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unknown, or no effects outcomes) are reported by registrants as counts called aggregate 

summaries and are recorded in a separate module called Aggregate IDS. 

In Aggregate IDS, from January 1, 2007 to February 22, 2012, there were 111 reported minor 

incidents involving pendimethalin. 

For the main IDS, from January 1, 2007 to February 22, 2012, there were 24 reported incidents

involving the single chemical pendimethalin in the database. One incident was classified as 

major severity and 23 incidents were classified as moderate severity. The incident classified as 

major severity is described below in Table 1. Upon further review this incident involved more 

than one product; however, the other products were not identified. In addition, there was one 

more incident reported that involved pendimethalin and other chemicals. Overall, there are few 

incidents involving pendimethalin reported to IDS. 

Within the AHS, there are several published investigations relevant to the hazard and exposure 

characterization of pendimethalin. In 2006, Hou et al. produced a cohort evaluation of 

pendimethalin users and all cancers combined as well as specific anatomical cancer sites. Using 

pesticide exposure information collected at enrollment into the study (lifetime use of pesticides 

collected 1993-1997), and matching with state cancer registries through 2004, authors identified 

9,089 cases of cancer among pendimethalin users in the AHS, among 15,285 participants for 

which pendimethalin use information was available. Overall, authors reported no compelling 

evidence that pendimethalin use was related to all cancers combined, or with many specific 

anatomical cancer sites including prostate cancer and melanoma. Investigators did observe an 

elevated risk of rectal cancer when comparing the upper tertile of exposure with both the nonexposed and lowest exposed categories (odds ratio (OR) 4.3, 95% confidence interval (95% CI) 

1.5, 12.7), p for trend 0.007. Results were similar upon adjustment for personal protective 

equipment, i.e., intensity-weighted lifetime days. However, this result was based upon 19 cases 

of rectal cancer which is a relatively small number of exposed cases to perform a robust 

statistical analysis. Similarly, authors reported 2- to 3-fold elevated odds of lung cancer, among 

those who reported higher pendimethalin use, but trends by exposure category were inconsistent 

by use of referent group and exposure metric. Prior to this study, Alavanja et al. (2004) also 

identified a possible link between pendimethalin and lung cancer in a nested case-control study 

within the AHS. In that study, authors reported a significantly reduced risk of lung cancer when 

comparing all AHS participants with the general populations of the respective study states (IA 

and NC), but identified a 4-fold significantly increased risk of lung cancer among pendimethalin 

users (OR 4.4 (95% CI 1.2, 15.4), p for trend 0.003). While authors were able to control for the 

effect of smoking when estimating the association between pendimethalin and lung cancer, 

authors note all cases of lung cancer identified in the AHS are among current and former 

smokers. Therefore, authors could not rule out a role of residual confounding by smoking in 

estimating the association. However, it is notable that this potential link with lung cancer has 

now been observed in two studies within the AHS, at two points in time, using similar data to 

measure exposure and co-variables including smoking. Within this cohort, authors also reported 

a significant association between pendimethalin users and pancreatic cancer (OR 3.0 (95% CI 

1.3, 7.2), p=0.01) comparing the upper tertile with the no-exposed group. However, authors note 

there was no a priori hypothesis for this association, and many statistical tests were performed 

and not adjusted in final analyses.
Page 4 of 5

In a related AHS study of self-reported myocardial infarction (MI) or heart attack, authors 

observed an association between pendamethalin users and MI (OR 2.5 (95% CI 1.2, 4.9). 

However this finding was based upon 9 pendamethalin exposed cases of MI. Authors found no 

association among users of any of the 50 pesticides included in the AHS, but they did report 

associations with 6 of 27 pesticides evaluated, including pendamethalin. Given the small number 

of pendimethalin exposed cases of MI, the correlated nature of many pesticides used by cohort 

members which is difficult to disentangle in statistical analyses only, and the lack of an a priori 

hypothesis and no known or hypothesized mechanism of action, these results should be 

interpreted with caution.

Based on the generally low frequency and severity of incident cases reported for pendimethalin, 

there does not appear to be a concern at this time that would warrant further investigation. The 

Agency will continue to monitor the incident information and if a concern is triggered, additional 

analysis will be included in the risk assessment and follow-up studies from the AHS will be 

evaluated if available at the time of the risk assessment.

.

Table 1: Main IDS high severity incidents involving pendimethalin

Chemical: Pendimethalin PC code: 

027401

Human 

Incidents

Incident 

Number

Incident 

Date

Product 

Name

Registration 

Number City State

Exposure 

Type*

Incident Description

022923 -

00004 5/25/2011

PROWL H2O 

HERBICIDE 000241-00418 WINDBER PA HB

Unknown age adult male applied 

product along with other products 

(not reported). He experienced pain 

and heaviness in his chest. He was 

hospitalized with unspecified tests 

and treatment.

* Severity Categories

na – not available

H-A Human Fatality Death (if the person died)

H-B Human Major Major (if the person alleged or exhibited symptoms which may have been life-threatening, or resulted in adverse 

reproductive effects or in residual disability)

H-C Human Moderate Moderate (if the person alleged or exhibited symptoms more pronounced, more prolonged or of a more systemic 

nature than minor symptoms; and involved some form of treatment, even though symptoms were not life 

threatening and the person returned to his/her pre-exposure state of health with no additional residual disability)

H-D Human Minor Minor (if the person alleged or exhibited some symptoms, but they were minimally traumatic; the symptoms 

resolved rapidly and usually involve skin, eye or respiratory irritation)

H-E Human Unspecified Unspecified (if symptoms are unknown, unspecified or are alleged to be of a delayed or chronic nature that may 

appear in the future)

H Human Undetermined (an undetermined severity)

from 40 CFR § 159.184

Materials Referenced

Alavanja MC, Dosemeci M, Samanic C, Lubin J, Lynch CF, Knott C, Barker J,

Hoppin JA, Sandler DP, Coble J, Thomas K, Blair A. Pesticides and lung cancer

risk in the agricultural health study cohort. Am J Epidemiol. 2004 Nov

1;160(9):876-85. PubMed PMID: 15496540.

Andreotti G, Freeman LE, Hou L, Coble J, Rusiecki J, Hoppin JA, Silverman DT, 
Page 5 of 5

Alavanja MC. Agricultural pesticide use and pancreatic cancer risk in the

Agricultural Health Study Cohort. Int J Cancer. 2009 May 15;124(10):2495-500.

PubMed PMID: 19142867; PubMed Central PMCID: PMC2674312.

Dayton SB, Sandler DP, Blair A, Alavanja M, Beane Freeman LE, Hoppin JA.

Pesticide use and myocardial infarction incidence among farm women in the

agricultural health study. J Occup Environ Med. 2010 Jul;52(7):693-7. PubMed

PMID: 20595914; PubMed Central PMCID: PMC2927225.

Hou L, Lee WJ, Rusiecki J, Hoppin JA, Blair A, Bonner MR, Lubin JH, Samanic C,

Sandler DP, Dosemeci M, Alavanja MC. Pendimethalin exposure and cancer incidence 

among pesticide applicators. Epidemiology. 2006 May;17(3):302-7. PubMed PMID:

16452832; PubMed Central PMCID: PMC1513643.