Air pollution as a potential contributor of disease

There has been remarkable progress over the past 20years in pushing forward our understanding of many facets of autoimmune disease. Indeed, knowledge of the genetic basis of autoimmunity and the molecular and cellular pathways involved in its pathogenesis has reached an unprecedented level. Yet this knowledge has not served to prevent autoimmune disease nor to curtail the dramatic rise in its incidence over the same interval. Population-level genetic changes cannot explain this trend; thus, environmental factors are strongly implicated. Among the possible environmental contributors to autoimmune disease, air pollution exposure has received very little attention. Although there is only a small amount of published data directly examining a possible causal relationship between air pollution exposure and autoimmunity, data from related fields suggests that it could facilitate autoimmunity as well. If correct, this hypothesis could prove to have sizeable public health implications. 

Reference:   Ritz SA, Air pollution as a potential contributor to the ‘epidemic’ of autoimmune disease, Medical Sciences Division, Northern Ontario School of Medicine, East Campus – Laurentian University, Med Hypotheses. 2009 Aug 7.

The study described was initiated by the Israel Ministry of Health as an effort to respond to and deal with public concern about possible health disorders related to odorous emissions (composed of a great many of organic and inorganic chemicals) from the regional industrial park (IP) in the Negev, southern Israel. Previous ecological studies found that adverse health effects in the Negev Bedouin population were associated with residential proximity to the IP. The objective of the current study was to investigate a hypothesis concerning the link between the IP proximity and life prevalence (LP) of upper respiratory tract chronic diseases (URTCD) and asthma in children aged 0-14 years living in rural Negev, Israel, in small agricultural communities.  

The cross-sectional study was conducted in 7 localities simultaneously during 2002. The following indirect exposure indicators were used: (1) distance (less than 20 km/ more than 20 km) from the IP (‘distance’); (2) presence (yes/no) of the dominant wind direction being from the IP toward a child’s locality (‘wind direction’); and (3) the child’s mother having made odour complaints (yes/no) related to the IP (‘odour complaints’). A 20 km cut-off point was used for ‘distance’ dichotomization as derived from the maximum range of ‘odour complaints’. This gave 3 proximal and 4 distant localities, and division of these by the ‘wind direction’ gave one versus two localities. The study population consisted of 550 children born in the localities. Medical diagnoses were collected from local clinic records. The following were included in the interviewer-administered questionnaire for a child’s parents: (1) demography (the child’s birth date, gender, mother being married or not, parental origin and education, number of siblings); (2) the child’s birth history (pregnancy and delivery) and breast-feeding duration; (3) the child’s parental respiratory health; and (4) environmental factors (parental smoking and occupational hazardous exposure, domestic use of pesticides, domestic animals, outdoor odour related to the IP emissions). For statistical analysis, Pearson’s chi(2), t-tests and multivariate logistic regressions were used, as well as adjusted odds ratios (OR) within a 95% confidence interval.  

The multivariate analysis showed that increased LP of URTCD in children of proximal localities was statistically significant when associated with odour complaints (OR = 3.76 [1.16, 12.23]). In proximal localities, LP of URTCD was higher (at borderline level statistical insignificance p = 0.06) than in distant localities (OR = 2.31 [0.96, 5.55]). The following factors were found to be related to the excess of the LP of URTCD: (1) father’s lower education (by distance: OR = 2.62 [1.23, 5.57]; by wind direction: OR = 4.07 [1.65, 10.03]); (2) in-vitro fertilization (by distance: OR = 3.03 [1.17, 7.87]; by wind direction: OR = 4.34 [1.48, 12.72]). In proximal localities, the increase in asthma LP was associated with: (1) wind direction (OR = 1.95 [1.01, 3.76]); (2) a child’s male gender (OR = 2.95 [1.48, 5.87]); and (3) a child’s mother’s having had an acute infectious disease during pregnancy (OR = 4.84 [1.33, 17.63]).  

An increased LP of chronic respiratory morbidity among children living in small agricultural localities in the Negev was found to be associated with indirect measurements of exposure (distance, wind direction and odour complaints) to IP emissions. These results, in conjunction with previously reported findings in the Negev Bedouin population, indicate a need for environmental protection measures, and monitoring of air pollution and the health of the rural population. 

Reference: Karakis I, Kordysh E, Lahav T, Bolotin A, Glazer Y, Vardi H, Belmaker I, Sarov B., Life prevalence of upper respiratory tract diseases and asthma among children residing in rural area near a regional industrial park: cross-sectional study, School of Public Health, University of Haifa, Haifa, Israel. Rural Remote Health. 2009 Jul-Sep;9(3):1092 

Researchers for the first time have linked air pollution exposure before birth with lower IQ scores in childhood, bolstering evidence that smog may harm the developing brain. 

The results are in a study of 249 children of New York City women who wore backpack air monitors for 48 hours during the last few months of pregnancy. They lived in mostly low-income neighborhoods in northern Manhattan and the South Bronx. They had varying levels of exposure to typical kinds of urban air pollution, mostly from car, bus and truck exhaust. 

At age 5, before starting school, the children were given IQ tests. Those exposed to the most pollution before birth scored on average four to five points lower than children with less exposure. 

That’s a big enough difference that it could affect children’s performance in school, said Frederica Perera, the study’s lead author and director of the Columbia Center for Children’s Environmental Health.      

Dr. Michael Msall, a University of Chicago pediatrician not involved in the research, said the study doesn’t mean that children living in congested cities “aren’t going to learn to read and write and spell.” 

But it does suggest that you don’t have to live right next door to a belching factory to face pollution health risks, and that there may be more dangers from typical urban air pollution than previously thought, he said. 

“We are learning more and more about low-dose exposure and how things we take for granted may not be a free ride,” he said.

While future research is needed to confirm the new results, the findings suggest exposure to air pollution before birth could have the same harmful effects on the developing brain as exposure to lead, said Patrick Breysse, an environmental health specialist at Johns Hopkins’ school of public health. 

And along with other environmental harms and disadvantages low-income children are exposed to, it could help explain why they often do worse academically than children from wealthier families, Breysse said.  

“It’s a profound observation,” he said. “This paper is going to open a lot of eyes.”

The study in the August edition of Pediatrics was released Monday. 

In earlier research, involving some of the same children and others, Perera linked prenatal exposure to air pollution with genetic abnormalities at birth that could increase risks for cancer; smaller newborn head size and reduced birth weight. Her research team also has linked it with developmental delays at age 3 and with children’s asthma. 

The researchers studied pollutants that can cross the placenta and are known scientifically as polycyclic aromatic hydrocarbons. Main sources include vehicle exhaust and factory emissions. Tobacco smoke is another source, but mothers in the study were nonsmokers. 

A total of 140 study children, 56 percent, were in the high exposure group. That means their mothers likely lived close to heavily congested streets, bus depots and other typical sources of city air pollution; the researchers are still examining data to confirm that, Perera said. The mothers were black or Dominican-American; the results likely apply to other groups, researchers said. 

The researchers took into account other factors that could influence IQ, including secondhand smoke exposure, the home learning environment and air pollution exposure after birth, and still found a strong influence from prenatal exposure, Perera said. 

Dr. Robert Geller, an Emory University pediatrician and toxicologist, said the study can’t completely rule out that pollution exposure during early childhood might have contributed. He also noted fewer mothers in the high exposure group had graduated from high school. While that might also have contributed to the high-dose children’s lower IQ scores, the study still provides compelling evidence implicating prenatal pollution exposure that should prompt additional studies, Geller said. 

The researchers said they plan to continuing monitoring and testing the children to learn whether school performance is affected and if there are any additional long-term effects. 

Reference:    Columbia Center for Children’s Environmental Health, Kids’ lower IQ scores linked to prenatal pollution, July 20, 2009 

Neighborhoods with restaurants, entertainment, cultural facilities and ethnic diversity have lower asthma rates in the city of Chicago than neighbourhoods where residents are less likely to move, and where there are more churches and not-for-profit facilities. 

Published in the spring 2009 issue of  The Journal of Allergy and Clinical Immunology, the two-year study led by Ruchi Gupta, MD, MPH, a researcher at Children’s Memorial Hospital and associate professor of pediatrics at Northwestern University’s Feinberg School of Medicine, showed that neighborhoods with more community vitality, specifically economic potential, community amenities and social capital had lower asthma rates. The study focused on 287 Chicago neighborhoods, where nearly 50,000 children grades K-8 were screened for asthma. Asthma is the leading chronic childhood illness, affecting more than 9 million children nationwide. Chicago has twice the national average asthma mortality rate. 

 â€œPrevious studies showed that neighborhoods right next to each other with similar racial makeup had very different asthma rates; we wanted to see what else was going on in each neighborhood to cause such a disparity,” said Gupta. “So we looked at specific factors in each neighborhood.” 

Ethnically diverse communities with greater potential for economic development that were civically engaged, meaning that there were high percentages of registered voters had low asthma rates while stable communities, defined as communities where residents were less likely to move, with more social interaction had higher asthma rates. Although it is not entirely clear how these factors affect health outcomes, previous research has shown that asthma and other chronic illnesses of childhood are associated with poverty, which may explain why communities with low asthma rates had a greater capacity for economic growth. 

Researchers suspect that the association between neighborhood stability and asthma may indicate that homes in which residents are less likely to move receive less frequent and thorough cleanings, leading to an accumulation of indoor pollutants known to trigger asthma.  Similarly, the association of higher interaction potential and increased asthma may signify overcrowding, which also leads to increased indoor pollutants.

Besides community influence, other factors that affect the rate of childhood asthma include income and education, housing problems with sensitivities to cockroaches, dust mites, mice and rats, exposure to air pollution and individual factors. A collaboration of many factors may ultimately cause asthma.

With these insights, we are better equipped to develop more effective interventions to help reduce asthma in children living in urban environments,” said Gupta. 

Information on the neighborhoods was gathered from the Metro Chicago Information Center. Gupta collaborated on this study with Xingyou Zhang, PhD, Lisa K Sharp, PhD, John J Shannon, MD, and Kevin B Weiss, MD, MPH. In a currently ongoing study, Gupta is further investigating the true importance of these protective factors by talking to and surveying residents in a Chicago neighborhood with a high childhood asthma rate. 

Reference: Childrens Memorial Hospital, Pree Release: Study shows how neighborhood characteristics play a significant role in childhood asthma, June 5, 2009