Education of staff in preschool aged classrooms in child care centers and child outcomes: A meta-analysis and systematic review

Staff education is considered key to quality of early childhood education and care (ECEC) programs. However, findings about associations between staff education and children's outcomes have been inconsistent. We conducted a systematic review and meta-analysis of associations between ECEC staff education and child outcomes. Searches of Medline, PsycINFO, and ERIC, websites of large datasets and reference sections of all retrieved articles were conducted. Eligible studies provided a statistical link between staff education and child outcomes for preschool-aged children in ECEC programs. Titles, abstracts and paper reviews as well as all data extraction were conducted by two independent raters. Of the 823 studies reviewed for eligibility, 39 met our inclusion criteria. Research in this area is observational in nature and subject to the inherent biases of that research design. Results from our systematic review were hampered by heterogeneity in how staff education was defined, variability in whose education was measured and the child outcomes that were assessed. However, overall the qualitative summary indicates that associations between staff education and childhood outcomes are non-existent to very borderline positive. In our meta-analysis of more homogeneous studies we identified certain positive, albeit very weak, associations between staff education and children's language outcomes (specifically, vocabulary and letter word identification) and no significant association with a mathematics outcome (WJ Applied Problems). Thus, our findings suggest that within the range of education levels found in the existing literature, education is not a key driver of child outcomes. However, since we only explored levels of education that were reported in the literature, our findings cannot be used to argue for lowering education standards in ECEC settings.

The relationship between the Early Childhood Environment Rating Scale and its revised form and child outcomes: A systematic review and meta-analysis

The Early Childhood Environment Rating Scale (ECERS) and its revised version (ECERS-R) were designed as global measures of quality that assess structural and process aspects of Early Childhood Education and Care (ECEC) programs. Despite frequent use of the ECERS/ECERS-R in research and applied settings, associations between it and child outcomes have not been systematically reviewed. The objective of this research was to evaluate the association between the ECERS/ECERS-R and children’s wellbeing. Searches of Medline, PsycINFO, ERIC, websites of large datasets and reference sections of all retrieved articles were completed up to July 3, 2015. Eligible studies provided a statistical link between the ECERS/ECERS-R and child outcomes for preschool-aged children in ECEC programs. Of the 823 studies selected for full review, 73 were included in the systematic review and 16 were meta-analyzed. The combined sample across all eligible studies consisted of 33, 318 preschool-aged children. Qualitative systematic review results revealed that ECERS/ECERS-R total scores were more generally associated with positive outcomes than subscales or factors. Seventeen separate meta-analyses were conducted to assess the strength of association between the ECERS/ECERS-R and measures that assessed children’s language, math and social-emotional outcomes. Meta-analyses revealed a small number of weak effects (in the expected direction) between the ECERS/ECERS-R total score and children’s language and positive behavior outcomes. The Language-Reasoning subscale was weakly related to a language outcome. The enormous heterogeneity in how studies operationalized the ECERS/ECERS-R, the outcomes measured and statistics reported limited our ability to meta-analyze many studies. Greater consistency in study methodology is needed in this area of research. Despite these methodological challenges, the ECERS/ECERS-R does appear to capture aspects of quality that are important for children’s wellbeing; however, the strength of association is weak.

Child-Staff Ratios in Early Childhood Education and Care Settings and Child Outcomes: A Systematic Review and Meta-Analysis

Child-staff ratios are a key quality indicator in early childhood education and care (ECEC) programs. Better ratios are believed to improve child outcomes by increasing opportunities for individual interactions and educational instruction from staff. The purpose of this systematic review, and where possible, meta-analysis, was to evaluate the association between child-staff ratios in preschool ECEC programs and children’s outcomes. Searches of Medline, PsycINFO, ERIC, websites of large datasets and reference sections of all retrieved articles were conducted up to July 3, 2015. Cross-sectional or longitudinal studies that evaluated the relationship between child-staff ratios in ECEC classrooms serving preschool aged children and child outcomes were independently identified by two reviewers. Data were independently extracted from included studies by two raters and differences between raters were resolved by consensus. Searches revealed 29 eligible studies (31 samples). Child-staff ratios ranged from 5 to 14.5 preschool-aged children per adult with a mean of 8.65. All 29 studies were included in the systematic review. However, the only meta-analysis that could be conducted was based on three studies that explored associations between ratios and children’s receptive language. Results of this meta-analysis were not significant. Results of the qualitative systematic review revealed few significant relationships between child-staff ratios and child outcomes construed broadly. Thus, the available literature reveal few, if any, relationships between child-staff ratios in preschool ECEC programs and children’s developmental outcomes. Substantial heterogeneity in the assessment of ratios, outcomes measured, and statistics used to capture associations limited quantitative synthesis. Other methodological limitations of the research integrated in this synthesis are discussed.

A Systematic Review and Meta-Analysis of a Measure of Staff/Child Interaction Quality (the Classroom Assessment Scoring System) in Early Childhood Education and Care Settings and Child Outcomes

The quality of staff/child interactions as measured by the Classroom Assessment Scoring System (CLASS) in Early Childhood Education and Care (ECEC) programs is thought to be important for children's outcomes. The CLASS is made of three domains that assess Emotional Support, Classroom Organization and Instructional Support. It is a relatively new measure that is being used increasingly for research, quality monitoring/accountability and other applied purposes. Our objective was to evaluate the association between the CLASS and child outcomes. Searches of Medline, PsycINFO, ERIC, websites of large datasets and reference sections of all retrieved articles were conducted up to July 3, 2015. Studies that measured association between the CLASS and child outcomes for preschool-aged children who attended ECEC programs were included after screening by two independent reviewers. Searches and data extraction were conducted by two independent reviewers. Thirty-five studies were systematically reviewed of which 19 provided data for meta-analyses. Most studies had moderate to high risk of bias. Of the 14 meta-analyses we conducted, associations between Classroom Organization and Pencil Tapping and between Instructional Support and SSRS Social Skills were significant with pooled correlations of .06 and .09 respectively. All associations were in the expected direction. In the systematic review, significant correlations were reported mainly from one large dataset. Substantial heterogeneity in use of the CLASS, its dimensions, child outcomes and statistical measures was identified. Greater consistency in study methodology is urgently needed. Given the multitude of factors that impact child development it is encouraging that our analyses revealed some, although small, associations between the CLASS and children's outcomes.

An examination of clients' in-session changes and their relationship to the working alliance and outcome

The objective of the current study was to investigate the psychometric properties of the Client Task Specific Change Measure-Revised (CTSC-R), a measure of clients' in-session changes, and to determine whether the CTSC-R predicted outcome over and above the therapeutic alliance in a study of 66 clients treated with process-experiential psychotherapy or cognitive-behavioural therapy for depression. The measure showed high internal consistency and item-total correlations. Principal-axis factoring, followed by oblique rotation, showed that the measure comprised two factors: (a) behaviour change and (b) awareness and understanding. Clients' CTSC-R scores changed over the course of psychotherapy and predicted change in depression at the end of therapy over and above the therapeutic alliance, explaining an additional 13% of the variance in outcome on the Beck Depression Inventory. Limitations of the study and future directions for research are discussed.

Physical friction is under-recognized as an irritant that can cause or contribute to contact dermatitis

BACKGROUND

The role of physical friction as an irritant in the causation of contact dermatitis is under-recognized. Frictional dermatitis is defined as an eczematous process in which physical frictional trauma contributes to the induction of a dermatitis process.

OBJECTIVES

To examine the clinical background of patients in whom friction was contributing to dermatitis.

METHODS

Over a 30-month period during which 2700 new patients were seen, frictional irritancy was identified as playing a role in the dermatosis in 31 cases: in 27 of these, case notes were evaluated for a range of parameters.

RESULTS

Physical friction was identified as causing or contributing to the dermatitis in 18 men and nine women, mean age at onset 42 years. The hands, usually the fingers of the dominant hand, were affected in all but two cases. Occupational frictional activities were found in 25 cases: commonly handling small metal components, paper, cardboard or fabric, and driving. Potential frictional activities in hobbies were noted in 12 cases. Wet work irritancy contributed in four cases (15%). Patch testing showed relevant contact allergies as cofactors in seven of 25 subjects tested (26%). Psoriasis was a cofactor in four (15%), and atopic dermatitis in 11. The study was selective, being based in a teaching hospital clinic with a special interest in contact dermatitis. Frictional irritancy is often one of several factors contributing to dermatitis.

CONCLUSIONS

The contribution of friction to contact dermatitis is under-recognized probably because dermatologists do not think about the potential for physical forces to induce eczematous changes in the skin.

Environmental tobacco smoke exposure patterns: a subanalysis of the Canadian Human Time-Activity Pattern Survey

This subanalysis of the Canadian Human Activity Pattern Survey examines environmental tobacco smoke (ETS) exposure in non-smoking respondents relative to age, sex, socioeconomic status and prevalence of asthma. 2,381 respondents (response rate 64.5%) from Toronto, Vancouver, Edmonton and Saint John completed a 24-hour recall time-activity diary. For each activity and location, respondents were asked, "was there any smoking during the activity?" Among non-smoking adults, youth, children and asthmatics, the rates of ETS exposure were 32%, 34%, 30% and 42% respectively. Regarding the location of exposure, adults reported ETS exposure in various locations (work, bars and restaurants), including home. Children experienced the most exposure at home, primarily between 4 p.m. and midnight. Adults reported ETS mainly in the living room (16%) and vehicles (13%); for children, the living room (22%) and the bedroom (13%) were the most common locations. Determining characteristic time and location patterns for ETS exposure underpins educational strategies to help non-smokers avoid ETS exposure.

Dental amalgam and multiple sclerosis: a case-control study in Montreal, Canada

BACKGROUND

The aetiology of multiple sclerosis (MS) remains poorly understood. Dental amalgams containing mercury have recently been suggested as a possible risk factor for MS.

METHODS

In a case-control study conducted between 1991 and 1994, we interviewed a total of 143 MS patients and 128 controls, to obtain information on socio-demographic characteristics and the number of dental amalgams and the time since installation based on dentists' records.

RESULTS

Neither the number nor the duration of exposure to amalgams supported an increased risk of MS. After adjustment for age, sex, smoking, and education those who had more than 15 fillings had an odds ratio (OR) of 2.57 (95% CI: 0.78-8.54) compared to those who had none; for individuals whose first amalgam was inserted more than 15 years prior to the study, we found an OR of 1.34 (95% CI: 0.38-4.72).

CONCLUSIONS

Although a suggestive elevated risk was found for those individuals with a large number of dental amalgams, and for a long period of time, the difference between cases and controls was not statistically significant.

Pharmacokinetics of benzo[a]pyrene in the rat

Groups of 4 male Wistar rats were dosed intravenously with 14C-labeled benzo[a]pyrene dissolved in an Emulphor/water vehicle at 3 different dose levels and killed at 1 of 15 specific time intervals from 5 min to 32 h after dosing. 14C-Radiolabel concentration-time data were obtained for blood, brain, adipose, heart, kidney, liver, lung, spleen, and testes. Benzo[a]pyrene concentration-time data were obtained for blood, adipose, kidney, liver, and lung. Appropriate mathematical models were fitted to these data and to the data for metabolites derived as the residuals from 14C-radiolabel minus benzo[a]pyrene difference, where applicable. Nonlinear kinetics were found for 14C-radiolabel in liver, while the data from lung for both 14C-radiolabel and for benzo[a]pyrene per se supported the binding of benzo[a]pyrene in that tissue.

Parental reporting of childrens' coughing is biased

Assessment of cough in the clinical setting as well as in community-based studies of respiratory epidemiology has relied on self-reports. To examine the accuracy and potential for systematic bias in reported cough during a field study, questionnaires administered to parents about their childrens' coughing were compared to overnight cough recordings performed in 145 homes in the community of Wallaceburg, Canada. Percentage agreement between reported and recorded coughing was low, with kappa statistics ranging from 0.02-0.10. Compared to non-smoking parents, smokers under-reported their childrens' coughing (p = 0.01). The association found between parental smoking and recorded coughing was biased towards the null when reported coughing was substituted for recorded coughing: the odds ratio between parental smoking and recorded coughing was 3.1 (95% CI: 1.1-8.8) whereas for reported coughing it was 0.6 (95% CI: 0.2-1.7), the difference in the odds ratios being significant at p = 0.03. When carrying out field surveys, consideration should be given to measuring cough in a subsample of the population in order to estimate the degree of bias inherent in the questionnaire-based results.

Indoor air quality and health: validity and determinants of reported home dampness and moulds

BACKGROUND

Questionnaire-based surveys from several countries have consistently detected adverse health associated with home dampness and mould growth.

METHODS

To test the validity of questions commonly used to indicate the presence of indoor mould, questionnaires were administered in 403 homes where dust samples were taken for viable fungi and air samples for ergosterol.

RESULTS

Geometric mean concentrations of the total viable fungi were 255 (SE 116) x 10(3) CFU/g when mouldy odours were reported and 155 (SE 55) when odours were not reported (P = 0.01). Similarly, reported water damage was associated with a 50% increase (P = 0.06). Geometric mean concentrations of the predominantly indoor-source fungi, Aspergillus plus Penicillium, were twice as high when mould or mildew was reported than when not mentioned (P = 0.01). The presence of reported mould or water damage was unrelated to the presence of detectable levels of ergosterol. There was evidence for reporting bias: in the presence of low concentrations of viable fungi in dust, respondents reporting allergies were more likely to report visible mould growth (odds ratio [OR] = 1.8, 95% confidence interval [CI]: 0.9-3.5, P = 0.10. In the presence of elevated concentrations of dust fungi, respondents who smoked were less likely to report visible mould growth, (OR = 0.4, 95% CI: 0.2-0.7, P = 0.005).

CONCLUSIONS

Reported mould, water damage, and mouldy odours were associated with elevated levels of indoor fungi. However, inaccuracy was high and there was evidence of a systematic reporting bias. Future research should concentrate on developing accurate objective measures of exposure to fungi, and then use this information to develop valid questionnaires. Currently, objective measures not questionnaires, are recommended to clarify the health effects of indoor fungi.

Sensitivity of lungs of aging Fischer 344 rats to ozone: assessment by bronchoalveolar lavage

Biological effects indicators in bronchoalveolar lavage fluid were studied in Fischer 344 rats of different ages after exposure to 0.4-0.8 ppm ozone for periods of 2-6 h on a single day or on 4 consecutive days. The magnitude of alveolar protein transudation induced by ozone was not different between age groups, but the interindividual variability of protein changes was higher in senescent (24-mo-old) rats. By comparison to juvenile (2-mo-old) and adult (9-mo-old) rats, senescent animals had higher increases of interleukin-6 (up to 10-fold higher) and N-acetyl-beta-D-glucosaminidase (NAGA; 2-fold higher) in lung lavage after ozone. Ascorbic acid was lower in lungs of senescent rats (one-half of juvenile values), and acute ozone exposure brought a further decrease in lung ascorbate. Whereas alveolar protein transudation was attenuated after ozone exposure on 4 days, persistent elevation of NAGA in senescent rats suggested only partial adaptation. Injection of endotoxin did not modify the patterns of effects. Incorporation of 18O-ozone into macrophages and surfactant was not different between age groups, indicating that the magnified biological responses in senescent rats were not dominated by differences in internal dose of ozone. The results indicate that senescent rats respond differently than juvenile and adult rats to lung injury.

The Canadian Human Activity Pattern Survey: report of methods and population surveyed

The assessment of health risk due to environmental contaminants depends upon accurate estimates of the distribution of population exposures. Exposure assessment, in turn, requires information on the time people spend in micro-environments and their activities during periods of exposure. This paper describes preliminary results including study methodology and population sampled in a large Canadian survey of time-activity patterns. A 24-hour diary recall survey was performed in 2381 households (representing a 65% response rate) to describe in detail the timing, location and activity pattern of one household member (the adult or child with the next birthday). Four cities (Toronto, Vancouver, Edmonton and Saint John, NB) and their suburbs were sampled by random-digit dialling over a nine-month period in 1994/1995. Supplemental questionnaires inquiring about sociodemographic information, house and household characteristics and potential exposure to toxins in the air and water were also administered. In general, the results show that respondents spend the majority of their time indoors (88.6%) with smaller proportions of time outdoors (6.1%) and in vehicles (5.3%). Children under the age of 12 spend more time both indoors and outdoors and less time in transit than do adults. The data from this study will be used to define more accurately the exposure of Canadians to a variety of toxins in exposure assessment models and to improve upon the accuracy of risk assessment for a variety of acute and chronic health effects known or suspected to be related to environmental exposures.

The effect of different levels of dietary alpha-linolenic and other fatty acids on mammary gland ductular cell proliferation in female Swiss Webster mice

In previous work we have shown that changing the fatty acid composition of a constant amount of fat in a modified AIN-76A diet affected the level of ductular cell proliferation in the mammary glands of young virgin female Swiss Webster mice. In particular, linoleic acid concentrations of 5-10% of the total fat in the diet led to variable but appreciably higher levels of proliferation than did higher levels of linoleic acid. In this report it is shown that feeding low levels of the total fat as alpha-linolenic acid (0-5%) resulted in a similar effect. In addition the effects of other fats including menhaden oil, were further investigated.

The effect of butylated hydroxytoluene on the growth of enzyme-altered foci in male Fischer 344 rat liver tissue

Butylated hydroxytoluene (BHT) is a synthetic, food-use, phenolic antioxidant. It has previously been demonstrated to be operationally non-genotoxic and, in addition, failed to induce biologically significant increases in cellular proliferation in the liver, urinary bladder and thyroid gland on feeding to young adult Wistar rats. Nevertheless, it has been reported to enhance the yield of liver tumors when fed to rats or mice that developed an appreciable background incidence of these tumors without treatment. In order to resolve this situation, cell proliferation in response to BHT treatment was studied in enzyme-altered foci (EAF) induced in male Fischer 344 rats using the Solt-Farber procedure. It was demonstrated that feeding 0.5% dietary BHT for 30 days after the induction of EAF led to a 20- to 30-fold increase in the gamma-glutamyltranspeptidase-positive areas in both DEN- and saline-initiated rat livers, but to no major effects in glutathione S-transferase placental form (GSTP)-positive foci. Cell proliferation rates within EAF and surrounding normal liver were measured using different histological techniques. Nuclear labeling with [3H]thymidine and proliferating cell nuclear antigen (PCNA) over the total hepatocyte population indicated that BHT approximately doubled nuclear labeling in rats initiated with DEN. PCNA labeling in GSTP-positive foci was not affected by BHT. In GSTP-positive foci, evaluation of nucleolar organizer regions (AgNOR), which reflect cell proliferative in addition to transcriptional activity of ribosomal RNA, was achieved using a novel double staining technique. BHT diet did not affect the number of AgNOR per nucleus or the percentage AgNOR area/nucleus. Nevertheless, both PCNA labeling and the AgNOR area per nucleus were significantly greater in GSTP-positive foci compared with non-focal regions in rats fed either BHT or control diets. These results are discussed in the light of further experimental work required to determine the relevance of these data to possible human risk assessment for BHT.

Effect of addition of dried healthy or diseased parsnip root tissue to a modified AIN-76A diet on cell proliferation and histopathology in the liver, oesophagus and forestomach of male Swiss Webster mice

Umbelliferous crop plants, including the parsnip (Pastinaca sativa L.), elaborate enhanced levels of furocoumarins, including psoralens, when subjected to biotic or abiotic stress. These furocoumarins are recognized to lead to phototoxicity. In this study, the effect of these agents, which are present in diseased parsnip root tissue, on the liver and two tissues on the route of entry to the body (the oesophagus and forestomach) were investigated. Young male Swiss Webster mice were fed for approximately 30 days with modified AIN-76A diets containing 32.5% dried healthy, 32.5% apparently healthy or 32.5% fungicide-treated parsnip root tissue, and 8, 16 or 32.5% dried diseased (Phoma complanata-infected) parsnip root tissue. As controls, three modified AIN-76A diets differing in their edible starch-to-sucrose ratios (C1-C3) were administered for an equal time. Dried healthy parsnip root tissue, compared with controls, did not significantly affect any of the indices of cellular proliferation or histopathological parameters that were assessed. Histopathological examination of the oesophagus and forestomach demonstrated no significant changes as a result of feeding any of the diets containing parsnip tissue. In the liver, the highest level (but neither of the two lower levels) of dried diseased parsnip root tissue led to swelling of the cytoplasm in cells surrounding the central vein of hepatic lobules, with consequent compression of the peripheral cells. Using [3H]thymidine radioautography, a dose-related increase in cell labelling with the level of diseased parsnip root tissue was demonstrated in the liver. Compared with control diet C2 only, the extent of [3H]thymidine labelling in the liver was increased in mice receiving apparently healthy parsnip tissue; a slight, not statistically significant, increase was also noted with fungicide-treated parsnip tissue. Increased [3H]thymidine labelling with the feeding of diseased parsnip tissue was also found in the greater curvature of the forestomach and the region of the oesophageal-forestomach junction, but not at the glandular junction of the forestomach nor in the mid-oesophagus.

Levels of chlorinated hydrocarbon residues in Canadian human breast milk and their relationship to some characteristics of the donors

A total of 412 breast milk samples from women in all provinces of Canada were analysed for polychlorinated biphenyls, eight chlorinated benzenes, 2,3-dichloronaphthalene, Mirex, alpha, beta, gamma and delta hexachlorocyclohexane, alpha and gamma chlordane, oxychlordane, transnonachlor, p,p'-DDT and some analogues, heptachlor epoxide, dieldrin and octachlorostyrene. No delta-hexachlorocyclohexane, heptachlor or aldrin were found in any of the samples, while median levels of the 1,2,4- and 1,3,5-trichlorobenzene, 1,2,3,4- and 1,2,3,5-tetrachlorobenzenes, gamma chlordane, o,p'-DDT and octachlorostyrene were all less than the minimum detectable level (MDL). All other compounds were present at median levels ranging from < 0.1 to 7.2 ng/g whole milk, but did not occur in all samples. Di to tetrachlorobenzenes, except 1,2,4-trichlorobenzene, 2,3-dichloronaphthalene and alpha-chlordane were observed in < 50% of the samples. From 1967 to 1986 a steady decline of hexachlorobenzene, gamma-hexachlorocyclohexane, DDTs, heptachlor epoxide and dieldrin was observed in Canadian breast milk. In addition, a decrease in some chlorinated benzenes, gamma-hexachlorocyclohexane and PCBs was also observed between 1982 and 1986. Levels of oxychlordane and trans-nonachlor remained constant. Canadian breast milk contamination appears to be one of the lowest among the industrialized nations. Regional and provincial differences in residue levels appeared minimal, although more often samples from Quebec and British Columbia had higher levels of some contaminants, such as oxychlordane, than samples from other provinces. No relationship was found between maternal age and residue levels, but some contaminants, such as PCBs, were significantly higher in the milk of mothers who breastfed their first child as compared to multiparous mothers. Breast milk residue levels were not related to fish consumption.

Effect of varying the type of fat in a semi-purified AIN-76A diet on cellular proliferation in the mammary gland and intestinal crypts in female Swiss Webster mice

Young virgin female Swiss Webster mice were fed AIN-76A semi-purified diets containing equal weights of different fats for approximately 30 days. Using [3H]thymidine radioautography, it was established that mice fed 100% lard or high levels of fish oils (menhaden oil or cod liver oil) developed elevated cellular proliferation in the duct cells of the mammary gland and an increased number of labeled cells/crypt in the crypts of the colo-rectum accompanied by an increase in the size of the proliferative compartment. A possible inverse correlation between the level of [3H]thymidine labeling in the mammary gland, but not in the colo-rectum, and the linoleic acid content of individual diets may help to explain the significance of these observations. The effect of adding an antioxidant mixture to these diets was to reduce the excess proliferation induced in the intestinal crypts by lard or fish oil to the level induced by soybean oil, but only partially so in the duct cells of the mammary gland.

Liver DNA adducts in methyl-deficient rats administered a single dose of aflatoxin B1

Using an 8 week Solt-Farber protocol with selection pressure (2-acetylaminofluorene/partial hepatectomy) applied during weeks 6 and 7, we have observed that a single oral administration of aflatoxin B1 (AFB1) to Fischer 344 rats on day 1 of the study, followed by a 3 week feeding regimen of either a methyl-deficient (CMD) or a basal (CMS) diet, results in a relative increase in hepatic preneoplastic lesions in CMD diet fed rats. It has previously been shown that a multiple dosing regimen with AFB1, started after 3 weeks of CMD diet, enhances tumor incidence. In the present study, the role of metabolic activation in the induction of preneoplastic lesions, and liver DNA adduct levels after the first dose of AFB1 in the tumorigenesis model have been investigated. AFB1-DNA adducts were determined at 2-168 h following a single non-necrogenic (100 micrograms/kg body wt) or necrogenic (600 micrograms/kg body wt) dose of AFB1 on day 1 or day 21 of a 3 week treatment with a complete basal or CMD diet. In all rats irrespective of dose, dietary treatment or time of AFB1 dosing, the patterns of adduct formation and repair did not change. In rats receiving AFB1 on day 1, total DNA adduct levels between the diet or dose groups were not significantly different, and quantitatively did not correlate with the observed increase in preneoplastic lesions, suggesting a contribution by additional factors in the initiation of these lesions. Administration of AFB1 on day 21, however, resulted in significantly reduced levels of total adducts at both dose levels in CMD diet fed rats compared to controls. Serum biochemistry data suggest that a prolonged exposure to CMD diet may cause pathological and/or biochemical alterations in hepatocytes with a resultant decrease in metabolic activation of AFB1, thus making it difficult to evaluate whether DNA damage is directly related to tumorigenesis.