Research reveals exactly how coughing is triggered by environmental irritants

Chemicals often Reason for Coughing


Scientists have revealed how environmental irritants such as air pollution and cigarette smoke cause people to cough, in research published today in the American Journal of Respiratory and Critical Care Medicine. The authors of the study, from Imperial College London and the University of Hull, have identified the reaction inside the lungs that can trigger coughing when a person is exposed to particular irritants in the air. They suggest that their findings may ultimately lead to the development of new treatments for chronic coughing. 

Coughing is the most common reason for people visiting a family doctor. Treatment options are limited for people with chronic coughing; a recent study concluded that over-the-counter remedies are ineffective and there is increasing concern about the safety of these therapies in children. 

Today’s study indicates, for the first time, how coughing can be triggered when a person is exposed to certain irritants in the air. It shows that the irritants can switch on receptor proteins called TRPA1 on the surface of nerve endings in the lungs. This switches on sensory nerves, which then trigger a cough reflex. The researchers say coughing could potentially be treated by blocking TRPA1 receptors, to stop irritants in the air from setting off this chain reaction. They hope that this could ultimately help millions of people whose lives are affected by chronic coughing. 

Professor Maria Belvisi, corresponding author of the study from the National Heart and Lung Institute at Imperial College London, said: “For some people, chronic coughing can be annoying and uncomfortable, but for others it can be distressing and can have a severe impact on their quality of life. Many people say that certain things in the air can make them cough and we are very excited that we have shown, for the first time, exactly what is probably happening inside the lungs. Now that we think we have cracked the mechanism, we can start investigating whether we can stop people from coughing excessively by blocking the receptor protein that triggers it.” 

To reach their conclusions, the researchers first looked at sensory nerves from mice, guinea pigs and humans, and showed that the receptors on the sensory nerves were activated by a number of irritants, including a key compound in cigarette smoke (acrolein) and a chemical called cinnamaldehyde. The researchers then blocked the receptors and showed that these substances no longer activated the nerves. 

To establish whether activating the receptor causes coughing, the researchers looked at the effect of acrolein on guinea pigs, as they have a coughing reflex. The researchers assessed the guinea pigs’ coughing after inhaling acrolein. The compound caused coughing, and the higher the concentration, the more the guinea pigs coughed. The researchers then showed that blocking the receptor using a drug significantly reduced the guinea pigs’ coughing response to the compound.

Finally, researchers led by Professor Alyn Morice at the University of Hull looked at the effect of inhaling the chemical cinnamaldehyde in humans. Ten healthy, non-smoking volunteers inhaled the chemical, as well as control substances. The researchers measured their cough response on five occasions, 2-3 days apart. All of the volunteers coughed after inhaling the compound. 

Reference: Imperial College London, Research reveals exactly how coughing is triggered by environmental irritants, November 23, 2009

Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity

Air Pollution in Mexico City

Surprisingly little is known about the effects of big-city air pollution on olfactory function and even less about its effects on the intranasal trigeminal system, which elicits sensations like burning, stinging, pungent, or fresh and contributes to the overall chemosensory experience. 

Using the Sniffin’ Sticks olfactory test battery and an established test for intranasal trigeminal perception, we compared the olfactory performance and trigeminal sensitivity of residents of Mexico City, a region with high air pollution, with the performance of a control population from the Mexican state of Tlaxcala, a geographically comparable but less polluted region. 

We compared the ability of 30 young adults from each location to detect a rose-like odor (2-phenyl ethanol), to discriminate between different odorants, and to identify several other common odorants. The control subjects from Tlaxcala detected 2-phenyl ethanol at significantly lower concentrations than the Mexico City subjects, they could discriminate between odorants significantly better, and they performed significantly better in the test of trigeminal sensitivity. 

We conclude that Mexico City air pollution impairs olfactory function and intranasal trigeminal sensitivity, even in otherwise healthy young adults. 

Reference:    Guarneros M, Hummel T, Martínez-Gómez M, Hudson R., Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity, Chem Senses. 2009 Oct 9.

Harvard: Lead in bone associated with increased risk of death from cardiovascular disease in men

Patient with heart disease from lead


Growing evidence shows that exposure to lead in the environment is associated with cardiovascular disease, including increased risk of hypertension. However, those studies have looked at lead concentrations in blood, not bone lead, a better indicator of cumulative lead exposure over time. In a new study, researchers at the Harvard School of Public Health (HSPH) and the University of Michigan School of Public Health found that bone lead was associated with a higher risk of death from all causes, particularly from cardiovascular disease. It is the first study to analyze the association between bone lead and mortality.


The study appears online on September 8, 2009, on the website of the journal Circulation and will appear in a later print edition. 

“The findings with bone lead are dramatic. It is the first time we have had a biomarker of cumulative exposure to lead and the strong findings suggest that, even in an era when current exposures are low, past exposures to lead represent an important predictor of cardiovascular death, with important public health implications worldwide,” said Marc Weisskopf, assistant professor of environmental and occupational epidemiology at HSPH and lead author of the study.

Air pollution was the main source of lead in the environment in recent years, though it has been decreasing since leaded gasoline was banned in the U.S. in the mid-1990s. Most of the lead circulating in the body is deposited in bone and remains there for years, unlike blood lead, which has a half life of about 30 days. Since adverse effects from lead on the cardiovascular system would be expected to show up over time, the researchers expected that bone lead would be a better marker of chronic toxicity.


The researchers, led by Weisskopf and senior author Howard Hu, professor of environmental health, epidemiology and internal medicine at the University of Michigan School of Public Health, analyzed data from 868 participants in the Department of Veterans Affairs Normative Aging Study, a study of aging in men that began in 1963. Blood lead and bone lead—analyzed using X-ray fluorescence—were measured for each of the participants. The results showed that the risk of death from cardiovascular disease was almost six times higher in men with the highest levels of bone lead compared to men with the lowest levels. The risk of death from all causes was 2.5 times higher in men with the highest levels of lead compared to those with the lowest levels. The results appeared independent of age, smoking, education, race, alcohol, physical activity, BMI, high density lipoprotein or total cholesterol levels, hypertension or diabetes.


There are a number of mechanisms, such as increased oxidative stress, by which lead exposure may result in cardiovascular mortality, say the authors. They also note that, in addition to high blood pressure, exposure to lead has been associated with widened pulse-pressure (an indicator of arterial stiffening) and heart disease.


Given that bone lead may be a better biomarker of cumulative lead exposure than blood lead, it may be the best predictor of chronic disease from exposure to lead in the environment. “In addition to spurring further public health measures to reduce exposure to lead and to begin monitoring for cumulative exposure, mechanistic and clinical research is needed to determine if opportunities exist to conduct targeted screening and treatment that can further reduce the burden of cardiovascular disease for the millions of adults who have had years of elevated lead exposure in the past,” said Hu.


Reference:    Harvard School of Public Health, Lead in bone associated with increased risk of death from cardiovascular disease in men, Boston, MA, September 9, 2009

Life prevalence of upper respiratory tract diseases and asthma among children residing in rural area near a regional industrial park

Industrial Areas often ruin the Health of ChildrenThe 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 

Childhood Asthma – Study shows how neighborhood characteristics play a significant role

Air Pollution causes Asthma

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