1. PRACTICUM 2016
• OIL AND GAS WELL ACTIVITY AND COMMERCIAL MOTOR VEHICLE-RELATED CRASH FATALITY RATES IN TEXAS
• FLUORIDATION CESSATION AND DENTAL CARIES
• PUBLIC HEALTH FIELD WORK IN BRUNI TEXAS
Tariq Nisar M.P.H. Epidemiology & Biostatistics
2. Background
Objective
Methods
Variable Characteristics
Descriptive Statistics
Exploratory Analysis
Statistical Approach
Discussions
OIL AND GAS WELL ACTIVITY AND COMMERCIAL MOTOR VEHICLE-RELATED CRASH FATALITY RATES IN
TEXAS
3. OIL AND GAS WELL ACTIVITY AND COMMERCIAL MOTOR VEHICLE-RELATED CRASH FATALITY RATES IN
TEXAS
In United States : Oil & Gas extraction is growing with almost 380,000
workers.
During 2003-2006 : An increase of 15% in fatalities were recorded
(Department of Labor’s Bureau of Labor Statistics).
CFOI ( Census of Fatal Occupational Injuries) revealed : Rate of fatality is
correlated with increase in the activity of oil & gas extraction
Ref: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5716a3.htm
4. During 2003-2006: Annual fatality rate was 30.5 per 100,000 workers
(7 times more)
Most common injuries: High-way motor vehicle crashes (27%) &
Workers injured by tools / equipment’s (22%).
Texas: 38%
Louisiana: 12%
Oklahoma: 11%
Wyoming: 8%
New Mexico : 5 %
Ref: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5716a3.htm
5. Texas : Highest volume producer of crude oil and natural gas
Since 2005 : Number of Oil well workers have doubled
The U.S. Occupational Health & Safety Administration (OSHA) : 40 % of
work related fatalities are motor vehicle fatalities
Ref:
1: http://www.eia.gov/naturalgas/crudeoilreserves/
2: Rahm, D., Fields, B., and Farmer, J. L. (2015). Transportation Impacts of Fracking in the Eagle Ford Shale Development in Rural South Texas:
Perceptions of Local Government Officials. Journal of Rural and Community Development.
STATE OF TEXAS
6. OBJECTIVE
To examine the characteristics of commercial motor vehicle (CMV)-
related crash fatalities in Texas
To identify measure of associations between the amount of oil & gas
activity and CMV crash fatalities rates in Texas counties
7. METHODS
Data : 2012-13 CMV – related crash fatalities from TXDOT or
Texas DSHS. TXDOT traffic collision data were linked with
DSHS EMS & Trauma Registries injury surveillance data
Border adjacency & Urbanization status were determined
according to DSHS center for health statistics indicators
Texas county population data : United States Decennial
Census for 2010 & used to estimate person-years for the
years 2012-2013 (5)
Active oil and gas well counts : Texas Railroad Commission.
Texas counties were categorized by quartile of average
active well count during September 1, 2011-August 31, 2013
Ref: Oil and gas well activity and commercial motor vehicle-related crash fatality rates in Texas
Emily Hall, MPH, Natalie Archer, PhD, Tariq Nisar, Nina Leung, PhD
Texas Department of State Health Services
8. CHARACTERISTICS OF VARIABLES
Continuous Variables : Total deaths, person year, average number of
wells, & average of total vehicle miles travelled
Categorical Variables : Sex (male & female), Urbanization Status (rural &
urban), Border Status (Non border & Border), and, Well quartiles.
Outcome Variable : Total deaths
9. DESCRIPTIVE STATISTICS
A
Variable Sum Mean Median Standard
Deviation
Total Deaths 891 3.50 2.00 5.35
Person Years 50291122 198000.00 36760.00 705783.6
Average of
Wells
401494.7 1581.00 799.20 2186.78
Average of
Total Vehicle
Miles
travelled
659873606 2598000 772200 8401465
Continuous variables
10. Categorical variablesB
Variable Category Total Deaths Percentage of
Total Deaths
Sex Male
Female
727
164
81.6%
18.4%
Urbanization
Status *
Urban
Rural
522
369
58.6%
41.4%
Border Proximity Border
Non-Border
104
787
11.7%
88.3%
Well Quartiles 1
2
3
4
202
148
259
282
22.7%
16.6%
29.1%
31.6%
11. Well Quartiles Mean Wells (Min & Max) Total Wells in Quartiles
1 20 (0-127) 1268
2 441(130-194) 27808
3 1277(803-1947) 81728
4 4614 (1963-13207) 290690
C Description of Well Quartiles
Ref: Oil and gas well activity and commercial motor vehicle-related crash fatality rates in Texas
Emily Hall, MPH, Natalie Archer, PhD, Tariq Nisar, Nina Leung, PhD
Texas Department of State Health Services
13. NORMALITY ASSUMPTION
The assumption was determined by plotting histograms for outcome variable (Total Deaths)
Interpretation
• The outcome variable i.e.
Total Deaths is not
normally distributed.
• Skewness is towards the
right side of the
histogram.
14. NORMALITY ASSUMPTION CONTD.
The next step was plotting a histogram of log transformed total deaths
Interpretation
• Even After transformation
the outcome variable i.e.
Total Deaths is not
normally distributed.
• Skewness still exists
towards the right side of
the histogram
15. PRINCIPAL COMPONENT ANALYSIS
Invented by Karl Pearson in 1901
Statistical Method : Uses Orthogonal transformation that converts
correlated variables into a set of linearly uncorrelated variables
Number of components < = Number of original variables
First component : Largest variance
16. PRINCIPAL COMPONENT ANALYSIS
PCA: Person years (First component) maximum variance of 0.95
Average Wells (Second component) additional variance of 0.015
Person year was highlighted the most due to higher standard deviation
17. STATISTICAL APPROACH :NON PARAMETRIC MANN-WHITNEY TEST
Groups Total number of deaths
in %
P value
Border Vs Non-Border
Border
Non Border
11.7%
88.3%
0.370
Rural Vs Urban
Rural
Urban
41.4%
58.6%
<0.0001
Well Quartiles * Post
Hocc Analysis
1
2
3
4
22.7%
16.6%
29.1%
31.6%
Quartiles 3 & 4 were
significant with a p
value<0.0014
Sex Males Vs Females
Males
Females
81.6%
18.4%
<0.0001
18. STATISTICAL APPROACH : NEGATIVE BINOMIAL MODEL
Quartile 1 : Reference group
Well quartile 2: [Not Statistically Significant]
Well quartile 3: The expected total number of deaths for quartile 3 is 1.43
times more than the expected total deaths for quartile 1
Well quartile 4: The expected total number of deaths for quartile 4 is 1.7
times more than the expected total deaths for quartile 1
19. Urbanization Status : Reference group
The expected total number of deaths for urban areas is 0.54 times less
than the expected total deaths for rural areas
No difference were observed in fatality rates between counties located
on border and those not located on the border
20. Variables Coefficient-estimates P value
Quartile 2 1.10 0.591
Quartile 3 1.43 0.035 **
Quartile 4 1.70 0.002 **
Urbanization Status
(Urban)
0.54 <0.001 **
Border Status (Non-
Border)
0.944 0.755
21. DISCUSSIONS
First Study : That linked data from TXDOT, EMR, & ETR to examine the
crashes
Results indicated : CMV related crash fatalities in Texas is strongly
associated with active oil & gas wells
Prevention Campaign is required in Rural counties due to higher crash
fatality rates
Ref: Oil and gas well activity and commercial motor vehicle-related crash fatality rates in Texas
Emily Hall, MPH, Natalie Archer, PhD, Tariq Nisar, Nina Leung, PhD
Texas Department of State Health Services
22. DISCUSSIONS
Other preventive campaigns
TXDOT : Changing the behavior of drivers
NIOSH : On going research (Prevention initiatives among CMV drivers)
Other states : Imposed tariffs on vehicles exceeding a certain weight
limit ; Oil & gas company to pay for road maintenance
Further research should be conducted on other factors like
environmental conditions
Ref: Oil and gas well activity and commercial motor vehicle-related crash fatality rates in Texas
Emily Hall, MPH, Natalie Archer, PhD, Tariq Nisar, Nina Leung, PhD
Texas Department of State Health Services
23. FLUORIDATION CESSATION & DENTAL CARIES
A. Fluoride as an element
B. Anatomy of tooth
C. Types of Caries
D. Mechanism of Action of Fluorides
E. Optimal level of Fluorides in drinking water
F. Literature on Fluorides
G. Current Fluoride supplements
25. Bacteriostatic effect
Elimination : Kidney
Inhibit the formation of Dental Caries
CDC reports : Fluoride as top 10th achievements in the field of public
health
26. FLUORIDE : AS HAZARD?
High doses
A : Hypo mineralization of enamel
(during enamel formation) / Enamel
Mottling
B : Skeletal Fluorosis
C: Reversible Gastric Disturbances
D: Death
Chronically Low doses
A : Dental Caries *
28. ANATOMY OF ENAMEL
Hardest substance in the human body
Formed during the Cap Stage of tooth development
96% water & 4% organic material
Primary Mineral : Hydroxyapatite crystal [Calcium Phosphate]
30. MECHANISM OF ACTION OF FLUORIDES / CARIOSTATIC EFFECT
Hydroxyapatite crystals (CalO(P04)6(OH)2) : allows
substitution of minerals within the lattices
The calcium ion of the hydroxyapatite crystals is
replaced by fluoride ion : Flour-apatite crystals
The solubility of flour-apatite (pKsp = 120.215)
:accelerates the precipitation of the apatite mineral
creating a cariostatic environment
Ref: A: Ten Cate, J. M., & Featherstone, J. D. B. (1991). Mechanistic aspects of the interactions between fluoride
and dental enamel. Critical Reviews in Oral Biology & Medicine, 2(3), 283-296
B: Modern Dental Assisting 8th Edition Doni. L Bird & Debi S Robinson : Elsevier copyrights
31. FLUORIDATION
Fluoridation is adding fluorides in drinking water to an optimum level
that is beneficial for preventing tooth decay
Optimal level (U.S. public health services) : 0.7mg/ L (1 to 1.5 ppm)
Ref: Texas Groundwater Protection Committee Meeting TCEQ October 21, 2015 Deba P. Dutta, Emily Hall
32.
33. LITERATURE ON FLUORIDES
Study I : “Pattern of Dental Caries following the cessation of water fluoridation”
Objective : Incidence & prevalence of caries between the cessation of fluoridation and
fluoridated communities in British Colombia
Methods: Children’s examined at baseline & follow up surveys.
Study design : Cross-sectional survey along with longitudinal investigation.
Statistical Model : Multiple Regression (D1D2MFS)
Results : “The prevalence of caries decreased over time in the fluoridation ended
community while remaining unchanged in the fluoridated community.
Ref: Maupomé, G., Clark, D. C., Levy, S. M., & Berkowitz, J. (2001). Patterns of dental caries following the cessation of water
fluoridation. Community Dentistry and Oral Epidemiology, 29(1), 37-47
34. Study II :“The Effects of a Break in Water Fluoridation on the Development of
Dental Caries and Fluorosis”
Objective : Development of dental caries and fluorosis in children’s.
Methods: Fluorosis was recorded in children in cohorts 1 through 5 and caries
was recorded in children in the birth cohort through cohort 3
Study design : (Durham, NC) The water was fluoridated since 1962, but there
was cessation of fluorides for 11 months between September 1990 & August
1962
Statistical Model : Regression
Results :There was 44 % of overall fluorosis during the period when fluorides
were supplemented in the water
Ref: Burt, B. A., Keels, M. A., & Heller, K. E. (2000). The effects of a break in water fluoridation on the
development of dental caries and fluorosis. Journal of dental research, 79(2), 761-769.
35. Study III : “Measuring the short term impact of fluoridation cessation on dental
caries in Grade 2 children using tooth surface indices
Objective : short term impact of cessation of fluorides on children’s caries
Methods: Pre-cessation and post cessation data was collected from the samples
of school going children's in Calgary & Edmonton
Study design : Pre-post cross sectional design.
Statistical Model : Regression & Poisson
Results :an increase in the caries cases with fluoridation cessation that was
statistically significant for both Calgary and Edmonton
Ref:McLaren, L., Patterson, S., Thawer, S., Faris, P., McNeil, D., Potestio, M., & Shwart, L. (2016). Measuring the
short‐term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface
indices. Community dentistry and oral epidemiology, 44(3), 274-282.
36. Study IV : A report on “Effective use of fluorides for the prevention of dental
caries in the 21st century: the WHO approach”
Objective : Systemic review data sets on water fluoridation were summarized by
WHO
Conclusions :
A: Water fluoridation reduces prevalence of dental caries by 15%
B: No evidence of adverse effects of fluorides in drinking water
Recommendations: Maximum fluoride level in drinking water should be 1.5 mg/l
Ref: Petersen, P. E., & Lennon, M. A. (2004). Effective use of fluorides for the prevention of dental caries in the
21st century: the WHO approach.Community dentistry and oral epidemiology, 32(5), 319-321.
38. PUBLIC HEALTH FIELD WORK IN BRUNI TEXAS
Primary purpose: For investigation of Arsenic in Water
Assisted in collecting urine samples
Assisted in collecting water samples from private wells
Remarks:
A: The field trip has given me a great experience in collecting the data
through the questionnaire, educating the people about the purpose of
the investigation, motivating them for participation and managing
things in an orderly fashion.
B : I would like to thank all the members of DSHS staff for letting me
join their team and special thanks to my preceptor Ms. Emily Hall for
supporting me, and giving me hands-on experience with this field trip.
