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Prolonged exposure to some agricultural pesticides may increase the risk of lung cancer in agricultural workers
ARTICLE IN PRESS Evidence-Based Healthcare & Public Health (2005) 9, 203–205
www.elsevier.com/locate/ebhph
COMMENTARY
Prolonged exposure to some agricultural pesticides may increase the risk of lung cancer in agricultural workers$ Barbara Dinham (Commentator) Director, Pesticide Action Network UK
KEYWORDS Herbicide; Insecticide; Lung cancer; Pesticides; Cohort study
Question: Does exposure to agricultural pesticides increase the risk of lung cancer? Study design: Cohort study Main results: Four of the most commonly used agricultural pesticides (diazinon, dieldrin, metalochlor and pendimethalin) significantly increased the risk of lung cancer in people with the greatest exposure, compared with people who had no exposure (see results table). Three other commonly used pesticides (carbofuran, chlorpyrifos, and dicamba) also increased the risk of lung cancer, but the results were not statistically significant (see results table).There were insufficient numbers of spouses with lung cancer who were directly exposed to specific pesticides to calculate any associated risk. Authors’ conclusions: Prolonged exposure to the most commonly used agricultural pesticides increased the risk of lung cancer in farmers and commercial pesticide users. However, this increased risk was only significant for prolonged exposure to diazinon, dieldrin, metalochlor and pendimethalin. It is important to note that the participants in this study were exposed to higher levels for longer periods than the general population, due to their professional, agricultural use of insecticides and herbicides. & 2005 Elsevier Ltd. All rights reserved.
Further details Setting Iowa and North Carolina, USA; enrolment from 1993–1997; follow-up from enrolment to December 2001.
$ Abstracted from: Alavanja MCR, Dosemeci M, Samanic C et al. Pesticides and lung cancer risk in the agricultural health study cohort. American Journal of Epidemiology 2004; 160: 876–885.
1744-2249/$ - see front matter & 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ehbc.2005.03.029
ARTICLE IN PRESS 204
EVIDENCE-BASED PUBLIC HEALTH
Results table Lung cancer risk (for highest exposure v no exposure groups) associated with the seven most commonly used herbicides/insecticides Herbicide/Insecticide
Exposure time (lifetime days)
Lifetime exposure OR (95% CI)y
Carbofuran Chlorpyrifos Diazinon Dicamba Dieldrin Metalochlor Pendimethalin
4108.5 4116 o108.5 4224.7 450.7 4457 4224.7
1.6 1.7 2.7 1.6 5.3 4.1 3.5
y
(0.9 (0.9 (1.2 (0.7 (1.5 (1.6 (1.1
to to to to to to to
3.2) 3.3) 6.1) 3.4) 18.6) 10.4) 10.5)
OR adjusted for smoking, age, gender, and total days of any pesticide exposure
Participants 57,284 pesticide users (both private and commercial) and 32,333 controls (the spouses of private farmers) with no previous history of lung cancer, participating in the Agricultural Health Study.
Analysis A questionnaire (one for pesticide users, another for their spouses) was completed by all participants at enrolment. The questions asked about use of 50 different pesticides (ever/never), duration of exposure (years) and frequency of use (days per year), pesticide application methods, protective equipment used, lung cancer history, other medical conditions and life-style information such as smoking, diet, physical activity, age, height and weight. Two measures of exposure were calculated based on this information: lifetime exposure days (application days per year x total years of exposure) and intensity-weighted days (application-days per year x total years of exposure x exposure intensity index). Odds ratios were adjusted for age, gender, smoking history, and total pesticide exposure days of any pesticide. A standardised lung cancer incidence ratio of 0.44, 95% CI 0.39 to 0.49 was calculated for the population of Iowa and North Carolina and used to predict the number of expected cases of lung cancer. Actual cancer incidence data were obtained from population based cancer registries.
Main outcomes Incidence of lung cancer.
Notes Direct measurements of pesticide exposure were not made. Rather, exposure estimates were based on a review of the questionnaire data. Participants were asked to recall pesticide use from previous years; recall bias may have influenced the exposure data. The follow-up time is relatively short; a longer follow-up time is needed to assess the influence of longer term exposures on the incidence of lung cancer. Fifty different pesticides were analysed, increasing the possibility that some of the findings may be due to chance. Sources of funding: Abstract provided by Bazian Ltd
ARTICLE IN PRESS EVIDENCE-BASED PUBLIC HEALTH
205
Commentary Pesticides are toxic chemicals that can have acute or chronic effects on the health of those who are exposed to them, particularly in countries where precautionary measures such as protective clothing, are not common place. Before registering a pesticide and allowing its release onto the market, rigorous safety testing is required. Chronic effects associated with pesticide use, however, are usually only identified through epidemiological studies. Rural communities have expressed a concern that long term exposure to pesticides during application or through spray drift may be related to cancer, but the time lag between exposure and disease makes it difficult to establish a link. Alavanja and colleagues’ study is particularly valuable because of its focus on commonly used pesticides and its examination of a specific health outcome. Several studies of pesticide exposure in rural areas do not identify specific adverse health effects and, possibly due to a focus on tobacco, may have over-looked the relationship between pesticide use and lung cancer. Epidemiological studies on the chronic health effects of pesticides have focused on exposure to the highly persistent organochlorine pesticides that build up in the fatty tissue of the body. Although these studies are valuable, most of these pesticides, with the exception of DDT, were banned in the 1980s and are no longer in use. Also, the majority of studies of agricultural work-related pesticide exposure are in men. Distinguishing health outcomes in men and women is important
because of their physiological, sociological and economic differences. Alavanja and colleagues’ study has several strengths: most of the pesticides are currently in use; the study focuses on a specific health outcome; the analysis controlled for other risk factors for lung cancer in the cohort, such as smoking; and the study differentiates between the person working directly with the pesticide and their spouse. The study was large scale and provides robust evidence that the risk of lung cancer is linked to exposure to certain pesticides. Although diseases related to agrochemical use, such as various forms of cancer, can be attributed to other risk factors (for example smoking or history of the disease in a family), the associations suggested in this study are sufficient for policy makers in both health and agriculture to take action to protect users from exposure to these pesticides. Doctors too should be alerted by this evidence to check work history for pesticide exposure when exploring possible causes of lung cancer, and for reporting such information. Generally only the acute effects of pesticide exposure are documented, and this study should encourage policy makers to establish a system for documenting their chronic effects on health. Pesticide regulatory authorities should, as a minimum precautionary measure, require warning labels on high-risk pesticides, and possibly even withdraw very high risk products from the market.
www.elsevier.com/locate/ebhph
COMMENTARY
Prolonged exposure to some agricultural pesticides may increase the risk of lung cancer in agricultural workers$ Barbara Dinham (Commentator) Director, Pesticide Action Network UK
KEYWORDS Herbicide; Insecticide; Lung cancer; Pesticides; Cohort study
Question: Does exposure to agricultural pesticides increase the risk of lung cancer? Study design: Cohort study Main results: Four of the most commonly used agricultural pesticides (diazinon, dieldrin, metalochlor and pendimethalin) significantly increased the risk of lung cancer in people with the greatest exposure, compared with people who had no exposure (see results table). Three other commonly used pesticides (carbofuran, chlorpyrifos, and dicamba) also increased the risk of lung cancer, but the results were not statistically significant (see results table).There were insufficient numbers of spouses with lung cancer who were directly exposed to specific pesticides to calculate any associated risk. Authors’ conclusions: Prolonged exposure to the most commonly used agricultural pesticides increased the risk of lung cancer in farmers and commercial pesticide users. However, this increased risk was only significant for prolonged exposure to diazinon, dieldrin, metalochlor and pendimethalin. It is important to note that the participants in this study were exposed to higher levels for longer periods than the general population, due to their professional, agricultural use of insecticides and herbicides. & 2005 Elsevier Ltd. All rights reserved.
Further details Setting Iowa and North Carolina, USA; enrolment from 1993–1997; follow-up from enrolment to December 2001.
$ Abstracted from: Alavanja MCR, Dosemeci M, Samanic C et al. Pesticides and lung cancer risk in the agricultural health study cohort. American Journal of Epidemiology 2004; 160: 876–885.
1744-2249/$ - see front matter & 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ehbc.2005.03.029
ARTICLE IN PRESS 204
EVIDENCE-BASED PUBLIC HEALTH
Results table Lung cancer risk (for highest exposure v no exposure groups) associated with the seven most commonly used herbicides/insecticides Herbicide/Insecticide
Exposure time (lifetime days)
Lifetime exposure OR (95% CI)y
Carbofuran Chlorpyrifos Diazinon Dicamba Dieldrin Metalochlor Pendimethalin
4108.5 4116 o108.5 4224.7 450.7 4457 4224.7
1.6 1.7 2.7 1.6 5.3 4.1 3.5
y
(0.9 (0.9 (1.2 (0.7 (1.5 (1.6 (1.1
to to to to to to to
3.2) 3.3) 6.1) 3.4) 18.6) 10.4) 10.5)
OR adjusted for smoking, age, gender, and total days of any pesticide exposure
Participants 57,284 pesticide users (both private and commercial) and 32,333 controls (the spouses of private farmers) with no previous history of lung cancer, participating in the Agricultural Health Study.
Analysis A questionnaire (one for pesticide users, another for their spouses) was completed by all participants at enrolment. The questions asked about use of 50 different pesticides (ever/never), duration of exposure (years) and frequency of use (days per year), pesticide application methods, protective equipment used, lung cancer history, other medical conditions and life-style information such as smoking, diet, physical activity, age, height and weight. Two measures of exposure were calculated based on this information: lifetime exposure days (application days per year x total years of exposure) and intensity-weighted days (application-days per year x total years of exposure x exposure intensity index). Odds ratios were adjusted for age, gender, smoking history, and total pesticide exposure days of any pesticide. A standardised lung cancer incidence ratio of 0.44, 95% CI 0.39 to 0.49 was calculated for the population of Iowa and North Carolina and used to predict the number of expected cases of lung cancer. Actual cancer incidence data were obtained from population based cancer registries.
Main outcomes Incidence of lung cancer.
Notes Direct measurements of pesticide exposure were not made. Rather, exposure estimates were based on a review of the questionnaire data. Participants were asked to recall pesticide use from previous years; recall bias may have influenced the exposure data. The follow-up time is relatively short; a longer follow-up time is needed to assess the influence of longer term exposures on the incidence of lung cancer. Fifty different pesticides were analysed, increasing the possibility that some of the findings may be due to chance. Sources of funding: Abstract provided by Bazian Ltd
ARTICLE IN PRESS EVIDENCE-BASED PUBLIC HEALTH
205
Commentary Pesticides are toxic chemicals that can have acute or chronic effects on the health of those who are exposed to them, particularly in countries where precautionary measures such as protective clothing, are not common place. Before registering a pesticide and allowing its release onto the market, rigorous safety testing is required. Chronic effects associated with pesticide use, however, are usually only identified through epidemiological studies. Rural communities have expressed a concern that long term exposure to pesticides during application or through spray drift may be related to cancer, but the time lag between exposure and disease makes it difficult to establish a link. Alavanja and colleagues’ study is particularly valuable because of its focus on commonly used pesticides and its examination of a specific health outcome. Several studies of pesticide exposure in rural areas do not identify specific adverse health effects and, possibly due to a focus on tobacco, may have over-looked the relationship between pesticide use and lung cancer. Epidemiological studies on the chronic health effects of pesticides have focused on exposure to the highly persistent organochlorine pesticides that build up in the fatty tissue of the body. Although these studies are valuable, most of these pesticides, with the exception of DDT, were banned in the 1980s and are no longer in use. Also, the majority of studies of agricultural work-related pesticide exposure are in men. Distinguishing health outcomes in men and women is important
because of their physiological, sociological and economic differences. Alavanja and colleagues’ study has several strengths: most of the pesticides are currently in use; the study focuses on a specific health outcome; the analysis controlled for other risk factors for lung cancer in the cohort, such as smoking; and the study differentiates between the person working directly with the pesticide and their spouse. The study was large scale and provides robust evidence that the risk of lung cancer is linked to exposure to certain pesticides. Although diseases related to agrochemical use, such as various forms of cancer, can be attributed to other risk factors (for example smoking or history of the disease in a family), the associations suggested in this study are sufficient for policy makers in both health and agriculture to take action to protect users from exposure to these pesticides. Doctors too should be alerted by this evidence to check work history for pesticide exposure when exploring possible causes of lung cancer, and for reporting such information. Generally only the acute effects of pesticide exposure are documented, and this study should encourage policy makers to establish a system for documenting their chronic effects on health. Pesticide regulatory authorities should, as a minimum precautionary measure, require warning labels on high-risk pesticides, and possibly even withdraw very high risk products from the market.