Cancer risk assessment of human exposure to polycyclic aromatic hydrocarbons (PAHs) via indoor and outdoor dust based on probit model.

In the present study, the polycyclic aromatic hydrocarbons (PAHs) in indoor dust and outdoor dust including road and window dust around the traffic road in Hunan Province, China, were sampled and detected. The ∑PAHs in indoor dust ranged from 5007-24,236 ng g(-1), with a median of 14,049 ng g(-1). The ∑PAHs in road dust ranged from 3644-12,875 ng g(-1), with a median of 10,559 ng g(-1). The ∑PAHs in window dust ranged from 803-12,590 ng g(-1), with a median of 5459 ng g(-1). Similar pattern of PAHs was observed in road and window dust except in H3W and H4W samples, which was dominated by naphthalene (Nap), benzo(b+k)fluoranthene (B(b+k)F), phenanthrene (Phe), and fluorine (Fle). Indoor dust showed slightly different PAHs profiles, which was dominated by Nap, fluoranthene (Fla) and Phe. Risk assessment indicated that dermal contact and dust ingestion exposure pathways were more important than the inhalation pathway. Cancer risk of PAHs via dust varied from 2.73 × 10(-8)-8.04 × 10(-6), with a median of 2.06 × 10(-6) for children, and from 2 × 10(-8)-5.89 × 10(-6), with a median of 1.52 × 10(-6) for adult. Probit model showed that 76 and 71 % of samples in the sampling area would result in the risk of children and adult exposure to PAHs via dust higher than the acceptable level (1 × 10(-6)), respectively.

Concentrations, sources, and risk assessment of polychlorinated biphenyls in vegetables near a waste-incinerator site, South China.

Numerous studies have reported polychlorinated biphenyl (PCB) concentrations in soil, root, and aerial parts of vegetables. However, few studies have measured the contribution of PCBs bound to particles in air in relation to uptake by vegetables. In the present study, PCB concentrations were measured in five types of vegetables, soil, and settled air particle samples from two sites (at a domestic waste incinerator and at 20 km away from the incinerator) in Guangzhou, South China. ∑PCB concentrations in rhizosphere soil samples from the two sites ranged from 17.2-77.7 to 5.48-25.57 ng/g, respectively. ∑PCB concentrations in aerial parts of vegetables were greater than those in rhizosphere soils and roots with median values of 108 and 47.08 ng/g, respectively. Among the five types of vegetables studied, the highest concentration of PCBs was found in bitter lettuce. No significant correlation between PCBs in soil and roots or aerial parts of vegetables was observed. However, principal component analysis indicated that settled air particles were the dominant source of PCBs in the aerial parts of vegetables. In addition, similar PCB congener profiles were found in the aerial parts of vegetables and settled air particles. This suggests that foliar uptake of PCBs is an important pathway. Risk assessment indicated that human exposure to PCBs by way of dietary intake of vegetables from incinerator sites would result in high risk.

Risk assessment of arsenic and other metals via atmospheric particles, and effects of atmospheric exposure and other demographic factors on their accumulations in human scalp hair in urban area of Guangzhou, China.

Eighty-eight scalp hair samples were collected from Guangzhou (GZ) urban population (15-65 years) to investigate the accumulation of As and other metals (Cr, Mn, Ni, Cu, Zn, Cd, Sn, Sb, Hg and Pb). Demographic information, including body weight, height, age, gender, habits of smoking and drinking, types of drinking water, duration of stay in GZ, days of stay in GZ per year (days/year), and hours spent in indoor environment per day (h/day), were also recorded during hair sampling to refine the uncertainty of risk assessment derived from exposures to elements via dust and airborne particles. No significant non-carcinogenic risk was found. However, the cancer risks of Cr and As for both ingestion and inhalation exceeded the most tolerable regulated level (1.0×10(-6)). The environmental exposures to urban dust and airborne particles were observed significantly correlated to accumulations of Cd (R=0.306, p=0.005) and Ni (R=0.333, p=0.002) in scalp hair. Furthermore, the hair burden of elements was also significantly (p<0.05) dependent on gender (Mn, Ni, Zn, As, Sn and Hg), age (Cr, As, Cd and Hg), duration of stay in GZ (Hg) as well as nutritional and physical status, reflected by BMI and BSA (Cr, Ni, Cd, Sb and Hg). Nutritional and physical status was observed as the exclusive important factor influencing As speciation in human scalp hair. However, habits of smoking and alcohol drinking as well as types of drinking water were not identified as the significant influencing factors on any element (p>0.05).

Hair mercury levels and food consumption in residents from the Pearl River Delta: South China.

The Pearl River Delta (PRD) is located in the Southern part of China and is the main region for fish culture in Guangdong Province. In order to assess the potential health risks associated with dietary consumption of mercury, hair samples from 91 urban, town and fishing village residents, 37 species of fish, cereal, vegetables, and meat samples were collected. The average total mercury (THg) and methylmercury (MeHg) concentrations in hair were 1.08 ± 0.94 and 0.58 ± 0.59 µg/g, respectively. Daily Hg intake via fish consumption is significantly correlated with THg and MeHg accumulated in human hair (r=0.48, p<0.01; r=0.43, p<0.01). The estimated daily intake of Hg via different food types showed that both fish and cereal consumption were the two main routes of Hg exposure for residents in the sampling areas. Besides food intake, smoking was also an important source for daily THg intake in the smoke group, contributing 11-18% to EDI of THg.

Effects of sulfate reducing bacteria and sulfate concentrations on mercury methylation in freshwater sediments.

Methylmercury (MeHg) is the most poisonous form of mercury (Hg) and it enters the human body primarily through consumption of Hg contaminated fish. Sulfate reducing bacteria (SRB) are major producers of MeHg in anoxic sediments. The dsrAB gene was isolated from freshwater fish pond sediments. Sequence analyses showed that the SRB in sediments was mainly composed of Desulfobulbus propionicus and Desulfovibrio vulgaris. The two species of SRB were cultured from freshwater sediments. The addition of inorganic Hg to these freshwater sediments caused an increase in MeHg concentrations at 30 days incubation. MeHg levels were sensitive to sulfate concentrations; a medium sulfate level (0.11 mg/g) produced higher levels than treatments lacking sulfate addition or when amended with 0.55 mg/g. Assessment of bacterial levels by PCR measurements of microbial DNA indicated that the MeHg levels were correlated with cell growth.

Mercury biomagnification in the aquaculture pond ecosystem in the Pearl River Delta.

This is the first study to investigate the rate of mercury (Hg) biomagnification in the aquaculture pond ecosystem of the Pearl River Delta (PRD), China, by analyzing total mercury (THg) and methyl mercury (MeHg) concentrations in various species of fish at different trophic levels (TLs). Species representing a gradient of trophic positions in the aquaculture pond food chains were chosen for analyzing THg and MeHg concentrations. In this study, there were two kinds of the aquaculture pond food chains: (1) omnivorous (fish feeds, zooplankton, grass carp [Ctenopharyngodon idellus], and bighead carp [Aristichthys nobilis]) and (2) predatory (zooplankton, mud carp [Cirrhina molitorella], and mandarin fish [Siniperca kneri]). Bighead carp and mandarin fish had the highest MeHg and THg concentrations, i.e., an order of magnitude higher than other species, in their respective food chains. More than 90% of the THg concentrations detected in bighead carp, mandarin fish, and mud carp were in the methylated form. In this study, %MeHg increased with TLs and MeHg concentrations, reflecting that MeHg is the dominant chemical species of Hg accumulated in higher concentrations in biota, especially biota associated with higher TLs in the food chains. The trophic magnification factors were 2.32 and 2.60 for MeHg and 1.94 and 2.03 for THg in omnivorous and predatory food chains, respectively, in PRD. Hg concentrations in fish tissue correlated to Hg levels in the ambient environment, and sediment seemed to be the major source for Hg accumulated in fish. In addition, feeding habit also affected Hg accumulation in different fish species. Four significant linear relationships were obtained between log-THg and δ(15)N and between log-MeHg and δ(15)N. The slope of the regression equations, as biomagnification power, was smaller in magnitude compared with those reported for temperate and arctic marine and freshwater ecosystems, indicating that THg and MeHg biomagnifications were lower in this PRD subtropical aquaculture pond ecosystem. This was probably due to low Hg bioavailability at lower TLs as well as individual feeding behavior of fish.

Mercury species of sediment and fish in freshwater fish ponds around the Pearl River Delta, PR China: human health risk assessment.

This study investigated total mercury (THg) and methylmercury (MeHg) concentrations in five species of freshwater fish and their associated fish pond sediments collected from 18 freshwater fish ponds around the Pearl River Delta (PRD). The concentrations of THg and MeHg in fish pond surface sediments were 33.1-386 ng g(-1) dry wt and 0.18-1.25 ng g(-1) dry wt, respectively. The age of ponds affected the surface sediment MeHg concentration. The vertical distribution of MeHg in sediment cores showed that MeHg concentrations decreased with increasing depth in the top 10 cm. In addition, a significant correlation was observed between %MeHg and DNA from Desulfovibrionacaea or Desulfobulbus (p<0.05) in sediment cores. Concentrations of THg and MeHg in fish muscles ranged from 7.43-76.7 to 5.93-76.1 ng g(-1) wet wt, respectively, with significant linear relationships (r=0.97, p<0.01, n=122) observed between THg and MeHg levels in fish. A significant correlation between THg concentrations in fish (herbivorous: r=0.71, p<0.05, n=7; carnivorous: r=0.77, p<0.05, n=11) and corresponding sediments was also obtained. Risk assessment indicated that the consumption of largemouth bass and mandarin fish would result in higher estimated daily intakes (EDIs) of MeHg than reference dose (RfD) for both adults and children.

Levels, seasonal patterns, and potential sources of organochlorine pesticides in the urban atmosphere of Beijing, China.

Air samples collected monthly on the roof of a building in Beijing were analyzed for the levels, seasonal patterns, and potential sources of organochlorine pesticides (OCPs). A high-volume air sampler with polyurethane foam and quartz fiber filters was used to collect monthly samples from November 2005 to April 2009. Hexachlorobenzene (HCB) and DDT isomers were the most abundant organochlorinated pesticides in the Beijing atmosphere. Higher OCP concentrations were generally found in summer, except for HCB. Coal combustion, waste incineration, and fuel combustion were assumed to be the potential HCB emission sources. Significant input of either of these OCPs during our study period was considered very unlikely.

The influence of mariculture on mercury distribution in sediments and fish around Hong Kong and adjacent mainland China waters.

To study the influence of mariculture on mercury (Hg) speciation and distribution in sediments and cultured fish around Hong Kong and adjacent mainland China waters, sediment samples were collected from six mariculture sites and the corresponding reference sites, 200-300 m away from the mariculture sites. Mariculture activities increased total mercury, organic matter, carbon, nitrogen and sulfur concentrations in the surface sediments underneath mariculture sites, possibly due to the accumulation of unconsumed fish feed and fish excretion. However, methylmercury (MeHg) concentrations and the ratio of MeHg to THg (% MeHg) in sediments underneath mariculture sites were lower than the corresponding reference sites. The % MeHg in sediments was negatively correlated (r = -0.579, p < 0.05) with organic matter (OM) content among all sites, indicating that OM may have inhibited Hg methylation in surface sediments. Three mariculture fish species were collected from each mariculture site, including red snapper (Lutjanus campechanus), orange-spotted grouper (Epinephelus coioides) and snubnose pompano (Trachinotus blochii). The average MeHg concentration in fish muscle was 75 µg kg⁻¹ (wet weight), and the dietary intake of MeHg through fish consumption for Hong Kong residents was 0.37 µg kg⁻¹ week⁻¹, which was lower than the corresponding WHO limits (500 µg kg⁻¹ and 1.6 µg kg⁻¹ week⁻¹).

[Quality assurance/quality control for the determination of polycyclic aromatic hydrocarbons and phthalate esters in soils using gas chromatography-mass spectrometry].

A method for the determination of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) in soil samples by gas chromatography-mass spectrometry (GC-MS) was developed. After extracted by accelerated solvent extraction or ultrasonic extraction by dichloromethane-hexane (1:1, v/v) and dichloromethane-acetone (1:1, v/v), respectively, the extracts were cleaned up by solid phase extraction and/or gel permeation chromatography. Quality control and quality assurance procedures were carried out with the methods of whole procedure blank, blank spike recovery, clean soil matrix spike recovery, and the comparison with reference materials. The method detection limits were 0.13-2.2 microg/kg and 0.19-0.52 microg/kg and the average recoveries were 41.5%-116.9% 90.7%-107.1% for the PAHs and the PAEs, respectively. The results showed that the method can meet the technical requirements on the soil sample test and analysis in the national survey of soil pollution.

Plasma concentration of malaria parasite-derived macrophage migration inhibitory factor in uncomplicated malaria patients correlates with parasitemia and disease severity.

Host macrophage migration inhibitory factor (MIF) has been implicated in the pathogenesis of malaria infections. Several Plasmodium parasite-derived MIFs were identified to have the potential to regulate host immune response. However, the role of Plasmodium MIFs in the immunopathogenesis of malaria infection and the relationships between these mediators and inflammatory cytokines remained unclear. In this study, we have investigated two Plasmodium MIFs in peripheral blood of uncomplicated malaria patients and analyzed their correlations with several major factors during malaria infection. We found that both Plasmodium falciparum MIF (PfMIF) and Plasmodium vivax MIF (PvMIF) levels in patients were positively correlated with parasitemia, tumor necrosis factor alpha, interleukin-10 (IL-10), and monocyte chemoattractant protein 1 but were not correlated with transforming growth factor ß1 and IL-12. Of interest was that the PvMIF level was positively correlated with host body temperature and human MIF (HuMIF) concentrations. Moreover, multiple stepwise regression analysis also showed that parasitemia, IL-10, and HuMIF expression were significant predictors of Plasmodium MIF production. In addition, during antimalarial drug treatment, the decreasing of Plasmodium MIF concentrations was followed by parasitemia in most patients. Our results suggested that the Plasmodium MIF circulating level reflects the level of parasitemia and thus was closely correlated with disease severity in uncomplicated malaria. Therefore, this factor has the potential to be a promising disease predictor and is applicable in clinical diagnosis.

Enrichment of polycyclic aromatic hydrocarbons (PAHs) in mariculture sediments of Hong Kong.

Surface and core sediments collected from six fish farms in Hong Kong and from reference sites were investigated for the enrichment and sources of polycyclic aromatic hydrocarbons (PAHs). Moderately high SigmaPAH16 levels (123-947 ng g(-1), mean: 450 ng g(-1)) were found in the surface aquaculture sediments. In comparison with the sediments from the reference sites, the average enrichment percentage of total organic carbon (TOC) and PAHs in surface sediments were 21.4 and 43.8%, respectively, and in the core sediments, 24.6 and 73.7%, respectively. Mathematical source apportionment analyses (i.e. isomer ratios, hierarchical cluster analysis, principal components analysis with multiple linear regression analysis) suggested a higher percentage of petrogenic sources in aquaculture sediments. The fish feeds might be the main source of the enriched PAHs in the aquaculture sediments. To our knowledge, this is the first study showing that PAHs in aquaculture sediments could be attributed to human aquaculture activities.

Concentration and gas-particle partitioning of hexachlorobenzene in the ambient air before and after the Beijing Olympic Games.

Systematic studies of hexachlorobenzene in the ambient air before and after the Beijing Olympic Games were carried out during July 2007 to March 2009. Air samples were collected around 20th monthly on the roof of a building near the Olympic center. The average concentration of hexachlorobenzene was 264 pg x m(-3), which was higher in winter than other seasons. However, hexachlorobenzene concentration was decreased clearly in winter in 2008 compare with in 2007 due to the implementation of a series of "Green Olympic" policies. Gas-particle partitioning shows that the increase of hexachlorobenzene levels in winter time was mainly contributed by the high total suspended particulate from combustion processes such as coal-burning and traffic emission.

Characterization of PAHs in surface sediments of aquaculture farms around the Pearl River Delta.

The distribution and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of freshwater fishponds and mariculture rafts around the Pearl River Delta (PRD) were investigated. Twenty-one sample sites were chosen, consisting of fifteen freshwater fishponds and six mariculture rafts. The total PAH ( summation SigmaPAH) concentrations measured in all the sediment samples ranged from 52.7 to 717 ng g(-1), with mean of 184 ng g(-1). The marine sediment samples contained higher levels of summation SigmaPAH, high molecular weight (HMW) PAHs and carcinogenic PAHs than freshwater sediments (p<0.05). Principal component analysis/multiple linear regression analysis (PCA/MLRA) indicated that the source of PAHs in freshwater sediment was mainly derived from mixed combustion of coal, wood, and vehicle emission (66.2%). Vehicle emissions and coal combustion were the main sources (52.5 and 47.5% of summation SigmaPAH, respectively) of PAHs contaminated in the marine sediments. The present study indicated that surface sediments of freshwater fishponds and mariculture rafts around the PRD were grossly contaminated by PAHs derived from combustion sources.

Structural and functional comparison of MIF ortholog from Plasmodium yoelii with MIF from its rodent host.

Host-derived macrophage migration inhibitory factor (MIF) has been implicated in the pathogenesis of malaria infection, especially in malarial anemia. Although two Plasmodium parasite-derived MIF orthologs, Plasmodium falciparum MIF and P. berghei MIF were identified recently, the crystal structure and the precise roles of Plasmodium-derived MIFs, particularly in combination with the host MIF, remain unknown. In this study, we identified another MIF ortholog from a rodent-specific P. yoelii (PyMIF). This molecule shares a conserved three-dimensional structure with murine MIF (MmMIF), but with a different substrate binding pattern and much lower tautomerase activity. It could activate host cells via several signaling pathways in vitro, and inhibiting macrophage apoptosis, also similarly to MmMIF. However, we found that PyMIF and MmMIF acted synergistically to activate the MAPK-ERK1/2 signaling pathway at very low concentration but acted antagonistically at higher concentration. Furthermore, we detected PyMIF in the sera of infected mice and found that injection of recombinant PyMIF (rPyMIF) during infection could up-regulate several pro-inflammatory cytokines in vivo and slightly delay the death of infected mice. These data suggest that PyMIF modulates host immune responses together with host MIF and has potential to prolong parasitemia or the chronicity of malaria infection.

Epitope mapping of monoclonal antibody 1B9 against plasmodium falciparum-derived macrophage migration inhibitory factor.

A homologue of mammalian macrophage migration inhibitory factor (MIF) has been identified in Plasmodium falciparum (PfMIF). This parasite-derived cytokine and its antiserum were detected in the circulation of patients with malaria. Using a monoclonal antibody, designated mAb1B9, against PfMIF, we performed biopanning using two phage display peptide libraries to screen for the main sequence of the epitope recognized by the antibody. We then expressed a series of truncated peptides in order to identify the precise sequence of the epitope. The epitope recognized by mAb1B9 is 22 amino acids long and has the following sequence: (36)LGYIMSNYDYQKNLRFGGSNEA(57). Western analysis showed that the residues (36)LG(37) and (52)G differentiated PfMIF from the rodent malaria parasite-derived MIFs, and the residues (43)Y and (48)NL(49) differentiated PfMIF from P. vivax- and P. knowlesi-derived MIFs. The precise identification of this epitope, the first identified for PfMIF, will increase the specificity of the sandwich ELISA assays used to evaluate patients with malaria. These results indicate that mAb1B9 is useful for investigating the function of PfMIF in immune responses to malaria. Both the epitope and the monoclonal antibody against it will be valuable tools in epidemiological studies concerning this P. falciparum-derived cytokine.

Detection of Plasmodium falciparum derived macrophage migration inhibitory factor homologue in the sera of malaria patients.

Macrophage migration inhibitory factor homologues have been identified from several genera of parasites, including Plasmodium, and have shown some functional similarities to the host molecule. It was hypothesized that MIF molecules can act as a regulator in host-parasite interaction in favor of parasites survival during malaria infection. Although there has been some progress in recent studies, the biological function of the malaria parasite-derived MIF is still far from clear. In this study, cDNA of Pfmif was synthesized from mRNA of Plasmodium falciparum 3D7 strain and the recombinant protein was generated and analyzed for both enzymatic and chemotactic activities. The Plasmodium-derived MIF homologue molecules are conservative both inter-strain and interspecies. And all the sequences of them have typical structure of CC chemokine family: CC-C-C. PfMIF was proved to have chemotactic activity on human monocytes, which was similar to human-derived MIF, but at lower concentration than the latter. Meanwhile, the proline at position 2 was confirmed to be important for its tautomerase activity. With specific monoclonal and polyclonal antibodies, we demonstrated the release of PfMIF from cultured parasite-infected erythrocytes and the secretion of it from transfected eukaryotic cells in vitro, and more importantly, we found the existence of parasite derived MIF homologue in the sera of the patients infected by P. falciparum. These results will contribute to the understanding of the parasite-derived MIFs role during malaria infection.

[Cloning and expression of a homologue of human macrophage migration inhibitory factor from P. falciparum 3D7].

OBJECTIVE: To clone and express a homologue of human macrophage migration inhibitory factor (MIF) from P. falciparum 3D7--PfMIF. METHODS: The nucleotide sequence of PfMIF was found through blast P. falciparum genomic sequence databases with the amino acid sequence of human MIF (HuMIF). RT-PCR, DNA sequencing, and bioinformatics analysis were used for the cloning of Pfmif gene. The recombinant protein was expressed in E. coli and purified through the affinity column. RESULTS: The full length of Pfmif gene was cloned and sequenced. It was composed of 351 nucleotides and encoded 116 amino acids with the typical characteristic of MIF family. The recombinant protein was successfully expressed and purified. CONCLUSIONS: The Pfmif gene and recombinant protein were successfully isolated and PfMIF was preliminarily identified as a novel member of MIF family.

Immunogenicity of polyepitope libraries assembled by epitope shuffling: an approach to the development of chimeric gene vaccination against malaria.

Developing a polyepitope vaccine which contains diverse antigenic types is a promising strategy to cope with the problem of malaria variation and diversity. However, arranging the peptides to produce the most effective immunogenicity remains a hurdle. In an attempt to develop an effective complex antigenic gene vaccine, we constructed a polyepitope library by randomly assembling epitopes using the epitope shuffling technique. The polyepitope library, which contains epitopes from different antigens of Plasmodium falciparum, was divided into five sub-libraries based on the size of chimeric genes. Here we report that higher antibody titers were observed in mice with immunized with sub-libraries containing genes >1200 bp, using enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IFAT) assay to determine both individual epitope peptides and the natural parasites at the erythrocyte stage. Different levels of IgG subtypes and cytokines were elicited by different sub-library and administration times. In a rodent malaria model, some groups of immunized mice were partially cross-protected against a lethal challenge from Plasmodium yoelii. These results suggest that the immunogenicity of a polyepitope chimeric antigen is essentially conformation- and length-dependent, and demonstrates that the promising advantage of epitope shuffling technology is that it allows us to randomly assemble many polyepitope molecules in tandem format. This finding also indicates that polyepitope library vaccination is a suitable approach for screening optimized chimeric gene vaccines against malaria and other diseases.