Assessment of data sets containing a considerable number of values below the detection limits

Hecht, H.; Honikel, K. O.

doi:10.1007/bf01201592

Cited by 13 publications

(6 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When AFB 1 was not detected in certain types of food, Mi was then assumed to be LOD/2 40 . The WHO recommended an alternative method to calculate the undetected value [41][42][43] . When the undetected samplevalueswere less than 60%, the non-detected value was replaced by the value of LOD / 2.When more than 80% of the sample values were not detected, the undetected valueswere replaced by 0 or LOD, respectively, as the lower bound and upper bound.…”

mentioning

confidence: 99%

Probabilistic risk assessment of dietary exposure to aflatoxin B1 in Guangzhou, China

Zhang

Liu

Liang

et al. 2020

Sci Rep

View full text Add to dashboard Cite

Aflatoxin B 1 (AFB 1) contamination in foods is an important health challenge for low-and middle-income countries in subtropical regions. AFB 1 has been detected in a variety of foodsin Guangzhou, while the risk of dietary exposure is unknown. this study aimed to assess the probabilistic risk of dietary exposure to AFB 1 contamination in food stuffs in Guangzhou by using margin of exposure (MOE) and quantitative liver cancer risk approaches. A total of1854 AFB 1-contaminated foodstuffs were sampled in supermarkets, agricultural markets, retail shops, and family workshops from 11 districts of Guangzhou, and AFB 1 content was determined by HPLC-fluorescence detector. In total, 9.9% (184/1854) of the test samples had AFB 1 concentrations above the limit of detection. Home-made peanut oil had the highest AFB 1 concentration, with a mean value of 38.74 ± 47.45 μg kg −1. The average MOE levels of Guangzhou residents ranged from 100 to 1000. The risk of liver cancer was 0.0264 cancers (100,000 population year) −1. the health risks of suburban people were higher than those of urban people, and home-made peanut oil was the main contributorto dietary exposure to AFB 1 among suburban residents in Guangzhou. The production of home-made peanut oil should be supervised to reduce the risk of AFB 1 exposure. Aflatoxins (AFs) are mycotoxins produced by the common fungi Aspergillus flavusand Aspergillus parasiticus 1 and have been found in a wide range of crops such as maize, peanut, and walnut and their derived products 2. There are four major aflatoxins (AFB 1 , AFB2, AFG1, and AFG2) produced by the two fungi that commonly found in contaminated crops 3-5. AFB 1 and AFB 2 can be produced by A. flavus (both S and L strains) and A. parasiticus, whileAFG 1 and AFG 2 can be produced by A. flavus S strains and A. parasiticus 5,6. AFB 1 is considered the most toxic carcinogenwhich is classified as Group 1 human carcinogen by the International Agency for Research on Cancer (IARC)that induces mainly liver cancer 7-9 and to a lesser degree rectal cancer 10. AFB 1 is commonly found in cereals and nuts 11 , and it has attracted concern in lessdeveloped tropical regions 12-15. Previous studies showed that AFs were found in 5%-30%of raw peanuts and peanut products in major peanut-producing regions in China 16. Since some crops susceptible to AFs contamination, such as peanuts, are commonly consumed, it is hard to achieve zero exposure to AFs. Therefore, it is important to reduce the exposure to total AFsby establishing regulatory limits to AFs.The Codex Alimentarius Commission, the Joint Food and Agriculture Organization (FAO), and the World Health Organization (WHO) Food Standards Program jointly adopted a maximum level of 15 μg kg − 1 for total AFsin unprocessed peanuts 17. The European Commission regulation (EC) No. 1881/2006 set a maximum limit for AFB 1 of 2 μg kg −1 for peanuts and cereals that are intended for direct consumption 18. In China, the National Food Safety Standard set the limit of 20 µg kg −1 for AFB 1 in peanut and its pro...

show abstract

mentioning

confidence: 99%

Probabilistic risk assessment of dietary exposure to aflatoxin B1 in Guangzhou, China

Zhang

Liu

Liang

et al. 2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…When the 137 Cs result was lower than the DL, its value was estimated by taking half of the DL value. 22…”

Section: ■ Computation Methodsmentioning

confidence: 99%

Size Distributions of Airborne Radionuclides from the Fukushima Nuclear Accident at Several Places in Europe

Masson

Ringer

Malá

et al. 2013

Environ. Sci. Technol.

View full text Add to dashboard Cite

Segregation and radioactive analysis of aerosols according to their aerodynamic size were performed in France, Austria, the Czech Republic, Poland, Germany, and Greece after the arrival of contaminated air masses following the nuclear accident at the Fukushima Dai-ichi nuclear power plant in March 2011. On the whole and regardless of the location, the highest activity levels correspond either to the finest particle fraction or to the upper size class. Regarding anthropogenic radionuclides, the activity median aerodynamic diameter (AMAD) ranged between 0.25 and 0.71 μm for (137)Cs, from 0.17 to 0.69 μm for (134)Cs, and from 0.30 to 0.53 μm for (131)I, thus in the "accumulation mode" of the ambient aerosol (0.1-1 μm). AMAD obtained for the naturally occurring radionuclides (7)Be and (210)Pb ranged from 0.20 to 0.53 μm and 0.29 to 0.52 μm, respectively. Regarding spatial variations, AMADs did not show large differences from place to place compared with what was observed concerning bulk airborne levels registered on the European scale. When air masses arrived in Europe, AMADs for (131)I were about half those for cesium isotopes. Higher AMAD for cesium probably results from higher AMAD observed at the early stage of the accident in Japan. Lower AMAD for (131)I can be explained by the adsorption of gaseous iodine on particles of all sizes met during transport, especially for small particles. Additionally, weathering conditions (rain) encountered during transport and in Europe in March and April contributed to the equilibrium of the gaseous to total (131)I ratio. AMAD slightly increased with time for (131)I whereas a clear decreasing trend was observed with the AMADs for (137)Cs and (134)Cs. On average, the associated geometric standard deviation (GSD) appeared to be higher for iodine than for cesium isotopes. These statements also bear out a gaseous (131)I transfer on ambient particles of a broad size range during transport. Highest weighted activity levels were found on the 0.49-0.95 μm and on the 0.18-0.36 μm size ranges in France and in Poland, respectively. The contribution from resuspension of old deposited (137)Cs was assessed for the coarse particle fractions only for the first sampling week.

show abstract

“…Produce two estimates using 0 and LOD for all the results less than LOD a,d Use methods in (Vlachonikolis and Marriott, 1995;Hecht and Honikel, 1995) and/or graphical methods b,c . Use with caution if total number of measurements is <100.…”

Section: Existing Guidelines For Handling Non-detectsmentioning

confidence: 99%

“…This is particularly true when a large percentage of the results are below the LOQ and the recommendations given in Table 1 reflect the assumption that such "quantified data" will be available down to the LOD. Use methods in (Vlachonikolis and Marriott, 1995;Hecht and Honikel, 1995) and/or graphical methods b,c > 60 but 80% non-quantified and with at least 25 results quantified.…”

Section: Existing Guidelines For Handling Non-detectsmentioning

confidence: 99%

Management of left‐censored data in dietary exposure assessment of chemical substances

2010

EFS2

233

View full text Add to dashboard Cite

Within the general framework of chemical risk assessment, a difficult step in dietary exposure assessment is the handling of concentration data reported to be below the limit of detection (LOD). These data are known as nondetects and the resulting distribution of occurrence values is left-censored. Handling left-censored data represents a challenge for EFSA"s collection and statistical analysis of chemical occurrence data. EFSA has so far treated left-censored data with widely used substitution methods recommended by international organisations. The appropriateness of this approach has a natural limitation in the computation of percentiles and in the application of statistical techniques. An EFSA working group was established to estimate the accuracy of methods currently used and to propose recommendations for more advanced alternative statistical approaches. Based on a simulation study and on analyses of real data, an ad hoc evaluation was carried out to assess the performance of different statistical methods to handle non-detects, i.e. parametric Maximum likelihood (ML) models, the log-probit regression method and the non-parametric Kaplan-Meier (KM) method. Results showed that the number of samples had a relatively limited impact on the accuracy and precision of estimates, but the degree of censoring had a large effect. When analysing a complex set of data, it was also shown that it is essential to identify possible sources of heterogeneity in a dataset, such as country of sample collection/origin, food group, laboratory, etc. Statistical analyses should either be conducted separately from these factors, or, to explicitly account for this heterogeneity, fixed/random effect ML models could be used. Based on a minimum number of available samples and to different values of censoring percentages, the working group outlined recommendations, including the use of appropriate statistical tests, to handle left-censored distributions of chemical contaminant data in the context of exposure assessment.

show abstract

Assessment of data sets containing a considerable number of values below the detection limits

Cited by 13 publications

References 1 publication

Probabilistic risk assessment of dietary exposure to aflatoxin B1 in Guangzhou, China

Probabilistic risk assessment of dietary exposure to aflatoxin B1 in Guangzhou, China

Size Distributions of Airborne Radionuclides from the Fukushima Nuclear Accident at Several Places in Europe

Management of left‐censored data in dietary exposure assessment of chemical substances

Contact Info

Product

Resources

About