Estimation of exposure to food packaging materials. 1: Development of a food-packaging database

A food-packaging database was developed to provide qualitative information on the types of packaging materials used for foods. Packaging information was collected from a sample of 594 children aged 5-12 years as part of a national children's food survey carried out in Ireland during 2003-04. All the food packaging collected during the survey was forwarded to the coordinating centre for further analysis and entry into the Irish Food Packaging Database. The database was created in Microsoft Access® and stored information on: the brand of the food, the packaging type, the unit weight, the contact layer, the European Union food type (i.e. aqueous, acidic, alcoholic or fatty) and other relevant parameters. Of the 5551 different brand foods consumed by children in the food survey, packaging information was collected on 3441 (62%). As some brand foods had different unit weights and packaging formats, there was duplication of some brand foods in the database to account for this fact. Therefore, there were 3672 packaging entries in the database. Of these, plastics were the most common packaging contact layer (n = 2874, 78.3%). Multimaterial multilayers with a plastic contact layer accounted for 459 (12.5%) entries. Polyethylene was the most frequently used contact layer (n = 941), with polypropylene a close second (n = 809). This database is unique in Europe for the quality and amount of food packaging information it contains and could be used to develop packaging use factors for a more refined exposure assessment to food packaging materials in the European Union.     

A review of dietary exposure and toxicological information on epoxidised soybean oil (ESBO) in food-contact applications

ABSTRACT

Plasticisers have a long history of use in the industrial manufacture and processing of polymers for the purpose of increasing the flexibility and strength of the material. Approximately, 80–90% of the plasticiser market is devoted to the production of PVC, a highly versatile thermoplastic used to produce both rigid and flexible articles. Many types of plasticisers, including ortho-phthalate esters (OPE), can be added to PVC to impart flexibility. Recently, alternatives to OPEs, such as epoxy esters and aliphatic adipates, are becoming more prevalent for use in PVC-based food-contact articles. Epoxidised soybean oil (ESBO) is used as a plasticiser in flexible PVC for many food-contact articles, including food packaging and food processing equipment, from which it can potentially migrate into food and become a component of an individual’s daily diet. The purpose of this review is to provide an update on the US dietary exposure and toxicological information on ESBO used in PVC-based food-contact articles. The cumulative dietary concentration (CDC) and cumulative estimated daily intake (CEDI) for ESBO from its use as a plasticiser in PVC-based food-contact articles (i.e. gaskets for glass jar lids and film wraps) was calculated to be 2.6 mg/kg (i.e. ppm) and 0.13 mg/kg bw/d, respectively, for the general population. Some regulatory agencies have reported safety levels for ESBO, and the most conservative no observed adverse effect level (NOAEL) was identified to be 100 mg/kg bw/d (i.e. 2000 ppm) based on a two-year feeding study in rats. The current CEDI is well below these levels, supporting the safe use of ESBO in food-contact applications.     

Consumer exposure to substances in plastic packaging. I. Assessment of the contribution of styrene from yogurt pots

A generic methodology for the assessment of consumer exposure to substances migrating from packaging materials into foodstuffs during storage is presented. Consumer exposure at the level of individual households is derived from the probabilistic modeling of the contamination of all packed food product units (e.g. yogurt pot, milk bottle, etc.) consumed by a given household over 1 year. Exposure of a given population is estimated by gathering the exposure distributions of individual households to suitable weights (conveniently, household sizes). Calculations are made by combining (i) an efficient resolution of migration models and (ii) a methodology utilizing different sources of uncertainty and variability. The full procedure was applied to the assessment of consumer exposure to styrene from yogurt pots based on yearly purchase data of more than 5400 households in France (about 2 million yogurt pots) and an initial concentration c₀ of styrene in yogurt pot walls, which is assumed to be normally distributed with an average value of 500 mg kg^-1 and a standard deviation of 150 mg kg^-1. Results are discussed regarding both sensitivity of the migration model to boundary conditions and household practices. By assuming a partition coefficient of 1 and a Biot number of 100, the estimated median household exposure to styrene ranged between 1 and 35 µg day^-1 person^-1 (5th and 95th percentiles) with a likely value of 12 µg day^-1 person^-1 (50th percentile). It was found that exposure does not vary independently with the average consumption rate and contact times. Thus, falsely assuming a uniform contact time equal to the sell-by-date for all yogurts overestimates significantly the daily exposure (5th and 95th percentiles of 2 and 110 µg day^-1 person^-1, respectively) since high consumers showed quicker turnover of stock.     

Dietary exposure to chemical migrants from food contact materials: A probabilistic approach

A two-dimensional probabilistic model has been developed to estimate the short-term dietary exposure of UK consumers to migrants from food packaging materials. The current EU approach uses a default scenario of assuming that all individuals are 60 kg weight and consume 1 kg of food packaged in the material of interest per day. Using four UK National Dietary and Nutrition Surveys comprising 4-7 day dietary records for different age groups and survey years, a sample representative of the UK population has been obtained consuming around 4200 different food items. Each survey provides records for around 2000 individuals and supplies detailed information on the consumption of food and data on sex, height and socio-economic status which may be used to analyse the exposure of selected groups within the community. As a result we are able to address the variation in consumption of food amongst individuals, and account for actual body weights providing a more accurate representation of the 'true' exposure. The migrants bisphenol A diglycidyl ether (BADGE), di-2-ethylhexyl adipate (DEHA) and styrene were considered as specimen compounds although the methodology employed has the flexibility to adapt to other migrants and packaging types and indeed other food contaminants. Exposure for each individual is estimated by calculating and summing the individual exposure from each item in their diet, and is repeated for all individuals in each survey to produce a distribution of exposures for the population. The packaging type of each food item is assigned by utilizing known packaging types from the database or, by sampling from a distribution based upon market share information. The parameters contributing towards the exposure from a packaged dietary item are migrant concentration and item weight. Distributions are used to represent the inherent variation and uncertainty affecting these parameters. Where data on concentrations for a particular type of food are lacking, expert judgement is used to extrapolate from available data for other food types. The model can also be run using only migration data for food simulants. In this case, concentrations expected for each of the food items are assigned based on the data for the relevant food simulant. The primary outputs of the model are distributions of estimated daily intakes for the selected population. Each distribution gives the variation across the population subject to the uncertain parameters sampled in that iteration of the model. Analysing the ensemble of distributions allows us to obtain the confidence limits around estimates for percentiles due to the uncertainties. The probabilistic approach allows sensitivity analysis to evaluate the relative importance of the input parameters and places confidence bounds on the outputs to show the effect of the uncertainties and the contribution of each food type toward the overall exposure.     

Consumer exposure to phthalates from paper packaging: an integrated approach

This paper presents an integrated approach to estimate the exposure of the Portuguese population to phthalates as a contaminant originating from paperboard packaging. The approach combined data of migrant concentration in the foods resulting from a stochastic simulation with consumption data of food packaged in paperboard. The results from the exposure model were validated with experimental values actually found in the food. A short surveillance exercise was conducted with samples collection from market shelves to identify and quantify the phthalates present in both the packages and the food. The distribution of values for the di-butyl phthalate concentration in the packages was used as the input of the initial concentration in the Weibull model to estimate the concentration of this phthalate in the foods. This distribution of occurrence data was then combined with the packaging usage data in a probabilistic simulation with a Monte Carlo sampling method. Exposure values ranged between zero and 8.95 µg day^?1 kg_bw, a value close to the tolerable daily intake established by the European Food Safety Authority (EFSA)–10 µg day^?1 kg_bw. However, the 97.5th percentile and the average were 1.82 and 0.44 day^?1 kg_bw, respectively, indicating that further refinement of the estimates is not necessary. Other phthalates were also detected in the packaging samples: di-isobutyl phthalate and di-ethylhexyl phthalate. The latter was present in all packaging samples collected and was detected in a few food samples at values requiring further investigation.     

Use and impact of usual intake models on dietary exposure estimate and risk assessment of chemical substances: a practical example for cadmium,acrylamide and sulphites

To estimate of food and nutrient intakes, 24-h recalls are frequently used in dietary assessment. However intake data collected for a short period are a limited estimator of long-term usual intake. An important limitation of such data is that the within-person variability tends to inflate the intake distribution leading to a biased estimation of extreme percentiles. Statistical models, named usual-intake models, that separate the within-person variability from the between-persons variability, have lately been implemented. The main objectives of this study were to highlight the potential impact that usual-intake models can have on exposure estimate and risk assessment and to point out which are the key aspects to be considered in order to run these models properly and be sure to interpret the output correctly. To achieve the goal we used the consumption data obtained by the French dietary survey INCA2 and the concentration data collected during the French TDS2, using Monte Carlo Risk Assessment (MCRA) software, release 8.0. For the three substances included in this study (cadmium, acrylamide and sulphites), the exposure of the upper percentiles was significantly reduced when using usual-intake models in comparison with the results obtained in the observed individual mean models, even if in terms of risk assessment the impact of using usual-intake models was limited. From the results it appears that the key aspects to consider when using usual-intake models are: (1) the normality of the log-transformed intake distribution, (2) the contribution per single food group to the total exposure, and (3) the independency of food consumption data on multiple days. In conclusion, usual-intake models may have an impact on exposure estimates although, referring to the results, it did not bring any changes in terms of risk assessment, but further investigations are needed.     

Sulfite content in some Brazilian wines: analytical determination and estimate of dietary exposure

Brazilian wines of different regions and that commercially available in the city of Campinas, SP, were analysed for their contents of sulfites. Dietary exposure to sulfites from Brazilian wines was also assessed by combining sulfite levels determined analytically with three hypothetical scenarios of daily wine consumption: 150, 300, and 450 mL. In all samples, the concentration of sulfites was below the maximum permitted level (MPL) of 350 mg L⁻¹ set in the Brazilian legislation with most samples (88%) containing residual sulfite below 150 mg L⁻¹. The dietary exposure to sulfites from regular consumption of 150 mL of national white wines containing sulfites at the mean level of 122.0 mg L⁻¹ covered 44% of the Acceptable Daily Intake (ADI) established by JECFA for these preservatives (0.7 mg kg⁻¹ bw). For high regular consumption (450 mL per day) of white wines, the dietary exposure could reach 131% of the ADI. In the case of national red wines (SO₂ mean level of 71.3 mg L⁻¹) the dietary exposure was lower, ranging from 26 to 76% of the ADI for 150 and 450 mL of daily consumption, respectively. The present study indicates that although sulfite levels in national wines is usually below the MPL (mean of 98.5 mg L⁻¹) a regular moderate consumption of 150 mL per day could lead to a dietary exposure of 15 mg of sulfites (0.25 mg kg⁻¹ bw in a 60-kg adult), covering one-third of the ADI. A regular heavy consumption (450 mL per day) would cover the full ADI.     

Long-term dietary exposure to lead in young European children: comparing a pan-European approach with a national exposure assessment

Long-term dietary exposures to lead in young children were calculated by combining food consumption data of 11 European countries categorised using harmonised broad food categories with occurrence data on lead from different Member States (pan-European approach). The results of the assessment in children living in the Netherlands were compared with a long-term lead intake assessment in the same group using Dutch lead concentration data and linking the consumption and concentration data at the highest possible level of detail. Exposures obtained with the pan-European approach were higher than the national exposure calculations. For both assessments cereals contributed most to the exposure. The lower dietary exposure in the national study was due to the use of lower lead concentrations and a more optimal linkage of food consumption and concentration data. When a pan-European approach, using a harmonised food categorisation system and “European” concentration data, results in a possible health risk related to the intake of an environmental chemical for a certain country, it is advisable to refine this assessment, as part of a tiered approach, using national occurrence data, including an optimised linkage between foods analysed and consumed for that country. In the case of lack of occurrence data, these data can be supplemented with data from the “European” concentration database or by generating additional concentration data at country level.     

Estimation of exposure to food packaging materials. 3: Development of consumption factors and food-type distribution factors from data collected on Irish children

There are many initiatives in Europe trying to refine the exposure assessment for food packaging migrants. In the USA, the US Food and Drug Administration (US FDA) uses food consumption and food-type distribution factors to aid the exposure assessment process and generate more realistic estimates of exposure. The present study developed food-consumption factors and food-type distribution factors for Irish children aged 5-12 years from data collected as part of a National Children's Food Survey (NCFS) completed in Ireland in 2003-04, combined with data from the 2003-05 Irish Food Packaging Database and from literature data on surface area-to-weight ratios for food packaging. Consumption factors are defined as the fraction of a person's diet likely to contact a specific food-contact material, while food-type distribution factors reflect the fraction of all food contacting each material that is aqueous, acidic, alcoholic or fatty. In this study, it was found that 'total plastics' had the highest consumption factor of 0.83, while 'total paper and board' had a factor of 0.13 and 'total metal and alloys' had a factor of 0.06. Although it is tentative to compare the US FDA factors with the factors derived in the current study, as the US FDA data are for the total US population, the consumption factor for 'total plastics' in the present study (0.83) was similar to that used by the US FDA (0.79). However, a large difference existed for the consumption factor for 'total metal and alloys' in the Irish data (0.06) and the US FDA data (0.2). In terms of the type of materials used for foods, glass was used mainly for acidic foods (0.67), while plastic was uniformly used for all food types. The food-contact area for plastic packaging for all foods consumed by children was 10.67 dm²/child day^-1, which is slightly lower than the proposed value for the average European consumer of 12.4 dm²/person day^-1. However, this should be expected, as children do not consume as much food as adults. When scenario exposure estimates were made, it was found that when using European Union assumptions, estimates were much larger than when using consumption factors and food-type distribution factors in the exposure assessment, even when conservative assumptions were employed for the consumption factor. This study highlights the potential use of consumption factors and food-type distribution factors in the refinement of the exposure assessment process and how these factors can be calculated using data collected as part of a national food survey.     

Evaluating daily exposure to polychlorinated biphenyls and polybrominated diphenyl ethers in fish oil supplements

Fish oil supplements have become a popular means of increasing one's dietary intake of essential polyunsaturated fatty acids. However, there is growing concern that the levels and potential health effects of lipophilic organic contaminants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) may diminish some of the health benefits associated with the daily consumption of fish oil supplements. In this study, ten over-the-counter fish oil supplements available in the United States were analysed for PCBs and PBDEs and daily exposures calculated. Based on manufacturers’ recommended dosages, daily intakes of PCBs and PBDEs ranged from 5 to 686 ng day^?1 and from 1 to 13 ng day^?1, respectively. Daily consumption of fish oil supplements expose consumers to PCBs and PBDEs. However, in comparison with fish ingestion, fish supplements may decrease daily PCB exposure and provide a safer pathway for individuals seeking to maintain daily recommended levels of polyunsaturated fatty acids.     

Assessment of seasonality in exposure to dioxins,furans and dioxin-like PCBs by using long-term food-consumption data

According to the European Food Safety Authority (EFSA) guidance related to uncertainties in dietary exposure assessment, exposure assessment based on short-term food-consumption surveys, such as 24-h recalls or 2-day records, tend to overestimate long-term exposure because of the assumption that the dietary pattern will be similar day after day over a lifetime. The aim of this study was to make an assessment of dietary exposure to polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), also called ‘dioxins’ and ‘dioxin-like PCBs’, using long-term household purchase and consumption survey data collected by TNS-Secodip. Weekly purchases of the major dioxins and dl-PCB vector products of these contaminants were collected for 328 single-person households, who participated at TNS-Secodip consumption surveys from 2003 to 2005 and who were single-person households in order to estimate better their consumption. These data were combined with average contamination levels of food products. Weekly gross average exposure was estimated at 10.2?pg toxic equivalent (WHO TEQ) kg^?1?bw?week^?1 (95% confidence interval [9.6, 10.9]). According to the typical shape of the distribution of individual weekly exposures, it is sensible to fit an exponential law to these data. The mean was therefore 12.1?pg WHO TEQ?kg^?1?bw?week^?1. This value is higher than the arithmetic mean because it better takes into account inter-individual variability. It was estimated that about 20% of persons in this sample were exceeding the current health-based guidance value mainly due to high consumption of seafood and/or dairy products. Thanks to long survey duration (3 years) and the weekly recording of food consumption, it was possible to demonstrate the actual seasonality of dietary exposure to dioxins and dl-PCBs with a maximum between March and September; similar seasonality is observable for fish consumption. Autoregressive integrated moving average (ARIMA) models were adjusted to the time series and it was demonstrated that the number of times the upper limit of confidence intervals exceeds the provisional tolerable weekly intake (PTWI) is about 15 weeks per year on average. Finally, compared with the results obtained from data collected in the short-term surveys (1 week), this study does not suggest that short-term consumption surveys tend to overestimate the long-term exposure.     

Migration of styrene monomer, dimers and trimers from polystyrene to food simulants

Migration experiments with polystyrene were performed in two-sided contact with n-heptane and distilled water as the food simulants at temperatures of 10, 24 and 40, and 40, 60 and 90°C, respectively. The surface/volume ratios in the migration cell were set at 8.04 and 10.05 dm² l^-1 for n-heptane and distilled water, respectively. Styrene monomer, styrene dimers and styrene trimers migrating to the food simulants were determined by GC-FID analysis. Heptane fully extracted the styrene monomer and the oligomers from the polystyrene sheet, whereas in the distilled water only the migrated styrene trimers could be detected. To determine the apparent diffusion coefficient, the migration process was analysed based on Fick's law. The higher the molecular weight of the oligomers, the more significant the reduction in the diffusion coefficient. Higher molecular weight oligomers also had lower activation energy of diffusion when the temperature dependence of diffusivity was analysed by the Arrhenius equation. The diffusion coefficient of the trimers was much higher for heptane contact than for water. The activation energy of the diffusion of trimers for water contact was higher than that for heptane.     

Application of triacylglycerol and fatty acid analyses to discriminate blended sesame oil with soybean oil

Triacylglycerols (TAGs) and fatty acids in the mixture of sesame oil (SO) with soybean oil were analysed using high performance liquid chromatography (HPLC)–an evaporative light scattering detector (ELSD) and gas chromatography (GC)–a flame ionisation detector (FID). Relative percentage of linolenic acid increased rapidly compared to those of oleic and linoleic acids as the ratio of soybean oil increased in the blended SO. Peak responses of trilinolein (LLL) and trilinolenin (LnLnLn) by HPLC–ELSD was higher than those by GC–FID from the same concentration of TAGs. The presence of LLLn peak, the contents of linolenic acid, and the relative ratio of L/S, O/Ln, and L/Ln from fatty acids or LLL/OOO from TAGs could be useful indicators to detect the blended SO with soybean oil. TAG analysis by HPLC–ELSD coupled with fatty acids by GC–FID can be useful methods to discriminate blended SO with soybean oil.     

Assessment of uncertainty in a probabilistic model of consumer exposure to pesticide residues in food

The assessment of consumer exposure to pesticides is an important part of pesticide regulation. Probabilistic modelling allows analysis of uncertainty and variability in risk assessments. The output of any assessment will be influenced by the characteristics and uncertainty of the inputs, model structure and assumptions. While the use of probabilistic models is well established in the United States, in Europe problems of low acceptance, sparse data and lack of guidelines are slowing the development. The analyses in the current paper focused on the dietary pathway and the exposure of UK toddlers. Three single food, single pesticide case studies were used to parameterize a simple probabilistic model built in Crystal Ball™. Data on dietary consumption patterns were extracted from National Diet and Nutrition Surveys, and levels of pesticide active ingredients in foods were collected from Pesticide Residues Committee monitoring. The effect of uncertainty on the exposure estimate was analysed using scenarios, reflecting different assumptions related to sources of uncertainty. The most influential uncertainty issue was the distribution type used to represent input variables. Other sources that most affected model output were non-detects, unit-to-unit variability and processing. Specifying correlation between variables was found to have little effect on exposure estimates. The findings have important implications for how probabilistic modelling should be conducted, communicated and used by policy and decision makers as part of consumer risk assessment of pesticides.     

Use of personal-indoor-outdoor sulfur concentrations to estimate the infiltration factor and outdoor exposure factor for individual homes and persons

A study of personal, indoor, and outdoor exposure to PM2.5 and associated elements has been carried out for 37 residents of the Research Triangle Park area in North Carolina. Participants were selected from persons expected to be at elevated risk from exposure to particles, and included 29 persons with hypertension and 8 cardiac patients with implanted defibrillators. Participants were monitored for 7 consecutive days in each of four seasons. One goal of the study was to estimate the contribution of outdoor PM2.5 to indoor concentrations. This depends on the infiltration factor Finf, the fraction of outdoor PM2.5 remaining airborne after penetrating indoors. After confirming with our measurements the findings of previous studies that sulfur has few indoor sources, we estimated an average Finf for each house based on indoor/outdoor sulfur ratios. These estimates ranged from 0.26 to 0.87, with a median value of 0.55. Since these estimates apply only to particles of size similar to that of sulfur particles (0.06-0.5 microm diameter), and since larger particles (0.5-2.5 microm) have lower penetration rates and higher deposition rates, these estimates are likely to be higher than the true infiltration factors for PM2.5 as a whole. In summer when air conditioners were in use, the sulfur-based infiltration factor was at its lowest (averaging 0.50) for most homes, whereas the average Finf for the other three seasons was 0.62-0.63. Using the daily estimated infiltration factor for each house, we calculated the contribution of outdoor PM2.5 to indoor air concentrations. The indoor-generated contributions to indoor PM2.5 had a wider range (0-33 microg/m3) than the outdoor contributions (5-22 microg/m3). However, outdoor contributions exceeded the indoor-generated contributions in 27 of 36 homes. A second goal of the study was to determine the contribution of outdoor particles to personal exposure. This is determined by the "outdoor exposure factor" Fpex, the fraction of outdoor PM2.5 contributing to personal exposure. As with Finf, we estimated Fpex by the personal/outdoor sulfur ratios. The estimates ranged from 0.33 to 0.77 with a median value of 0.53. Outdoor air particles were less important for personal exposures than for indoor concentrations, with the median outdoor contribution to personal exposure just 49%. We regressed the outdoor contributions to personal exposures on measured outdoor PM2.5 at the central site. The regressions had R2 values ranging from 0.19 to 0.88 (median = 0.73). These values provide an indication of the extent of misclassification error in epidemiological estimates of the effect of outdoor particles on health.     

Pesticide residue assessment in different types of olive oil and preliminary exposure assessment of Greek consumers to the pesticide residues detected

In this study the occurrence and levels of multi-class pesticides in different types of virgin olive oil quality and origination were determined and the contribution of olive oil in the chronic risk of pesticide residues consumption in the Mediterranean diet was estimated. For this purpose, a multiresidue method for the determination of 35 pesticides in olive oil was evaluated and applied to a total number of 100 olive oil samples. Ten percent of the samples produced from fruits of conventional cultivations contained no detectable residues whereas in the rest samples were detected residues of 20 insecticides. The highest detection rates were observed for the residues of fenthion, dimethoate and endosulfan. The highest occurrence and levels of pesticides were observed in extra virgin olive oil whereas results pointed that residues in olive oil from variety of olives with high oil yield may be higher. Furthermore, olive oil from organic cultivations could be contaminated with pesticide residues and/or contain low levels of pesticide residues that are not registered for use in olive cultivations. For there were multiresidues of pesticides present in olive oil, there is no zero risk in consumption of olive oil. However, the exposure of olive oil consumers to each detected residue is far below the acceptable daily intake (ADI).     

Dietary exposure and risk assessment to lead of the population of Jiangsu province,China

The paper’s main purpose is to estimate the dietary exposure to lead for the inhabitants of Jiangsu province, China. Lead concentration data were obtained from the national food contamination monitoring programme during 2007–10. Food samples (n = 2077) were collected from 23 food categories in Jiangsu province. Consumption data were derived from Chinese national nutrition and health survey in 2002, which included 3938 inhabitants from 1451 households in Jiangsu province. Concentration data were combined with consumption data to estimate the dietary intake for the inhabitants of 2–6, 7–17 and 18–80 years, respectively. The β-binomial–normal (BBN) model was used to estimate the long-term intake for the population in Jiangsu province. The distribution of individual margin of exposure (IMoE) was introduced to assess the health effect. Uncertainty of IMoE was quantified by Monte Carlo and bootstrap methods. The mean levels of dietary exposure to lead were estimated at 3.019 µg kg^?1 bw day^?1 for children aged 2–6 years, 2.104 µg kg^?1 bw day^?1 for teenagers aged 7–17 years, and 1.601 µg kg^?1 bw day^?1 for adults aged 18–80 years. The mean intakes for the urban and rural populations were 1.494 and 1.822 µg kg^?1 bw day^?1, respectively. From the 25th to 99.9th percentiles, IMoE was 0.125–2.057 for 2–6 years and 0.473–7.998 for 18–80 years, respectively. The distribution of IMoE could indicate a public health concern on lead for the Chinese population in Jiangsu. Control measures should be taken to reduce lead exposure in Jiangsu province.     

Residual susceptibility of Plodia interpunctella to deltamethrin dust: Effects of concentration and time of exposure

Wandering phase fifth instarPlodia interpunctella (Hübner) were exposed at ten weekly intervals for 6, 12 and 24 h or 1 week to 0.05% deltamethrin dust at application rates of 38, 47 and 56 mg per 0.016 m². The percentages of pupating larvae and adult emergence at all three rates were greatest at the 6-h exposure and least at the 1-week exposure, but there was no consistent decrease in pupation or emergence as the exposure was increased from 6 to 24 h. Pupation and emergence decreased with increasing application rate of deltamethrin dust at each weekly bioassay, and the percentage of emerged adults was usually less than the percentage of larvae that pupated. At the conclusion of the test (9 weeks), curve-fit adult emergence data for larvae exposed for 1 week to deltamethrin dust at application rates of 38, 47 and 56 mg per 0.016 m² were calculated by linear regression to be 26.6%, 20.5% and 17.3% respectively. For all other exposure times at each rate, adult emergence usually exceeded 20% after 2–4 weeks.