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Objective: To investigate the characteristics, temporal trend of silicosis, and provide basis for risk assessment and precise prevention and control of occupational diseases. Methods: Using descriptive statistics to analyze the reported cases of silicosis by SPSS 20.0 software. Reported silicosis cases, the constituent ratio, the incidence age and the working age at onset were analyzed by a linear trend test. Analyzing the variation trends of regional, industry, economic type and enterprise scale distributions by the chi-square trend test. Moreover, using Moran's I method for spatial autocorrelation analysis and trend-surface analysis. Results: (1) During 2006 to 2015, Guangdong province had reported 1, 428 cases of silicosis, mainly gathered in Foshan, Zhongshan, Guangzhou, Shenzhen, which included 1391 male cases accounting for 97.41%. And the average incidence age was 45 (39, 51) . The average working age of onset was 9 (5.5, 15) . In economic type distribution, the private economy took the main part, accounting for 59.1%. In enterprise scale distribution, it was dominated by small and medium enterprises (SMEs) , accounting for 32.4% and 37.3% respectively. In industry distribution, most cases were gathered in materials and mining industry, accounting for 32.1% and 22.9% respectively. (2) The number of silicosis cases, the incidence age and the working age of onset showed a rising trend ( P <0.01) . Meanwhile, the constituent ratios of medium-sized enterprises and building materials industry were increasing ( P <0.05) . The annual variation trends of regional, economic type and age distributions were not statistically significant ( P > 0.05) . (3) The spatial distribution trend showed an inverted U type, which was firstly raised and then declined from south to north and from east to west. The distribution characteristic demonstrated some high-high cluster areas, including Chancheng, Nanhai, Shunde, Panyu, Dongguan, Pengjiang, and Zhongshan. While Wuhua showed a high-low outlier form ( P <0.01) . Conclusion: Silicosis cases, age and working age of onset were on the rise, as well as the industry and enterprise scale distributions of occupational diseases presented a certain trend in Guangdong province from 2006 to 2015. There were high-high cluster and high-low outlier phenomena in spatial distribution with spatial correlation. Therefore, our work of silicosis epidemic trend and distribution may provide some bases for the occupational disease risk assessment and control.

The rapidly expanding mariculture and commercial region along the southern coast of China has experienced sporadic outbreaks of paralytic shellfish poisoning for nearly 30 years, yet virtually nothing is known of the nature of that toxicity or of the causative organisms. This study presents the first direct comparisons of the high performance liquid chromatography toxin composition profiles of shellfish implicated in paralytic shellfish poisoning outbreaks in Daya Bay with Alexandrium tamarense cultures established from those waters. The three cultures that were analyzed produced an unusually high proportion of the low potency N-sulfocarbamoyl toxins C1 and C2 (nearly 90% of the total), and only trace quantities of the other saxitoxin derivatives. Total toxicity was thus very low with mild acid extraction, ranging between 7.2 and 12.7 fmole cell-1, or 0.7-0.9 pg saxitoxin equiv. cell-1. Following acid hydrolysis using the standard AOAC extraction method, the dominant toxins in the cultures were gonyautoxins 2 and 3 and decarbamoyl gonyautoxins 2 and 3. Total potency increased fourfold to 2.6-3.4 pg saxitoxin equiv. cell-1 following acid hydrolysis. These cultures are thus at the low end of the range of toxicities recorded for members of the A. tamarense species complex. Two scallop samples and one mussel sample collected from Daya Bay during paralytic shellfish poisoning episodes in 1990 and 1991 were also analyzed following the AOAC extraction procedure. The toxin profiles were similar for the three shellfish samples, in that the same suite of toxins were present in each, but the relative proportion of those toxins varied. The dominant toxins were gonyautoxins 2 and 3 and toxins C1-C4. Total toxicity was 336 and 654 micrograms saxitoxin per 100 g meat for the scallop samples, and 723 for the mussels. Toxins C3,4 were present in the shellfish at up to 22 mole%, but were not detected in cultures, even when mild acid was used for extraction. Despite the otherwise similar nature of the culture versus the shellfish toxin signatures, the presence of C3,4 indicates that another strain or species of Alexandrium, or possibly a paralytic shellfish poisoning-producing species of another genus was responsible for the 1990 and 1991 paralytic shellfish poisoning outbreaks in Daya Bay. Since the cultures analyzed were of low intrinsic toxicity, A. tamarense may be more widespread along the south coast of China than is suggested by the sporadic pattern of past paralytic shellfish poisoning outbreaks. Blooms with high cell density are required to generate sufficient toxin to be dangerous. The alarming increase in algal blooms in Chinese waters due to persistent and growing pollution may make these low toxicity populations more problematic in the future.