Aspergillus Section Flavi and aflatoxins in dusts generated by agricultural processing facilities in the Philippines

Relatively few data exist regarding concentrations of aflatoxins and their causative organisms in dusts within occupational environments. Here, we examined Aspergillus Section Flavi populations and aflatoxin levels in 54 samples of dusts generated by agricultural processing facilities as possible indicators of aflatoxin exposure in the Philippines. The average incidence of Aspergillus Section Flavi expressed as a percentage of total mould populations in rice dust, corn dust, feed dust and copra dust were 8, 4, 31 and 10%, respectively. Predominant aflatoxigenic fungi isolated were Aspergillus flavus and A. parasiticus with ratios of 31:1, 40:5, 16:4 and 1:1 in rice dust, corn dust, feed dust and copra dust, respectively. Aflatoxins produced by selected isolates in in vitro rice culture ranged from 100 µg kg^?1 to 100.5 mg kg^?1. Toxigenicity of isolates based on the average aflatoxin concentrations produced by positive isolates were in the order of copra dust > corn dust > rice dust > feed dust. Average natural concentrations of aflatoxins in rice dust, corn dust, feed dust, and copra dust were 25, 6, 15 and 10 µg kg^?1, respectively. Estimates of the amount of inhaled aflatoxins by workers in an 8‐h work shift ranged from 0.06 to 114 ng, the average of which is higher than the amount of aflatoxins ingested by Filipinos due to the consumption of polished rice. The presence of highly toxigenic Aspergillus Section Flavi and aflatoxins in agricultural dust is a critical health risk for workers, considering the frequency of exposure and the possibility of inhalation and subsequent absorption of aflatoxins in the respiratory tract. Copyright © 2006 Society of Chemical Industry     

Production of alternaria mycotoxins by Alternaria alternata isolated from weather-damaged wheat

The production of Alternaria mycotoxins by Alternaria alternata isolated from Chinese weathered wheat kernels were first investigated on polished rice and durum wheat grains. These mycotoxins included alternariol (AOH) and its monomethyl ether (AME), altenuene (ALT), altertoxin I (ATX-I), and tenuazonic acid (TA). Of 25 isolates tested, all were AOH and AME producers, 21 (84%) coproduced ALT and ATX-I, and 8 (32%) produced TA in rice culture. TA was the most abundant toxin produced at a level ranging from 1,369 to 3,563 mg/kg. Much smaller amounts of AOH, AME, ALT, and ATX-I were present with average concentrations of 54, 40, 44, and 8 mg/kg, respectively. There were linear correlations between the level of AOH and AME (r = 0.846), alternariols (AOH plus AME) and ALT (r = 0.785), and ATX-I and TA (r = 0.553). Polished rice medium seems to support a bit more production of Alternaria metabolites than wheat but with an insignificant difference in concentrations (P > 0.05). A study of the time-course of toxin production by A. alternata isolates indicated that AOH production began faster than any other toxins monitored, and ALT production exhibited a progressive increase throughout the experiment. TA producers might reveal their considerably higher ability to produce toxin in the field despite their low frequency.     

Effects of heating procedures on deoxynivalenol, nivalenol and zearalenone levels in naturally contaminated barley and wheat.

The influence of heating temperature and time on deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEA) contents in naturally co-contaminated barley and wheat was investigated intending to establish the basis for a decontamination model of Fusarium mycotoxins in cereals. The standard toxins and whole barley powder samples were heated in a convection oven at 140, 160, 180, 200, or 220 degrees C, and kernel subsamples (200 g each) were roasted in an experimental rotary gas-fired roaster at 150, 180 or 220 degrees C. All treatments resulted in a time-temperature-dependent decomposition of the toxins; the logarithm of the toxin remaining % presented a linear relationship with heating time. The lines equations were used to estimate the half (H) and decimal (D) decomposition times (time required to destroy 50 or 90% of the toxin, respectively). DON and NIV H and D decomposition times were similar and 50% shorter for heated standards than for whole barley powder. ZEA standard values were considerably longer, while whole barley powder values were comparable with those of DON and NIV. At 220 degrees C, D decomposition times of DON, NIV and ZEA heated standards were 11, 10 and 85 min, respectively, while the values obtained in whole barley powder were the same for the three toxins (25 min). The determination of H and D decomposition values constitutes a basis to understand the heating stability nature of each toxin.     

Neutron spectra and angular distributions of concrete-moderated neutron calibration fields at JAERI

The Facility of Radiation Standards of Japan Atomic Energy Research Institute has been equipped with concrete-moderated neutron calibration fields as simulated workplace neutron fields. The fields use an 241Am-Be neutron source placed in the narrow space surrounded by concrete bricks, walls and floor. The neutron spectra and the neutron fluence rates of the fields were measured with the Bonner multi-sphere spectrometer system (BMS), spherical recoil-proton proportional counters, and a liquid scintillation counter (NE-213). The results were compared with each other. The reference values of H*(10) were determined from the results of BMS. The angular distributions of neutron fluence were calculated using MCNP-4B2 to obtain the reference values of Hp(10). The calculated results show that the scattered neutrons have a wide range of incident angles. The reference Hp(10) values considered the angular distribution were found to be 10-18% smaller than those without consideration.