there has been an increasing frequency of cardiovascular disease ( cvd ) fatal report in developing countries and cvd remained a major and the first public health thread in iran ( 13 ) .
several studies have shown the significant relevance of cvds and air pollution parameters such as pm10 and pm2.5 ( 47 ) and other air pollutants such as nox , so2 , co and o3 ( 811 ) and heavy metals like lead , mercury , selenium , cobalt , nickel and etc .
the cardiovascular events ( cve ) are not distributed randomly and the pattern can be shown spatially using geographical information system ( gis ) ( 15 , 16 ) .
the city of yazd is as populated as about 430000 people ( 17 ) and is becoming an industrial pole in iran .
yazd industrial site installation is located in northwest of the city and consisted of different types of industries such as metal , chemical , electrical , textile , leather , nonmetal and pharmacy
. however , some major industries like steel industries are still working outside the specific area and due to the city s development are getting closer to city s boundaries despite the strict rules of being further . according to climatology studies the main compass rose ( windrose ) of the region is northwest to southeast ( 18 ) that possible results would be carrying the pollutants all over the city in its pathway that may cause health problems .
the current study s objectives were to find any possible spatial patterns and hotspot of cardiovascular events and to perform a correlation study to find any possible relevance between cve and location of industrial installation said above .
this ecological study was conducted in yazd , yazd province , iran during 2013 , to assess the correlation of health problems and industrial installation .
hospitals admission data was supplied by hospital information system ( his ) in three main hospitals ( afshar , shohadayekargar , and shahidsadughi ) with cardiovascular care units ( ccu ) during 2013 .
the international classification of diseases , injuries , and causes of death ( icd , 10th revision ) code i20 ( acute myocardial infarction ( ami ) ) in the his was considered .
these hospitals were taken since they are indicators of cvd admission in the city ( 19 ) and they are located in three separate locations and cover the city geographically the best .
afshar hospital admission records covered approximately 61.3% of whole admission records ( 267 of 437 records ) since it is a specialized hospital for cvds and the referenced hospital in the region .
date of admission , gender , age and patients address were included in the hospitals records .
it is nevertheless true to say that ascertaining the relevance of residence in which yazd s inhabitants are living in with cves is difficult , since they tend to move about the city and the time spent at home is not permanent .
therefore , the data is assumed the fact that a remarkable amount of people s daily life is spent at home ( e.g. at night or weekends ) .
gis is a scientific tool for health studies , spatial distribution studies and the relevance investigations ( 2022 ) .
baseline city data , including city base maps and population blocks ( based on population census of 2008 ) , was supplied with the help of yazd university geography department .
the industrial distribution map was gained from the yazd industrial installation mapping project , 2009 .
the admission data was entered to gis as points according to the addresses that were gotten ; each point represents an ami event and includes date of admission , gender and age of the patient .
gis technology was applied to create a fishnet over the city using gis data management tools_create fishnet .
fishnet cell - size ( 2km*2 km ) was obtained by testing different cell - sizes to find a minimum size with at least one event record .
attribute tables data was joined with created fishnet using gis spatial join tool . to count cvd events and
at - risk population in each fishnet cell we used a free extension for gis called 
hawth s tools is an add - on created for arcgis that provides a set of spatial analysis tools not included in the arcgis software .
it is very useful to calculate distances between points , point in polygon and polygon - to - polygon analysis ( 23 ) .
long - term exposure to air pollutants may cause cvds ( 24 , 25 ) , so the at risk population ( > 40 yr old ) was considered as the denominator of the rate fraction ( 26 , 27 ) .
event rate for each cell was calculated as below using gis field calculator function : 
 ( 1)event  rate = number  of  cvd  events  during  1  yr.at  risk  population  during  1  yr .
gis spatial statistics tools was applied to the layer containing event s rate information and the hotspot was determined in two runs .
1 ) . to figure out the possibility of significant difference in other parts of city we omitted the four spotted cluster cells and run the hotspot test again ( fig .
different industries with different levels of activity were mapped using gis union tool to unify different industries layers and to form a general distribution view of whole ( fig .
first round ami events hotspots , dark and light red color presents the cluster of ami events in yazd second round cves hotspots , dark and light red color presents the cluster of ami events in yazd spatial distribution of industries in yazd , each black point presents a single factory ; the yellow point presents the steel plants inside the city boundaries the two - tailed t- test was used to examine the differences in age , and the  test was used to compare the frequencies of both genders .
this ecological study was conducted in yazd , yazd province , iran during 2013 , to assess the correlation of health problems and industrial installation .
hospitals admission data was supplied by hospital information system ( his ) in three main hospitals ( afshar , shohadayekargar , and shahidsadughi ) with cardiovascular care units ( ccu ) during 2013 .
the international classification of diseases , injuries , and causes of death ( icd , 10th revision ) code i20 ( acute myocardial infarction ( ami ) ) in the his was considered .
these hospitals were taken since they are indicators of cvd admission in the city ( 19 ) and they are located in three separate locations and cover the city geographically the best .
afshar hospital admission records covered approximately 61.3% of whole admission records ( 267 of 437 records ) since it is a specialized hospital for cvds and the referenced hospital in the region .
date of admission , gender , age and patients address were included in the hospitals records .
it is nevertheless true to say that ascertaining the relevance of residence in which yazd s inhabitants are living in with cves is difficult , since they tend to move about the city and the time spent at home is not permanent .
therefore , the data is assumed the fact that a remarkable amount of people s daily life is spent at home ( e.g. at night or weekends ) .
gis is a scientific tool for health studies , spatial distribution studies and the relevance investigations ( 2022 ) .
baseline city data , including city base maps and population blocks ( based on population census of 2008 ) , was supplied with the help of yazd university geography department .
the industrial distribution map was gained from the yazd industrial installation mapping project , 2009 .
the admission data was entered to gis as points according to the addresses that were gotten ; each point represents an ami event and includes date of admission , gender and age of the patient .
gis technology was applied to create a fishnet over the city using gis data management tools_create fishnet .
fishnet cell - size ( 2km*2 km ) was obtained by testing different cell - sizes to find a minimum size with at least one event record .
attribute tables data was joined with created fishnet using gis spatial join tool . to count cvd events and at - risk population in each fishnet cell we used a free extension for gis called 
hawth s tools is an add - on created for arcgis that provides a set of spatial analysis tools not included in the arcgis software .
it is very useful to calculate distances between points , point in polygon and polygon - to - polygon analysis ( 23 ) .
long - term exposure to air pollutants may cause cvds ( 24 , 25 ) , so the at risk population ( > 40 yr old ) was considered as the denominator of the rate fraction ( 26 , 27 ) .
event rate for each cell was calculated as below using gis field calculator function : 
 ( 1)event  rate = number  of  cvd  events  during  1  yr.at  risk  population  during  1  yr .
gis spatial statistics tools was applied to the layer containing event s rate information and the hotspot was determined in two runs .
1 ) . to figure out the possibility of significant difference in other parts of city we omitted the four spotted cluster cells and run the hotspot test again ( fig .
different industries with different levels of activity were mapped using gis union tool to unify different industries layers and to form a general distribution view of whole ( fig .
first round ami events hotspots , dark and light red color presents the cluster of ami events in yazd second round cves hotspots , dark and light red color presents the cluster of ami events in yazd spatial distribution of industries in yazd , each black point presents a single factory ; the yellow point presents the steel plants inside the city boundaries
the two - tailed t- test was used to examine the differences in age , and the  test was used to compare the frequencies of both genders .
four hundred forty hospital admission records from three hospitals during 2013 were entered in this study . according to gender , 233 men ( 52.9% ) admission records were seen .
women seem to be older when they show myocardial infarction occurrence leading to hospital admission ( mean age 65.60 yr versus mean age 61.29 yr for men ( p < .001 ) . total mean age of myocardial infarction occurrence during 2013 in yazd was 63.26 yr . out of 440 admission records 270 admissions were recorded in afshar hospital , 91 in shohadayekargar hospital and 79 in shahidsadughi hospital ( table 1 ) . calculated rates , in each fishnet cell , for the at risk population ( > 40 yr old ) , according to equation   differ in a range of 0.00169 to 0.06153 .
myocardial infarction incidence rate was 531 per 100 000 person - year among men , 458 per 100 000 person - year among women and 783 per 100 000 person - year as total .
hospital admissions statistical summery result of running hotspot analysis showed a significant difference in four cluster cells with p value of 0.000756 , 0.000139 , 0.006469 and .033682 respectively ( fig .
thirty - one cves were in the four cluster cells and gender proportion was 17/14 ( 54.8% ) for females .
the mean age of 31 cves happened in hotspot areas was calculated as 68.05 , 61.07 and 64.9 yr for females , males and in total , respectively .
no significant difference was observed between the clustered cells and the total 437 incidents , in round one .
four more cluster cells , located in a close distance from the first four , showed significant difference from the rest ( fig .
4 ) with p of 0.0044 , 0.0298 , 0.0537 and 0.0597 respectively . mean age of 23 cves occurred in these cluster cells was calculated as 59.26 yr .
age and sex as main confounders were evaluated in the cluster areas in comparison to other areas ( cells ) .
we observed no significant difference regarding sex ( 59% in cluster cells versus 55% in total for men , p=0.47 ) and age ( 62.2114.7 in cluster cells versus 63.2813.98 in total for men , p=0.62 ) .
the frequency of ami in yazd residents has not been published prior to this study .
we found a 531 per 100,000 person - year rate among men , 458 per 100,000 person - year among women and 783 per 100,000 person - yr totally . in comparison with other population - based studies , the incidence rate of ami in residents of yazd , iran ( 783 per 100,000 population ) ,
is considerably higher than the incidence rate of initial ami observed in the san juan , puerto rico ( 163 per 100,000 population ) ( 28 ) .
the incidence rate of initial ami in finland in 1998 was 786 and 256 for men and women respectively , which is slightly higher than our results ( 29 ) .
moreover , the incidence rate in a study in denmark , 2014 showed a considerable difference in women ami rate ( 405 and 238 for men and women ) ( 30 ) .
mean age in ami events was 63.28 13.98 yr , which showed a considerable difference with a study in esfahan , iran ( mean age 73.396.10 ) ( 31 ) , and a slight difference with a study in us ( mean age 67.712.9 ) and remarkably similar to the study in puerto rico , ( 63.2 + / 13.7 for men and 68.6 + / 13.3 ) ( 28 ) .
age and sex as major confounders were controlled and no significant difference was observed in cluster cells .
industries as major point - source pollutants in urban areas are suggested to be associated with health problems ( 32 ) .
reported an association between pm concentration and industrial and urban areas of taiwan ( 33 ) and the association between pm concentration and health problems specially cardiovascular disease and hospital admission was proved by several studies ( 4 , 19 , 34 , 35 ) .
yazd with a record of about 3600 various industries can be considered as an industrial city . as shown in fig .
a study showed an association between lung cancer risk and residential proximity to industrial installations ( 21 ) .
other similar studies showed the possibility of proximity to industries and health problems ( 3639 ) .
we suggest that the observed cluster could be a result of proximity to industries cluster specifically a steel industry located inside the city borders ( fig .
3 ) . though there could be an association between road - related pollutants especially particular matters ( pm ) , nox , co , so3 and o3 and the observed sets of cluster due to the proximity exists between rather crowded highways nearby the cells . according to all ecological studies , ecological fallacy should take into consideration .this paper studied the spatial correlation of events ; the temporal correlation can not be deducted .
absence of an efficient net air pollution monitoring system in the city was a great limitation to the current study is founding to be compared with pollutants concentrations .
we suggest a follow up study in company with air pollution map database , based on air pollution monitoring system data to be done .
we also suggest a differential industries ranking system to be created according to type of industry and the amount of pollutants it makes , therefore industrial installation base - maps can be produced and new hypothesis for the association between cves and industrial installation can be developed .
we found proximity of ami events cluster to industries installations , and a steel industry , specifically .
there could be an association between road - related pollutants and the observed sets of cluster due to the proximity of rather crowded highways with the events cluster .
ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc . ) have been completely observed by the authors .
 background : the current study s objectives were to find any possible spatial patterns and hotspot of cardiovascular events and to perform a correlation study to find any possible relevance between cardiovascular disease ( cve ) and location of industrial installation said above.methods:we used the acute myocardial infarction ( ami ) hospital admission record in three main hospitals in yazd , yazd province , iran during 2013 , because of cvds and searched for possible correlation between industries as point - source pollutants and non - random distribution of ami events.results:mi incidence rate in yazd was obtained 531 per 100,000 person - year among men , 458 per 100,000 person - year among women and 783/100,000 person - yr totally . 
 we applied a gis hotspot analysis to determine feasible clusters and two sets of clusters were observed . 
 mean age of 56 ami events occurred in the cluster cells was calculated as 62.2114.75 yr . 
 age and sex as main confounders of ami were evaluated in the cluster areas in comparison to other areas . 
 we observed no significant difference regarding sex ( 59% in cluster cells versus 55% in total for men ) and age ( 62.2114.7 in cluster cells versus 63.2813.98 in total for men).conclusion : we found proximity of ami events cluster to industries installations , and a steel industry , specifically . 
 there could be an association between road - related pollutants and the observed sets of cluster due to the proximity exist between rather crowded highways nearby the events cluster . 
Introduction
Materials and Methods
Hospital admission data
Geographical information system database
Statistical Analysis
Results
Discussion
Conclusion
Ethical considerations