Estimation of the benchmark dose of urinary cadmium as the reference level for renal dysfunction: a large sample study in five cadmium polluted areas in China.

BACKGROUND: Itai-itai disease primarily results from cadmium (Cd) exposure and is known as one of the four major pollution diseases in Japan. Cd pollution is more serious in several areas of China than in Japan. However, there is still a lack of information regarding the threshold level of Cd exposure for the adverse health effects in the general Chinese population. This study aims to evaluate the reference value of urinary Cd (UCd) for renal dysfunction in a Chinese population as the benchmark dose lower confidence limit (BMDL) based on a large sample survey. METHODS: A total of 6103 participants who lived in five Cd polluted areas of China participated in this study. We analyzed UCd levels as a biomarker of exposure and urinary ß2-microglobulin (Uß2-MG) levels as a renal tubular effect biomarker. The BMD studies were performed using BMD software. The benchmark response (BMR) was defined as a 10% additional risk above the background. RESULTS: There was a positive correlation between the UCd levels and the prevalence of Uß2-MG. The BMD of UCd for Uß2-MG was estimated for each province. The findings showed that the BMD levels were related to the participants' geographic region, which may be partially due to the large differences in Cd exposure level, ethnic group, lifestyle and diet of the sample population in these study areas. The reference level of UCd for the renal effects was further evaluated by combining the five sets of data from all 6103 subjects. The overall BMDLs of UCd for Uß2-MG with an excess risk of 10% were 2.00 µg/g creatinine (µg/g cr) in males and 1.69 µg/g cr in females, which were significantly lower than the World Health Organization (WHO) threshold level of 5 µg/g cr for Cd-related renal effects. CONCLUSIONS: The selection of the sample population and geographic region affected the BMDL evaluation. Based on the findings of this survey of a large sample population, the UCd BMDLs for Uß2-MG in males with BMRs at 10% were 2.00 µg/g cr. The BMD was slightly lower in females, which indicated that females may be relatively more sensitive to Cd exposure than males.

Benchmark Dose Estimation for Cadmium-Induced Renal Effects Based on a Large Sample Population from Five Chinese Provinces.

A survey involving 6103 participants from five Chinese provinces was conducted to evaluate the threshold value of urinary cadmium (UCd) for renal dysfunction as benchmark dose low (BMDL). The urinary N-acetyl-ß-D-glucosaminidase (UNAG) was chosen as an effect biomarker. The UCd BMDLs for UNAG ranged from 2.18 µg/g creatinine (cr) to 4.26 µg/g cr in the populations of different provinces. The selection of the sample population and area affect the evaluation of the BMDL. The reference level of UCd for renal effects was further evaluated based on the data of all 6103 subjects. With benchmark responses (BMR) of 10%/5%, the overall UCd BMDLs for males in the total population were 3.73/2.08 µg/g cr. The BMD was slightly lower in females, thereby indicating that females may be relatively more sensitive to Cd exposure than are males.

Cadmium contamination of rice from various polluted areas of China and its potential risks to human health.

A total of 484 rice samples were collected from five polluted areas in China to investigate the cadmium (Cd) contamination of rice and its potential health risks. The mean Cd contents of analyzed rice samples obtained from different areas ranged from 0.149 to 0.189 mg·kg(-1). Cd concentrations in more than 18% of rice samples exceeded the maximum allowable Cd concentration, and the highest level of 41.1% was observed in samples from Hezhang, Guizhou, which was characterized by serious Cd pollution. Target hazard quotient (THQ) values of 1.5 to 7.8 from rice intake indicated a significant non-carcinogenic health risk for humans, particularly for highly exposed consumers. Children are more at risk than adults, as indicated by the higher THQs. Moreover, carcinogenic risks of Cd from rice intake for average and high consumers in the selected areas were two to three and four to eight greater, respectively, than the threshold value recommended by the International Commission on Radiological Protection.

Body burden of cadmium and its related factors: a large-scale survey in China.

A survey of more than 6000 participants from four distinct non-polluted and polluted regions in China was conducted to evaluate the body burden of cadmium (Cd) on the Chinese populations using urinary Cd (UCd) as a biomarker. The findings revealed that the UCd level was 1.24 µg/g creatinine (µg/g cr) for the sample population from non-polluted Shanghai, and the UCd levels exceeded 5 µg/g cr, which is the health-based exposure limit set by the World Health Organization (WHO), in 1.1% of people. The mean UCd levels in moderately polluted (Hubei and Liaoning) and highly polluted areas (Guizhou) were 4.69 µg/g cr, 3.62 µg/g cr and 6.08 µg/g cr, respectively, and these levels were 2.9 to 4.9 times the levels observed in Shanghai. Notably, the UCd levels exceeded the recently updated human biomonitoring II values (i.e., intervention or "action level") in 44.8%-87.9% of people from these areas compared to only 5.1%-21.4% of people in Shanghai. The corresponding prevalence of elevated UCd levels (>WHO threshold, 5 µg/g cr) was also significantly higher (30.7% to 63.8% vs. 1.1%), which indicates that elevated Cd-induced health risks to residents in these areas. Age and region were significant determinants for UCd levels in a population, whereas gender did not significantly influence UCd.

Coproduction of hydrogen and methane via anaerobic fermentation of cornstalk waste in continuous stirred tank reactor integrated with up-flow anaerobic sludge bed.

A 10 L continuous stirred tank reactor (CSTR) system was developed for a two-stage hydrogen fermentation process with an integrated alkaline treatment. The maximum hydrogen production rate reached 218.5 mL/L h at a cornstalk concentration of 30 g/L, and the total hydrogen yield and volumetric hydrogen production rate reached 58.0 mL/g-cornstalk and 0.55-0.57 L/L d, respectively. A 10 L up-flow anaerobic sludge bed (UASB) was used for continuous methane fermentation of the effluents obtained from the two-stage hydrogen fermentation. At the optimal organic loading rate of 15.0 g-COD/Ld, the COD removal efficiency and volumetric biogas production rate reached 83.3% and 4.6L/Ld, respectively. Total methane yield reached 200.9 mL/g-cornstalk in anaerobic fermentation with the effluents and alkaline hydrolysate. As a result, the total energy recovery by coproduction of hydrogen and methane with anaerobic fermentation of cornstalk reached 67.1%.

Enhanced coproduction of hydrogen and methane from cornstalks by a three-stage anaerobic fermentation process integrated with alkaline hydrolysis.

A three-stage anaerobic fermentation process including H(2) fermentation I, H(2) fermentation II, methane fermentation was developed for the coproduction of hydrogen and methane from cornstalks. Hydrogen production from cornstalks using direct microbial conversion by Clostridium thermocellum 7072 was markedly enhanced in the two-stage thermophilic hydrogen fermentation process integrated with alkaline treatment. The highest total hydrogen yield from cornstalks in the two-stage fermentation process reached 74.4 mL/g-cornstalk. The hydrogen fermentation effluents and alkaline hydrolyzate were further used for methane fermentation by anaerobic granular sludge, and the total methane yield reached 205.8 mL/g-cornstalk. The total energy recovery in the three-stage anaerobic fermentation process integrated with alkaline hydrolysis reached 70.0%.

Enhancement of phenylethanoid glycosides biosynthesis in cell cultures of Cistanche deserticola by osmotic stress.

The effect of osmotic stress on cell growth and phenylethanoid glycosides (PeGs) biosynthesis was investigated in cell suspension cultures of Cistanche deserticola Y. C. Ma, a desert medicinal plant grown in west region of China. Various initial sucrose concentrations significantly affected cell growth and PeGs biosynthesis in the suspension cultures, and the highest dry weight and PeGs accumulation reached 15.9 g l(-1)-DW and 20.7 mg g(-1)-DW respectively at the initial osmotic stress of 300 mOsm kg(-1) where the sucrose concentration was 175.3 mM. Stoichiometric analysis with different combinations of sucrose and non-metabolic sugar (mannitol) or non-sugar osmotic agents (PEG and NaCl) revealed that osmotic stress itself was an important factor for enhancing PeGs biosynthesis in cell suspension cultures of C. deserticola. The maximum PeGs contents of 26.9 and 23.8 mg g(-1)-DW were obtained after 21 days at the combinations of 87.6 mM sucrose with 164.7 mM mannitol (303 mOsm kg(-1)) or 20 mM PEG respectively, which was higher than that of C. deserticola cell cultures grown under an initial sucrose concentration of 175.3 mM after 30 days. The stimulated PeGs accumulation in the cell suspension cultures was correlated to the increase of phenylalanine ammonium lyase (PAL) activity induced by osmotic stress.

Improvement of phenylethanoid glycosides biosynthesis in Cistanche deserticola cell suspension cultures by chitosan elicitor.

Effect of chitosan elicitor on growth and phenylethanoid glycosides (PeGs) accumulation in Cistanche deserticola cell suspension cultures was investigated. PeGs accumulation was dramatically improved by addition of selected chitosan at optimal elicitation conditions. Furthermore, a strategy of repeated addition of the chitosan elicitor for enhancing PeGs accumulation was developed. The chitosan elicitor of 10 mg l(-1)-medium repeatedly added on days 15 and 17 improved PeGs accumulation further, and the final PeGs production in the treated cell cultures of C. deserticola reached 364.6 mg l(-1), which was 3.4-fold higher than that of the control without elicitation. The increase of PeGs accumulation in C. deserticola cell suspension cultures was related to the increase of phenylalanine ammonium lyase activity stimulated by the chitosan elicitor.