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PubMed2001

The effect of system design on bacterial contamination of enteral tube feeds.

The effect of recent changes in system design on the levels and incidence of bacterial contamination in enteral tube feeds was examined by comparing two different systems. Adult patients who had been identified as requiring enteral tube feeding were allocated to receive sterile, whole protein enteral feed from either 2 x 1000 mL triple foil laminated pouches (Nutrison Standard, Nutrison Pack, Nutricia Ltd, UK) attached to a Flocare 800 pack giving set or from 2 x 1000 mL rigid plastic bottles (Osmolite, Ross Ready-to-Hang, Abbott Laboratories, UK) connected to a Patrol Pump set. Samples of feed from the nutrient containers were sent for microbiological analysis each time the container was changed (12 and 24 h) and samples from the distal ends of giving sets after 24 h.Bacterial contamination was found in a significantly lower number of Nutrison Packs (14/120; 12%) as compared with Ross Ready-to-Hang containers (25/120; 21%) (Fisher's exact test, 1 tailed test, P > or = 0.05). However, both the level and frequency of contamination of the feed samples collected from the distal ends of the giving sets of both types of system were similar to each other but higher than those from the nutrient containers (57/120 contaminated giving sets as compared with 39/240 nutrient containers; P > or = 0.00001). On 32/120 patient days only the giving set samples were contaminated. The results highlight the important role that improvements in system design, such as the use of recessed spikes on giving sets have in reducing the risk of bacterial contamination of enteral tube feeds introduced due to faulty handling procedures, and further implicate retrograde spread of the patients' own flora as a source of contamination in the giving set.

Adult↗

PubMed2002

Contaminated operating room boots: the potential for infection.

BACKGROUND: Dirty operating room boots, often contaminated with blood and other infected material, are not only a source of discontent among surgeons and other surgical personnel, but they also pose a potential risk of transmission of viral or bacterial diseases to the wearer and cleaner of the boots. METHOD: Operating room boots were examined for the presence of blood by visual inspection; the presence or absence of blood was confirmed by a specific biochemical test. Bacterial isolation and quantification from boots were performed with conventional methodology. RESULTS: In this study, a spot check revealed that 44% of all operating room boots tested were contaminated with blood and that the majority were contaminated with bacteria. Sixty-three percent of surgeons using the facility had blood-contaminated boots, and a significant number of boots belonging to other surgical personnel were also contaminated with blood and bacteria normally associated with skin microbiota or the environment. Comfort shoes with perforations on their upper surface and plastic boots commonly found in operating rooms were most heavily contaminated, whereas Wellington boots and clogs had less contamination. CONCLUSION: The present practice of manual cleaning of boots is unsatisfactory, and it is recommended that boots be washed in automatic washing machines.

Blood↗

PubMed2002

Effects of Fusarium toxin contaminated wheat and of a detoxifying agent on performance of growing bulls, on nutrient digestibility in wethers and on the carry over of zearalenone.

Experiments were carried out to examine the effects of a Fusarium contaminated wheat (10 mg deoxynivalenol and 0.76 mg zearalenone, ZON, per kg dry matter) and of a detoxifying agent (Mycofix Plus, Biomin GmbH, Herzogenburg, Austria) on the growing performance of bulls, carry-over of ZON and its metabolites into body fluids and tissues, and on nutrient digestibility in wethers. The experiments were designed according to a complete two by two factorial approach which meant that both the uncontaminated control wheat and the Fusarium toxin contaminated wheat were tested both in the absence and presence of Mycofix Plus. The growing experiment with bulls (n = 14 per treatment) covered the live weight range between 244 kg and 460 kg. The respective wheat batches were included in the concentrate portion at 65%. Concentrates were fed according to plan whereas maize silage was offered for ad libitum consumption. Daily dry matter intake and live weight gain [kg per animal and day] were 7.40, 7.52, 7.51 and 7.49 and 1.367, 1.296, 1.380 and 1.307 for bulls fed the unsupplemented control wheat, the supplemented control wheat, the unsupplemented and Fusarium toxin contaminated wheat and the supplemented Fusarium toxin contaminated wheat, respectively. ZON and its metabolites were not detected in edible tissues. The most striking effects of feeding the Fusarium toxin contaminated wheat on carcass characteristics were a reduced dressing percentage, an increased weight of the emptied gastro-intestinal tract and a reduced weight of the testicles. No effect of the detoxifying agent was seen for these parameters whereas heart weight increased independently of Fusarium toxin contamination of the concentrates. Nutrient digestibility of the two wheat batches, unsupplemented or supplemented with Mycofix Plus was evaluated according to the difference method using wethers. Presence of Fusarium toxins in wheat did not influence its feeding value. The effects of the addition of the detoxifying agent were mycotoxin unspecific and resulted in an increase in apparent digestibility of crude protein and a decrease in crude fiber digestibility. It is concluded that feeding of Fusarium toxin contaminated wheat did not adversely affect performance of growing bulls (approximately 2.2 mg DON and 0.1 mg ZON per kg complete ration at a reference dry matter content of 88%) or nutrient digestibility in wethers. The effects of the detoxifying agent Mycofix Plus on growing performance and on nutrient digestibility were rather Fusarium toxin unspecific. The slightly negative effects on growing performance needs to be examined further.

Animal Feed↗

PubMed1998

Mycoplasma contamination of Chlamydia pneumoniae isolates.

We examined 6 C. pneumonia isolates from The American Type Culture Collection (ATCC) and 2 Finnish isolates for Mycoplasma contamination. Three of the ATCC isolates and both of the Finnish isolates were Mycoplasma-contaminated. The contaminants were characterized by means of growth in BEa and BEg media, immunoblotting, polymerase chain reaction and pulsed field gel electrophoresis. Two of the 6 ATCC isolates [ATCC VR1355 (TWAR strain 2043) and ATCC VR1356 (TWAR strain 2023)] were infected with Mycoplasma hominis and 1 isolate [ATCC VR2282 (TWAR strain TW183)] was contaminated with both Mycoplasma hominis and Mycoplasma orale, whereas 3 of the ATCC isolates [ATCC VR1310, ATCC VR1360 (TWAR strain CM-1) and ATCC 53592 (TWAR strain AR39)] were not contaminated. The Finnish C. pneumoniae isolates Kajaani 6 and Parola were found to be contaminated with M. hominis and M. orale, respectively. The contamination of C. pneumoniae stock cultures, frequently used in the microimmunofluorescence test, with human pathogens, could pose a serious problem in C. pneumoniae serology.

Bacteriological Techniques↗

PubMed2002

International legislation on trace elements as contaminants in food: a review.

Environmental contaminants such as trace elements may be present in all foods. Foods, raw materials and ingredients for food production are to an increasing extent traded across borders. Hence, there is a need for international legislation on trace elements as contaminants in food. In 1961, the FAO and WHO established the Codex Alimentarius to elaborate international food legislation. Contaminants in food are handled by the Codex Committee for Food Additives and Contaminants (CCFAC). The Codex Alimentarius system for developing legislation concerning trace elements as contaminants in food is based upon the Codex General Standard for Contaminants and Toxins in Food (GSCTF). By October 2001, the principles for setting maximum limits (MLs) for contaminants in food are agreed, and work is in progress on MLs for trace elements such as lead and cadmium in the various food categories. The status for the proposals is presented and discussed. The EU Regulation 466/2001 of 8 March 2001 sets MLs for lead and cadmium in various foods. This regulation will apply from 5 April 2002. The EU regulation is more detailed but similar to the Codex draft standards for lead and cadmium in food. In future, legislators and administrators in the Codex and EU and analytical chemists will discuss how to use more and better analytical data as risk-management tools to protect public health. Trace elements' speciation is an important aspect of this discussion.

European Union↗

PubMed2003

Effects of contaminants on bait acceptance by Solenopsis invicta (Hymenoptera: Formicidae).

Three commonly used fire ant baits, Amdro (0.73% hydramethylnon [AI]), Ascend (0.011% abamectins [AI]), and Maxforce (1.0% hydramethylnon [AI]), were exposed to potential, volatile contaminants. The contaminants included the insecticides Orthene Fire Ant Killer (75.0% acephate [AI] ), Cyren (44.6% chlorpyrifos [AI]), and Tempo 2 (24.3% cyfluthrin [AI]); cigarette smoke; gasoline (unleaded, 89 octane); and fertilizer (10-10-10). Fire ant baits previously exposed for 48 h to these contaminants were analyzed using gas chromatography analysis. Orthene Fire Ant Killer, Cyren, Tempo 2, cigarette smoke, and gasoline had volatile components transferred to the baits. Baits exposed to these products were used in a field evaluation of bait acceptance by Solenopisis invicta Buren, the red imported fire ant. Uncontaminated Amdro was significantly preferred by S. invicta over Amdro contaminated by smoke, Cyren, Tempo 2, and gasoline. Uncontaminated Maxforce was significantly preferred over Maxforce contaminated by Tempo 2, Cyren, and gasoline, and uncontaminated Ascend was preferred over Tempo 2- and Cyren-contaminated Ascend. Orthene-exposed Amdro, Maxforce, and Ascend baits, and smoke-exposed Maxforce and Ascend baits were not significantly different from the control. These results indicate that volatile insecticides and products can contaminate fire ant baits. Some insecticides and products, such as gasoline, can significantly affect bait palatability and may adversely impact control.

Animals↗

PubMed2004

Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on performance and metabolism of laying hens.

An experiment was conducted to evaluate the effects of feeding laying hens grains naturally contaminated with a combination of Fusarium mycotoxins. Parameters measured included performance, organ weights, and plasma chemistry. One hundred and forty-four, 45-wk-old laying hens were fed diets including: (1) control, (2) contaminated grains, and (3) contaminated grains + 0.2% polymeric glucomannan mycotoxin adsorbent (GMA) for a 12-wk period. The feeding of contaminated grains decreased feed consumption compared with controls in the first 4 wk. Feed consumption increased, however, from 4 to 8 wk and from 8 to 12 wk. The efficiency of feed utilization (feed consumption/egg mass) decreased compared with controls in the periods from 4 to 8 and from 8 to 12 wk when birds were fed contaminated grains. Supplementation with GMA decreased feed consumption and increased the efficiency of feed utilization in the period from 8 to 12 wk. Egg production and egg mass decreased in wk 4 and 8 compared with controls when contaminated grains were fed, whereas egg and eggshell weights decreased in the fourth wk. Plasma uric acid concentrations increased throughout the experiment and relative kidney weights increased at the end of the experiment compared with controls when birds were fed contaminated grains. The feeding of GMA prevented the elevation in uric acid concentrations and relative kidney weights. It was concluded that layer performance and metabolism were adversely affected by chronic feeding of a combination of Fusarium mycotoxins, and that GMA prevented many of these effects.

Adsorption↗

PubMed2000

Bacterial contamination of ready-to-use 1-L feeding bottles and administration sets in severely compromised intensive care patients.

OBJECTIVE: In intensive care patients, enteral feeding requires sterile feedings because of infectious complications and adequate supplements to meet nutritional needs. Heretofore, prepacked, large-volume formula containers were developed, but bacterial contamination occurred in 4% to 15%. Our objective was to investigate the microbial contamination rate of 1-L feeding bottles and newly designed administration sets over hanging times of 24 hrs in the intensive care unit (ICU). DESIGN AND SETTING: A prospective observational cohort study of patients admitted to the ICU of a university hospital. PATIENTS: All consecutive patients fed via a nasojejunal tube for at least 4 days. MEASUREMENTS: Cultures of feeding bottles, administration sets, and gastric and tracheobronchial aspirates at day 0, 1, 2, 4, and 7. RESULTS: A total of 4% of feeding bottles and 74% of infusion sets contained >10(2) colony forming units (CFU)/mL. Gastric and bronchial aspirates were positive in 90% and 92%, respectively. Bacterial counts of feeding bottles were 10(2)-10(5) CFU/mL, and the main bacteria isolated included Enterobacter cloacae, Klebsiella oxytoca, and enterococci. One third of all cultured bacteria in feeding bottles, administration sets, stomach, and lungs belonged to the Enterobacteriaceae family, which was held responsible for the nosocomial infections in the ICU. None of the 1-L feeding bottles with a hanging time of 19-24 hrs was contaminated. Only bottles that had to be exchanged because of need for a faster rate of infusion proved to be contaminated, apparently without clinical consequences. With time and the increasing severity of disease, the administration sets became contaminated at an increasingly faster rate and with higher bacterial counts mainly through retrograde growth of endogenous bacteria. The final step of bottle contamination might have been the bacterial transfer by nurses' hands. CONCLUSION: Despite an almost ideal design of the enteral nutrition delivery system, a 4% contamination rate of initially sterile feedings with clinically relevant bacteria and the fact that only manipulated systems showed bacterial growth are of concern.

APACHE↗

PubMed2002

Unexpected high risk of contamination with staphylococci species attributable to standard preparation of syringes for continuous intravenous drug administration in a simulation model in intensive care units.

OBJECTIVE: To determine the risk of bacterial contamination of the infusate in a simulation model of syringes prepared for continuous intravenous drug administration by intensive care unit nurses. Widely accepted standard procedures in the intensive care unit were compared with syringes prepared by pharmaceutical technicians working under standard aseptic conditions according to national guidelines. DESIGN: Prospective study. SETTING: Intensive care units of four general teaching hospitals and two university hospitals. SUBJECTS: We examined 650 syringes prepared from 10-mL ampules and 100 syringes prepared from rubber-compound-capped 50-mL vials by intensive care unit nurses of six hospitals. Also, 100 syringes from 10-mL ampules and 100 syringes from rubber-compound-capped 50-mL vials were prepared by pharmaceutical technicians. INTERVENTIONS: Turbidity of syringes after culturing for 7 days at 37 degrees C was used as the criterion for possible bacterial contamination, which was proved with subsequent Gram staining. MEASUREMENTS AND MAIN RESULTS: A median contamination rate of 22% (range, 7% to 44%) was observed for the syringes prepared from 10-mL ampules by intensive care unit nurses, compared with only 1% for the syringes prepared from ampules by technicians (p <.001). In >75% of all contaminated syringes, Gram-positive cocci were identified. At least 12% of all prepared syringes proved to be contaminated with staphylococci species. The contamination rate of syringes prepared from vials was much lower: 2% in the intensive care unit and 0% at the department of clinical pharmacy. CONCLUSIONS: In the intensive care unit, standard procedures for preparing syringes for intravenous administration of drugs lack vigorous aseptic precautions, leading to a high contamination rate of the infusate. This risk is increased when ampules instead of 50 mL-vials are used to prepare the syringes.

Equipment Contamination↗

PubMed1997

Removable surface contamination at a biomedical research institution.

A rigorous, unannounced, campus-wide survey for removable surface contamination was performed at our institution. Wipe samples (n = 1,090) were collected from a variety of standardized locations in 45 large biomedical research laboratories that routinely use kBq-MBq (microCi-mCi) amounts of 3H, 14C, 32P, 35S, 51Cr, and 125I. The results showed a log-normal distribution for contamination, with about 90% of all samples below ten times background. Although working surfaces and equipment used in these laboratories can become contaminated with radioactive materials, especially by transfer from soiled gloves, the magnitude of the contamination is very small and typically restricted to surfaces, instruments, and equipment that are directly handled in the course of experimental work and which can be reasonably anticipated to be contaminated. These data suggest that contamination is not a significant problem in biomedical research laboratories at this institution and that the best protection from workplace contamination appears to continue to be the use of well-reviewed standard operating procedures and good work practices.

Carbon Radioisotopes↗

PubMed2006

Reducing contamination when removing and storing corneas: a multidisciplinary, transversal, and environmental approach.

PURPOSE: The combination of a shortage of cornea grafts in France and a national average contamination rate of 9% to 10%, has led us to search for the origins of this contamination. The objective of our study was to reduce the number of unusable grafts resulting from contamination of corneas in organ culture. METHODS: An external audit was carried out by an independent pharmacist on the removal conditions and treatment procedures for corneas. An environmental study was carried out, consisting of microbiological sampling of the corneas of donors who just died (<24 hours) as well as water and air samples in the premises used for removal. The Cornea Bank's procedures were submitted to a microbiological risk analysis using the "failure mode effects and criticity analysis" (FMECA) method. RESULTS: The critical contamination periods were found to be before removal, during mortuary washing and during decontamination of the conjunctival cul-de-sac at the removal stage. The corrective measures taken have reduced contamination rates by half in 1 year. CONCLUSION: Highlighting the sources of contamination has led to the implementation of effective targeted and low-cost measures that have allowed us to reduce significantly the number of cornea graft losses as a result of bacterial and fungal contamination.

Cornea↗

PubMed2003

Use of incubation time to detection in BACTEC 9240 to distinguish coagulase-negative staphylococcal contamination from infection in pediatric blood cultures.

BACKGROUND: Growth of coagulase-negative staphylococci (CoNS) in a blood culture indicates infection or contamination. Differentiation may be difficult in pediatric patients from whom only a single blood culture is commonly obtained. METHODS: We evaluated the use of the incubation time to detection of growth [time to positive (TTP)] of CoNS in a continuously monitored blood culture system (BACTEC Peds/F bottles in BACTEC 9240) to differentiate infection from contamination. Three groups of febrile pediatric patients with blood cultures growing CoNS were identified: Group 1, children with vascular catheter-associated bloodstream infection; Group 2, previously healthy children with a contaminant; Group 3, chronically ill children with a contaminant. RESULTS: The median TTP for blood cultures from the 17 infection episodes, 11 h [mean, 13.2 h; 95% confidence interval (CI), 11.4 to 17.7], was significantly shorter than either the 30 episodes in the previously healthy group with contaminant, median 19 h (mean, 22.7 h; 95% CI 19.5 to 26.2; P < 0.0001) or the 12 episodes in the chronically ill group with contaminant, median 24 h (mean, 35.2 h; 95% CI 17.2 to 53.1; P < 0.0001). A TTP of < or =15 h had a positive predictive value of 84% for diagnosis of infection. A TTP of > or =22 h had a positive predictive value of 87% for diagnosis of contaminant. CONCLUSION: In our experience the TTP was a useful adjunctive test to determine the clinical significance of isolation of CoNS from a blood culture from a pediatric patient.

Bacteremia↗

PubMed2006

Estimation of microbial contamination of food from prevalence and concentration data: application to Listeria monocytogenes in fresh vegetables.

A normal distribution and a mixture model of two normal distributions in a Bayesian approach using prevalence and concentration data were used to establish the distribution of contamination of the food-borne pathogenic bacteria Listeria monocytogenes in unprocessed and minimally processed fresh vegetables. A total of 165 prevalence studies, including 15 studies with concentration data, were taken from the scientific literature and from technical reports and used for statistical analysis. The predicted mean of the normal distribution of the logarithms of viable L. monocytogenes per gram of fresh vegetables was -2.63 log viable L. monocytogenes organisms/g, and its standard deviation was 1.48 log viable L. monocytogenes organisms/g. These values were determined by considering one contaminated sample in prevalence studies in which samples are in fact negative. This deliberate overestimation is necessary to complete calculations. With the mixture model, the predicted mean of the distribution of the logarithm of viable L. monocytogenes per gram of fresh vegetables was -3.38 log viable L. monocytogenes organisms/g and its standard deviation was 1.46 log viable L. monocytogenes organisms/g. The probabilities of fresh unprocessed and minimally processed vegetables being contaminated with concentrations higher than 1, 2, and 3 log viable L. monocytogenes organisms/g were 1.44, 0.63, and 0.17%, respectively. Introducing a sensitivity rate of 80 or 95% in the mixture model had a small effect on the estimation of the contamination. In contrast, introducing a low sensitivity rate (40%) resulted in marked differences, especially for high percentiles. There was a significantly lower estimation of contamination in the papers and reports of 2000 to 2005 than in those of 1988 to 1999 and a lower estimation of contamination of leafy salads than that of sprouts and other vegetables. The interest of the mixture model for the estimation of microbial contamination is discussed.

Bayes Theorem↗

PubMed1986

Comparison of the standard pour plate procedure and the ATP and Limulus amebocyte lysate procedures for the detection of microbial contamination in intravenous fluids.

The intrinsic and extrinsic microbial contamination of large-volume parenterals has been associated with bacteremias in hospitalized patients. When epidemiologic data suggest the association of contaminated intravenous (i.v.) fluids with disease, appropriate laboratory methods must be devised to analyze quickly the suspect fluid. A study was undertaken to compare three laboratory test methods (standard pour plate [SPP] technique, ATP procedure, and Limulus amebocyte lysate [LAL] assay) for detecting the presence of microorganisms in artificially contaminated i.v. fluid. SPP proved the most sensitive of the assay techniques used, but a 24-h period was required for microbial growth. The LAL assay appeared more sensitive in detecting i.v. contamination than the ATP method. These studies suggest that the LAL and ATP methods can be used for the rapid detection of microbial contamination in i.v. fluid. SPP and LAL procedures would have practical laboratory application when the contamination of i.v. fluids is suspected, and they are more sensitive in detecting microbial contamination in these solutions than the ATP method.

Adenosine Triphosphate↗

PubMed1999

Cross contamination of blood cultures associated with a multiple use venting device.

AIM: To investigate cross contamination of blood cultures associated with multiple use venting devices, which are widely used in clinical microbiology laboratories to reduce labour costs. METHODS: Systematic analysis of 13,880 blood culture results in a large teaching hospital where multiple use venting devices were employed. RESULTS: Nine series of potential cross contamination were identified in a 12 month period. Four series involved coagulase negative staphylococci and were unlikely to represent true cross contamination. Five series involved blood cultures which had significant bacterial growth at the time of venting. CONCLUSIONS: Multiple use venting devices can be associated with cross contamination of blood cultures. This may result from contamination of the internal lumen of the venting device which is not exposed to the biocide. Medical microbiologists should consider the possibility of cross contamination associated with venting procedures when interpreting blood culture results. Further development of multiple use venting devices is required to reduce the risk of cross contamination of cultures.

Equipment Contamination↗

PubMedDate not supplied

Microbial contamination of continuous drip feedings.

We evaluated the extent and effects of bacterial contamination of an open continuous enteral feeding system. Eighty-two quantitative enteral feeding cultures and clinical data were obtained during 8 days of observation on each of 33 patients. Cultures of appropriate sites were obtained on febrile patients and compared to the enteral feeding culture. Gram negative bacilli (GNB) in the enteral feeding correlated with abdominal distension in the patients (10 of 12 patients with GNB compared to 5 of 21 without GNB; p less than 0.01). Nine of the 10 patients with GNB and distension were receiving systemic antimicrobics to which the organism was resistant. Contamination of feeding with Serratia marcescens correlated with cultures for the same organism in patients' other body sites (p less than 0.01). The feeding contaminant may have been the source of sepsis in one patient who expired from septic shock. No relationship was demonstrated between contamination and liquid stools or fever. Undiluted, canned feedings were significantly less contaminated at 24 hr (15%) than those requiring mixing of powder (94%) (p less than 0.0001). The canned feedings grew primarily enteric organisms, whereas the powder feedings grew flora typically resident on the skin. Mixing or diluting feedings appears to represent an increased risk of contamination. Growth of GNB may produce adverse effects. Further investigation into methods to limit contamination and growth is warranted.

Adolescent↗

PubMed2005

Biologically active contaminants of intravenous saline in PVC packaging: Australasian, European, and North American samples.

We have previously found evidence of contaminants in 0.9% saline packaged in polyvinyl chloride (PVC) for clinical use. For this current study we asked two questions: (1) what are the organic chemical contaminants in solutions packaged in PVC? and (2) do the contaminants vary in bags manufactured in different countries? We studied samples of 0.9% saline packaged in PVC from Australasia, Europe, and North America. We analysed the saline solutions with high-resolution capillary gas chromatography - mass spectrometry. Components of the Australasian and European bags were also analysed using thermodesorption followed by gas chromatography and mass spectrometry. In three pairs of samples we found twenty-four different organic contaminants of the saline solutions. Diethylhexyl phthalate (DEHP) was found in all solutions; the concentrations were greater than 10 microg/l in the Australasian and European samples. All samples contained 2-ethyl hexanol (>50 microg/l), a DEHP breakdown product. The Australasian and North American samples contained cyclohexanone at concentrations of about 1000 microg/l. The cyclohexanone probably originated in joints at the bases of the bags. Both the Australasian and European bags contained t-butyl cyclohexanol (>500 microg/l) and t-butyl cyclohexanone (>50 microg/l). Printing ink on the outside of the bags was the most likely source for both of these contaminants. Several of the contaminants are toxic to animals. Little is known about the toxicity of combinations of contaminants.

Australia↗

PubMed2004

Proceedings of the workshop on food-consumption surveys in developing countries: general approaches to estimation of dietary exposure to contaminants.

The initial steps in estimating dietary exposure to contaminants include gathering the necessary expertise, clarifying the intent and purpose of the work, selecting a dietary exposure model, and gathering available pertinent information. Expertise is generally needed in chemistry, agriculture, toxicology, statistics, nutritional epidemiology, and computer software development. The goal might be to determine the average exposure of a population to contaminants, to identify demographic groups within a population that are especially vulnerable to a contaminant, to evaluate the regulation of agricultural and food-manufacturing practices, or to determine compliance with standards for local and/or imported foods. Examples of dietary exposure models include the core food model, directed core food model, large database model, raw agricultural commodity (RAC) model, regional diet model, duplicate diet model, and total diet composite model. Each model has advantages and disadvantages and different costs and resource requirements. Consideration of the sources and flow of selected contaminants though the food supply may help identify the best exposure model to use. Pertinent information that may already be available includes analytical data on contaminants in foods or commodities, government regulations pertaining to the levels of contaminants in foods, food-consumption data, data on the average body weights of age-gender groups (to express exposure on a body weight basis), and biochemical measures of contaminants or their residues/metabolites. Collecting available information helps to clearly define what critical information is missing so that the planned research can be most effective. Careful documentation of decisions and assumptions allows for recalculating exposure estimates with the same model using different decisions and assumptions; documentation also allows others to understand what was done and how to use the resulting intake estimates properly. Clearly identifying the limitations of the exposure model may provide justification for additional resources to further refine and improve the model.

Developing Countries↗