A Method for Evaluating Exposure to Nitrous Oxides by Application of Lognormal Distribution
A Method for Evaluating Exposure to Nitrous Oxides by Application of Lognormal Distribution: S.S. Borjanovic, et al. Department of Work Physiology, Institute of Occupational Health “Dr Dragomir Karajovic”—A lognormal distribution adequately describes exposure to nitrous oxides in a work environment. The aim of this paper was to assign to the measured data a certain degree of variability which defines the interval in which real concentrations can be found with a given probability. Exposures may be evaluated by using estimates of the geometric mean (GM) and the geometric standard deviation (GSD), i.e. central value and dispersion index, to calculate the confidence interval (Cl) around the mean exposure and compare this interval to the occupational exposure limit. The concentration of nitrous oxides (114 random temporal measurements covering all three shifts, during 6 consecutive days) on coated electrode welding in a car manufacturing plant, was determined with colourimetric direct reading method. Statistical analysis (chi‐square and Kolmogorov‐Smirnov goodness of fit tests, lognormal and Gaussian distribution fitting and Q‐G plots) was performed. The distribution of the nitrous oxides concentration in the work environment studied closely resembled that of lognormal distribution. The geometric mean was 4.098 mg/m3, median 4.00 mg/m3, geometric standard deviation 1.829 and 95% confidence interval 3.66‐4.58 mg/m3. It is possible to apply the computed GSD for evaluation of exposure limits to nitrous oxides in any other work environment, even with only a few measurements.
Evaluation of the effect of governmental control of human exposure to two phthalates in Japan using a urinary biomarker approach.
In Japan, the use of certain phthalates has been regulated. We analyzed the effectiveness of these measures using an analytical biomarker approach. We measured two phthalate metabolites, mono-n-butyl phthalate (MBP) and mono-2-ethylhexyl phthalate (MEHP) in urine samples from 36 participants using enzymatic deconjugation, offline solid phase extraction, and HPLC-ESI-MS/MS. From the levels measured and individual values of creatinine excretion rate the daily intake was determined and compared to each corresponding tolerable daily intake (TDI). The levels of urinary MBP and MEHP were < 1.8-280 and 0.76-25 microg/l, respectively. The ranges of the estimated daily intake of di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) from 35 adult urine samples were 0.22-4.5 and 0.37-7.3 microg/kg/ day, respectively. These values were lower than the corresponding TDIs. After comparing these values to previous exposure assessment data on DEHP in Japan, it could be seen that the DEHP intake dropped over the period from 1998 to 2001. Children were not covered in the present study, so the results may only be applicable to adults, not to the Japanese population at large. Even so, the small number of people in one specific geographic area cannot be considered representative of the adult Japanese population. In addition to MEHP, the secondary metabolites of DEHP, which are more suitable biomarkers should be measured in the future.
The incidence of dead and dying fish in the Moray Firth, September 1963
Dead and dying fish were reported from the Moray Firth during a period of 15 days in September 1963. The initial mortalities were in the inner Firth, but they later spread outwards, especially eastwards along the southern shores of the Firth. Mass mortalities of the lugworm (Arenicola marina) also occurred in Scottish waters in 1962 and 1963, and at Balintorein Easter Ross fish and lugworm mortalities were contemporary.