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Objective: The current meta-analysis evaluated the association between vitamin B 12 intake and blood vitamin B 12 level and colorectal cancer (CRC) risk. Design: The PubMed and EMBASE databases were searched. A dose-response analysis was performed with generalized least squares regression, with the relative risk (RR) and 95 % CI as effect values. Setting: The meta-analysis included seventeen studies. Subjects: A total of 10 601 patients. Results: The non-linear dose-response relationship between total vitamin B 12 intake and CRC risk was insignificant (P = 0·690), but the relationship between dietary vitamin B 12 intake and CRC risk was significant (P < 0·001). Every 4·5 μg/d increment in total and dietary vitamin B 12 intake was inversely associated with CRC risk (total intake: RR = 0·963; 95 % CI 0·928, 0·999; dietary intake: RR = 0·914; 95 % CI 0·856, 0·977). The inverse association between vitamin B 12 intake and CRC risk was also significant when vitamin B 12 intake was over a dosage threshold, enhancing the non-linear relationship. The non-linear dose-response relationship between blood vitamin B 12 level and CRC risk was insignificant (P = 0·219). There was an insignificant association between every 150 pmol/l increment in blood vitamin B 12 level and CRC risk (RR = 1·023; 95 % CI 0·881, 1·187). Conclusions: Our meta-analysis indicates that evidence supports the use of vitamin B 12 for cancer prevention, especially among populations with high-dose vitamin B 12 intake, and that the association between CRC risk and total vitamin B 12 intake is stronger than between CRC risk and dietary vitamin B 12 intake only.

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Increasing discharge of sewage sludge is a threat to the ecological environment, and sludge treatment via combustion is the most feasible alternative. However, the low calorific value and high-water content of raw sludge results in poor firing performance and increases the risk of environmental pollution. Recently, co-combustion has emerged as a more environment-friendly technology. Herein, the combustion behaviours of sewage sludge, corn stalk and their mixture at four heating rates were studied via thermogravimetric experiments. Results yielded the division of weight loss into three stages for corn stalk: dehydration, combustion of volatiles and combustion of fixed carbon; four stages were identified for sewage sludge and the mixture of sludge and stalk: dehydration, combustion of volatiles, combustion of fixed carbon and thermal decomposition of a small amount of minerals. Synergistic analyses found that with a 60% blending ratio of sewage sludge, interaction between the components in the high-temperature range was greatly promoted. Gas emission characteristics showed that CO 2 was the main product during (co-)combustion, while the NO x emissions at low (or high) temperatures for the blend were higher (or lower) than the theoretical values. Temperature had little effect on H 2 S emissions, though it significantly affected SO 2 emissions during co-combustion. V CS gas emissions when CS is burned SS E 60% actual amounts of released gas with sludge blending ratios of 60% SS C 60% theoretical amounts of released gas with sludge blending ratios of 60%