and change in toxicity. In this study, an industrial sludge containing explosives and pharmaceutical residues was treated with anaerobic digestion or composting, and the change in toxicity was studied. Nitroaromatic compounds, which are the main ingredients of both pharmaceutical and explosives, are well known to cause cytotoxicity and genotoxicity. However, little data are available concerning sludge with nitroaromatics and any associated dioxin-like activity. Therefore, we studied the sludge before and after the treatments in order to detect any changes in levels of Ah receptor (AhR) agonists using two bioassays for dioxin-like compounds. METHODS: An industrial sludge was treated with anaerobic digestion or composting in small reactors in a semi-continuous manner. The same volume as the feeding volume was taken out daily and stored at -20 degrees C. Sample preparation for the bioassays was done by extraction using organic solvents, followed by clean up with silica gel or sulphuric acid, yielding two fractions. The fractions were dissolved in DMSO and tested in the bioassays. The dioxin-like activity was measured using the DR-CALUX assay with transfected H4IIE rat hepatoma pGudluc cells and an EROD induction assay with RTL-W1 rainbow trout liver cells. RESULTS AND DISCUSSION: The bioassays showed that the sludge contained AhR agonists at levels of TCDD equivalents (TEQs) higher than other sludge types in Sweden. In addition, the TEQ values for the acid resistant fractions increased considerably after anaerobic digestion, resulting in an apparent formation of acid resistant TEQs in the anaerobic reactors. Similar results have been reported from studies of fermented household waste. There was a large difference in effects between the two bioassays, with higher TEQ levels in the RTL-W1 EROD assay than in the DR-CALUX assay. This is possibly due to a more rapid metabolism in rat hepatocytes than in trout hepatocytes or to differences in sensitivities for the AhR agonists in the sludge. It was also demonstrated by GC/FID analysis that the sludge contained high concentrations of nitroaromatics. It is suggested that nitroaromatic metabolites, such as aromatic amines and nitroanilines, are possible candidates for the observed bioassay effects. It was also found that the AhR agonists in the sludge samples were volatile. CONCLUSIONS: The sludge contained fairly high concentrations of volatile AhR agonists. The increase of acid resistant AhR agonist after anaerobic digestion warrants further investigations of the chemical and toxic properties of these compounds and of the mechanisms behind this observation. RECOMMENDATION AND OUTLOOK: This study has pointed out the benefits of using different types of mechanism-specific bioassays when evaluating the change in toxicity by sludge treatment, in which measurement of dioxin-like activity can be a valuable tool. In order to study the recalcitrant properties of the compounds in the sludge using the DR-CALUX assay, the exposure time can be varied between 6 and 24 hours. The properties of the acid-resistant AhR agonists formed in the anaerobic treatment have to be investigated in order to choose the most appropriate method for sludge management.     

Levels and sources of brominated flame retardants in human hair from urban, e-waste, and rural areas in South China

Human hair and indoor dust from urban, e-waste, and rural areas in south China were collected and analyzed for brominated flame retardants (BFRs). BFRs concentrations in hair from occupational e-waste recycling workers were higher than those from non-occupational exposed residents in other sampling areas. Polybrominated diphenyl ethers (PBDEs) and decabromodiphenyl ethane (DBDPE) are two major BFRs in hair samples. The PBDE congener profiles in hair from the e-waste area are different from those from urban and rural areas with relatively higher contribution of lower brominated congeners. DBDPE, instead of BDE209, has become the major BFR in non-e-waste recycling areas. Significant correlations were found between hair level and dust level for DBDPE and BTBPE but not for PBDEs. The different PBDE congener profiles between dust and hair may suggest that exogenous exposure to the PBDE adsorbed on dust is not a major source of hair PBDEs.     

Genotoxic assessment on river water using different biological systems

This paper reports genotoxicity and toxicity data in water samples collected in Sinos River, an important water course in the hydrographic region of Guaíba Lake, Rio Grande do Sul State, south of Brazil. This river is exposed to intense anthropic influence by numerous shoes, leather, petrochemical, and metallurgy industries. Water samples were collected at two moments (winter 2006 and spring 2006) at five sites of Sinos River and evaluated using in vitro V79 Chinese hamster lung fibroblasts (cytotoxicity, comet assay and micronucleus test) and Allium cepa test (toxicity and micronucleus test). Comet and micronucleus tests revealed that water samples collected exerted cytotoxic, toxic, genotoxic and mutagenic effects. The results showed the toxic action of organic and inorganic agents found in the water samples in all sites of Sinos River, for both data collections. The main causes behind pollution were the domestic and industrial toxic discharges. The V79 and A. cepa tests were proved efficient to detect toxicity and genotoxicity caused by complex mixtures. This study also showed the need for constant monitoring in sites with strong environmental degradation caused by industrial discharges and urban sewages.     

Cytotoxicity to alveolar macrophages of airborne particles and waste incinerator fly-ash fractions

A waste incinerator fly ash was separated into different grain-size fractions by sieving and sedimentation in butanol. The element content of each fraction was determined by atomic absorption and emission spectrometry. The fly-ash fractions, an eluted fine fly-ash fraction and an eluted airborne dust were analysed microscopically for particle size and numbers, together with standard quartz DQ 12 and three element-analysed airborne dusts. Rabbit alveolar macrophages, isolated by lung lavage, were incubated for 24 h with the particulates, the two eluates and a mixed element compound solution corresponding to the element concentrations of one airborne dust. At the end of incubation, the activities of lactate dehydrogenase, N-acetyl-beta-glucosaminidase, beta-galactosidase and acid phosphatase were determined in medium and cell lysates. Cytotoxicity was expressed as ratio of extracellular to total LDH (lactate dehydrogenase) activity. Release of N-acetyl-beta-glucosaminidase and beta-galactosidase was correlated positively with LDH release, whereas the total activity of acid phosphatase decreased with increasing LDH release. Cytotoxicity of the dusts was correlated with particle numbers, and As, Sb and Pb contents. The contribution of As to particle toxicity is discussed. Eluates of dusts did not affect rabbit alveolar macrophage viability.     

Heavy metal contamination from mining sites in South Morocco: 1. Use of a biotest to assess metal toxicity of tailings and soils

Our work was conducted to investigate the heavy metal toxicity of tailings and soils collected from five metal mines located in the south of Morocco. We used the MetPAD biotest Kit which detects the toxicity specifically due to the heavy metals in environmental samples. This biotest initially developed to assess the toxicity of aquatic samples was adapted to the heterogeneous physico-chemical conditions of anthropogenic soils. Contrasted industrial soils were collected from four abandoned mines (A, B, C and E) and one mine (D) still active. The toxicity test was run concurrently with chemical analyses on the aqueous extracts of tailings materials and soils in order to assess the potential availability of heavy metals. Soil pH was variable, ranging from very acidic (pH 2.6) to alkaline values (pH 8.0-8.8). The tailings from polymetallic mines (B and D) contained very high concentrations of Zn (38,000-108,000 mg kg(-1)), Pb (20,412-30,100 mg kg(-1)), Cu (2,019-8,635 mg kg(-1)) and Cd (148-228 mg kg(-1)). Water-extractable metal concentrations (i.e., soil extracts) were much lower but were highly toxic as shown by the MetPAD test, except for soils from mines A, E and site C3 from mine C. The soil extracts from mine D were the most toxic amongst all the soils tested. On this site, the toxicity of soil water extracts was mainly due to high concentrations of Zn (785-1,753 mg l(-1)), Cu (1.8-82 mg l(-1)) and Cd (2.0-2.7 mg l(-1)). The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in tailings materials and soils. Therefore, the MetPAD test can be used as a rapid and sensitive predictive tool to assess the heavy metal availability in soils highly contaminated by mining activities.     

Formation of PCDD/Fs in the sintering process: role of the grid-Cr2O3 catalyst in the de novo synthesis

The sintering process is among the major sources of the very toxic polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in the environment. At the industrial scale, it has been shown that dust collected on the grid, which supports the feed, contains PCDD/Fs amounts between the values found in the bottom of the cake and the values found on dust collected during gas sampling in the wind boxes. This fact suggests that the grid, containing 25wt.% of chromium, could have a catalytic activity in PCDD/Fs formation during the sintering process. This research tries to study this potential role. The de novo synthesis of PCDD/Fs is simulated at laboratory scale by thermal treatments of samples mixed with grid filings or Cr2O3. The thermal experiments performed with E.S.P. dust (dust collected in the electrostatic precipitator of a sintering plant) or graphite mixed with grid filings do not allow to confirm a role of the grid in PCDD/Fs formation during the industrial process. On the other hand, it has been shown that Cr2O3 can be considered as a catalyst in the de novo synthesis of PCDD/Fs. This compound takes place in the two steps of the de novo synthesis: the degradation of the carbon matrix as well as the chlorination reactions.