blood and tooth lead levels
TRANSCRIPT
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GOOD MORNING
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PROLOGUE
y Lead is a heavy, soft, toxic, gray-blue metal which occurs naturally
as trace element in the earth's crust.
y When ingested, inhaled, or absorbed through skin, lead is highly
toxic to humans.
y Lead's toxicity has been known for thousands of years; Greek
physicians made the first clinical description of lead poisoning inthe first century B.C.
y It persists in the soil, in the air, in drinking water, and in homes.
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PROLOGUE
Lead accumulates where it is deposited and can poison generations
of children and adults unless properly removed.
At high levels, lead poisoning causes coma, convulsions and death.
At low levels - lead poisoning in childhood causes reductions in IQ
and attention span, reading and learning disabilities, hyperactivity,
impaired growth, behavioral problems, and hearing loss.
These effects are long-term and may be irreversible.
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PROLOGUE
y Exposure to lead can be evaluated by measuring lead in blood, teeth,
hair, and bone which are then used to estimate body lead burden.
y Most studies looking at lead exposure among children have used
Blood lead (BPb) levels as a marker of exposure.
Disadvantage: Lead in the blood has a short half-life of 30 days and
reflects recent exposure and, therefore, is of limited value in
predicting neurotoxicity
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PROLOGUE
y Teeth accumulate lead over a long period of time and provide an
integrated record of lead exposure from intrauterine life until the
teeth are shed.
Advantage :
1. Dental hard tissues are relatively stable, metals deposited in teeth
during mineralization are, to a large extent, retained.2. There is no turnover of apatite in teeth ,therefore it is the most
useful for studying past lead exposure.
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Justification for selecting the article
y There are varying results seen from the previous studies conducted in
relation to this topic.
y The present study has good public health significance and provides aninsight of the various ill effects caused by lead especially among children.
y The article tries to emphasize the importance of using bio indicator like
primary teeth which are better predictors of lead toxicity than
conventionally used blood samples to estimate lead content.
y Chronic lead poisoning manifests in oral cavity as Burtonian line is of
significance to dentists in identifying the chronic lead poisoning.
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ABOUT THE JOURNAL
Journal
:International Journal of Pediatric Dentistry
International journal
Peer reviewed journal Features of journal
Indexed journal Publisher : Blackwell Publishing Ltd
ISSN number : 0960-7439 (print)
:1365-263 X (online)
Impact factor :1.289 [2010]
Periodicity : Bi-monthly [ Six issues per year]
MeSH representation: Int J Paediatr Dent
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ABOUT THE ARTICLE
Yearofpublication : 2010
Volumenumber: 20
Pagenumber:186-192
Receivedon: -
Accepted on : -
Dateof Issue:11-11-10
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ABOUT THE AUTHORS
Sapna Hegde,
Mukthineni Sridhar
Dinesh Rao Bolar
Shubha Arehalli Bhaskar
Mitesh Bharat Sanghavi
AFFILIATION: Department of Pediatric Dentistry, Pacific Dental
College & Hospital, Udaipur, Rajasthan, India.
Address and e-mail of first author [Dr. Sapna Hegde] has been
provided for future correspondence
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TRACK RECORD OF THE AUTHORS
Sapna Hegde 8 studies
Mukthineni Sridhar 1 study
Dinesh Rao Bolar 1 study
Shubha Arehalli Bhaskar 1 study
Mitesh Bharat Sanghavi 1 study
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CRITICAL APPRAISAL OF THE TITLE
Relating tooth- and blood-lead levels in children residing near
a zinclead smelter in India
Title looks interesting.
Title is neither too short nor too long comprising of16 words
Indicates the focus of the study.
Title is neither too specific nor too general.
Title is meaningful but incomplete as the study setting is not mentioned
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CRITICAL APPRAISAL OF THE TITLE
Study design is not mentioned in the title.
Title indicates both dependent and independent variables
y Independentvariable:Exposure to zinc and lead from a smelter
y Dependentvariables:Tooth and blood lead levels
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PROPOSED ALTERNATIVE TITLE
Relationship between tooth and blood Lead levels in 5-13 year olds
residing near a Zinc-Lead smelter in India- A cross sectional study.
[ 22 words]
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CRITICAL APPRAISAL OF THE ABSTRACT
It is a structured abstract.
It is an informative and comprehensive abstract.
Abstract comprises of 200 words.
Abstract gives the gist of the whole text .
Information in the abstract matches with that present in the text.
It contain acronyms that are expanded at its first occurrence
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CRITICAL APPRAISAL OF THE KEYWORDS
y It has a subheading Design which seems to be inappropriate;
instead the subheading should have been Methodology
y Key words : Providing keywords is not feature of this journal.
Proposed key words:
Tooth , blood lead levels , India 1st article
Tooth , blood lead levels , India, Children 1st article
Tooth , blood lead levels 3rd article
MeSH terms : Tooth , Lead , Child , Zinc
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CRITICAL APPRAISAL OF INTRODUCTION
Introduction is meaningful.
Phenomenon of interest is clearly mentioned.
It is built on existing literature.
It is written in a seminar approach.
It is logically presented.
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CRITICAL APPRAISAL OF INTRODUCTION
Current knowledge related to the present study have been stated by
quoting relevant studies.
The authors have quoted the need for the study, it is implicitly
implied in the following lines as
- In India, several studies have been undertaken to determine the BPb level, but
data pertaining to tooth-lead (TPb) level is lacking. The correlation between TPb
and BPb levels has not received sufficient attention.
How relevant and valid are these reasons for conducting this study?
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CRITICAL APPRAISAL OF INTRODUCTION
y Research question, null hypothesis and research hypothesis are not
mentioned.
PROPOSED RESEARCH QUESTION
Is there a relationship between tooth and blood lead levels in
5-13 years old children residing near a zinc lead smelter in India ?
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CRITICAL APPRAISAL OF INTRODUCTION
PROPOSED ALTERNATIVE HYPOTHESIS [ H1]
There exists a relationship between tooth and blood lead levels in
5-13 years old children residing near a zinc lead smelter in India.
PROPOSED NULL HYPOTHESIS [ H0]
There exists no relationship between tooth and blood lead levels in
5-13 years old children residing near a zinc lead smelter in India.
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MATERIALS AND METHODS
100 children wereselected.
Five villages located within aradius of four Km from the
Zinclead smelter
Based on age and time of toothexfoliation subjects weredivided into three groups:
(i) 58 years (ii) 911 years(iii) 1213 years.
Each of these children had atleast one healthy primary
tooth nearing exfoliation orrequiring extraction fortherapeutic purposes.
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MATERIALS AND METHODS
Analysis of blood lead and tooth lead levels
y Hundred primary teeth were collected from the study subjects.
y Tooth was treated using 3% hydrogen peroxide solution to remove
organic material. Then, 3 ml of 70% HNO3
and 70% perchloric acid
was used to dissolve the tooth for lead estimation .
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MATERIALS AND METHODS
y Two milliliter of venous blood was collected from the subjects and
transferred to a lidded glass vial.
y Reagent ethylene diamine tetra acetic acid, which binds to lead in
blood and facilitates its separation, was added in equal volume to
collected blood
y Lead levels in tooth and blood was determined using Flame Atomic
Absorption Spectrophotometer (AAS) with electrothermal
atomization.
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STATISTICAL ANALYSIS
y Statistical analysis was done using SPSS-15 software.
yGroup wise comparison between males and females was carried out
using Students t-test.
y Analysis of Variance (ANOVA) was used to assess group wise
comparison based on tooth type, age, and village.
y A critical value of P < 0.05 was considered statistically significant.
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CRITICAL APPRAISAL OF MATERIALS AND METHODS
Written informed consent was obtained from the parents - Not clear
whether it is for collection of only the primary tooth
Methodology is lucidly presented with respect to:
- Method of collecting blood and analyzing the lead level in it.
- Method of processing the tooth to assess the lead content in it.
Product detail of Flame Atomic absorption Spectrophotometer is
mentioned, however it is not mentioned for chemical reagents used.
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CRITICAL APPRAISAL OF MATERIALS AND METHODS
Was ethical clearance obtained for conducting the study?
Was assent obtained from children?
It is not clear whether the Sample size was scientifically determined.
The method of selecting the five villages and the children from each
village is not described.
Study setting has not been mentioned
Statistical tests used in the study are not appropriate for the set
objectives.
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RESULTS
VillageDistancefrom Pbsource(km)
N
Mean SD
BPb TPbDifference P
1 0.5 9 15.11 5.62 33.68 22.59 18.75 0.034*
2 2.0 17 7.59 4.36 29.66 23.28 22.07 0.001**
3 2.5 48 6.58 5.26 43.13 30.48 36.55 0.000**
4 3 14 6.36 4.52 51.55 66.58 45.20 0.027*
5 4 12 10.25 5.33 50.49 25.87 40.24 0.000**
BPb, blood lead; TPb, tooth lead.*Significant.
**Highly significant.
Table 1. Intra-village comparison of BPb and TPb levels (g dL).
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RESULTS
d.f. Sum of squares
Meansquare
F P
BPb 4 65.37 16.09 6.36 0.000*
TPb 4 54.47 13.86 1.05 0.38
BPb, blood lead; TPb, tooth lead.
*Highly significant.
Table 2. Comparison by village of BPb and TPb levels.
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RESULTS
Village Village Mean differenceBPb
P
1 2 7.52 0.001**
3 8.53 0.000**
4 8.75 0.000**5 4.86 0.032*
2 3 1.00 0.484
4 1.23 0.502
5 2.66 0.167
3 4 0.23 0.883
5 3.67 0.027*
4 5 3.89 0.054
BPb, blood lead.
*Significant.**Highly significant.
Table 3. Inter-village comparison of BPb levels.
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RESULTS
Sex N MeanSDBPb TPb
Difference P
Male 67 8.19 5.69 40.02 38.99 31.83 0.000*
Female 33 7.39 5.41 46.18 28.31 38.78 0.000*
BPb, blood lead; TPb, tooth lead.*Highly significant
Table 4. Intra-group comparison of BPb and TPb levels based on gender.
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RESULTS
Tooth type N Mean SDBPb TPb
Difference P
Primary incisors 36 8.17 5.42 40.67 21.06 32.50 0.000*
Primary canines 29 6.79 5.1 46.77 50.10 39.98 0.000*
Primary molars 35 8.63 6.11 39.56 34.33 30.94 0.000*
BPb, blood lead; TPb, tooth lead.*Highly significant.
Table 5. Intra-group comparison of BPb and TPb levels based on tooth type.
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RESULTS
Agegroups(years)
N Mean SDBPb TPb
Difference P
5-8 36 8.14 5.46 38.96 20.82 30.82 0.000*9-11 46 7.65 5.82 44.85 45.37 30.720 0.000*
12-13 18 8.22 5.48 41.08 32.80 32.86 0.001*
BPb, blood lead; TPb, tooth lead.
*Highly significant.
Table 6. Intra-group comparison of BPb and TPb levels based on age.
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CRITICAL APPRAISAL OF RESULTS
Results are not based on the objectives of the study Correlation
between tooth and blood lead levels was not found using appropriate
statistical test.
Results are presented in logical manner in both tables and text.
Tables are numbered and titled appropriately.
Foot notes are present for all the tables.
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CRITICAL APPRAISAL OF RESULTS
All tables show inferential data.
In table 3, post hoc test has been used. Which post hoc test was used
is not mentioned in the Methodology section as well as in Results
section.
Unit of measurement for blood and tooth lead levels is not presented
in tables 2, 3, 4, 5 and 6.
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CRITICAL APPRAISAL OF DISCUSSION
Discussion is meaningful.
There is justification given for the following:
I. Why blood lead levels were used ?
II. Why primary tooth has been taken for comparison?
III. Why Atomic Absorption Spectrophotometry has been used to
estimate blood levels?
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CRITICAL APPRAISAL OF DISCUSSION
y The findings of the present study are:
I. Villages 1 and 5 had mean BPb level greater than 10g/dl , which
is thelevel of concern as given by the CDC and the OSHA.
II. Blood-lead and TPb levels do not seem to depend on gender.
III. No association was seen between TPb and age.
Results of the present study have been explained in comparison
with other studies.
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CRITICAL APPRAISAL OF DISCUSSION
The authors have given logical explanation for the study findings.
There is mention of limitations of the study.
Discussion has gradually tapered down to conclusion.
Scope for further studies has been mentioned.
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CRITICAL APPRAISAL OF CONCLUSIONS
y Conclusions are not based on the set objectives. They are extended
conclusions.
y Conclusions highlight the following findings:
1.Blood-lead concentration was higher in children residing in closer proximity to the
zinclead smelter, whereas TPb was not influenced by minor increase decrease in
distance from the lead source within the area of the study.
2. The BPb concentrations were independent of age and sex while, TPb concentrations,
although significantly higher than the BPb levels, was independent of age, sex, and
tooth type.
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CRITICAL APPRAISAL OF CONCLUSIONS
3. The TPb level being significantly higher than BPb level is indicative of the
cumulative exposure to lead as against the BPb which reflects recent exposure.
Hence, TPb can be considered a better biologic indicator of the overall exposure
4. No consistent pattern of correlation existed between the BPb and TPb levels in the
population studied.
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Conclusions are not appropriate because apt statistical tests are not
employed( correlation coefficient tests).
Need for further research has been explicitly mentioned in following
lines:
More studies with larger sample sizes, using more homogenous and standard
parameters and in different ethnic populations of India are needed to substantiate
the results of the present study.
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CRITICAL APPRAISAL OF REFERENCES
References have been made for all the citations in the text part of the
article.
Non -accessible references are 7, 10, 11,13,14,17,19 and 22.
References are accurate. All references are in English.
References have been presented according to Vancouver system of
referencing.
All accessible references are primary references.
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CRITICAL REFLECTION
Thepresentstudyresultscannotbegeneralizedbecause:
Sample size is not scientifically justified
Subjects were not randomly selected from the population
Thestudyhasgoodpublichealthsignificance.
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PUBLIC HEALTH SIGNIFICANCE
y Tooth lead levels can be a better biologic indicator of exposure tolead during early life as it levels are due to accumulation over periodof time .
y
Tooth lead levels provide a readily accessible bone biopsy , so canact as proxy measure for skeletal lead levels.
y Tooth lead levels are more stable than the blood lead levels andshow little variations , hence can be appropriate estimate of lead
toxicity especially in children.
y Lead toxicity has become a major public health problem in thedeveloping countries due to overexposure to lead in theenvironment.
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PUBLIC HEALTH SIGNIFICANCE
y More severe and debilitating effects are seen in the children as they
are in growing phase and also have more ability to absorb and retain
lead resulting in lead poisoning.
y Lead also has ability to effect fetus as they can pass easily throughplacenta resulting in neurotoxicity and malformations .
y Blood lead levels in children of around 10 g/dl are associated with
disturbances in early physical and mental growth and in later intellectual functioning and academic achievement. These persist
into adulthood and may be irreversible
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PUBLIC HEALTH SIGNIFICANCE
y The World Health Organization estimates that 15-18 million
children in developing countries are suffering from permanent brain
damage due to lead poisoning.
y The US Center for Disease Control and Prevention (CDC) has set alevel of concern for children at 10 g dL. However, studies have
provided evidence of the possibility of very harmful effects at even
levels of exposure as low as 5 g dL. Hence, no level of lead
exposure can be considered safe enough.
y Primary tooth lead level estimation can be an effective procedure
for estimating of lead concentration among children and to take
necessary steps to prevent further lead related ill-effects.
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HIERARCHY OF EVIDENCE
The present study fits into this level in the
hierachy of evidence.
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