Blood and Tooth Lead Levels

8/3/2019 Blood and Tooth Lead Levels

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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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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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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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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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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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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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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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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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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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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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Documents

Blood and Tooth Lead Levels