12.
Occupational Exposure to Toxic Materials and Pesticides
Authors
The information in this chapter was prepared by the following individuals:
Description of occupational exposure to toxic materials:
o Tim Flood, M.D., Medical Director, Chronic Disease Epidemiology, Arizona Department of Health
o Michelle Novoa
Description of farm worker exposure to pesticides:
o Tim Flood, M.D., Medical Director, Chronic Disease Epidemiology, Arizona Department of Health
Occupational Exposure to Toxic Materials
Scope
If not properly controlled, workplace exposures may occur at levels tens or hundreds of times higher in the workplace than in the general environment. Because large numbers of people are exposed to toxic materials in their workplace, the Committee was concerned with workplace exposures. This section of the report addresses potential work-related cancer and non-cancer health effects.
Data Source
Non-Malignant Occupational Illnesses
Estimates of the number of non-malignant illnesses occurring each year in Arizona are derived from worker's compensation claims data, and the annual survey of Arizona occupational illnesses and injuries conducted by the Industrial Commission of Arizona (ICA).
Neither of these data bases includes all occupational illness because:
o Occupational disease is often unrecognized, especially since it often occurs after a person retires.
o An employee may have worked for several establishments and been exposed to multiple agents.
o Reporting is notoriously incomplete even for recognized occupational illnesses.
The ICA conducts an annual survey of Arizona workplaces as part of a federal Occupational Safety and Health Administration (OSHA) survey of occupational illness nationwide.
o Employers are required by law to maintain a record of all work-related illnesses and injuries in a log, named Form 200, and to disclose this information to the ICA in the annual survey.
In 1991, the latest year for which data is available, the ICA surveyed 6,700 Arizona employers who were selected by Standard Industrial Classification code and number of workers. The sample is designed to be representative of all Arizona employers.
Occupational illnesses eligible for reporting to this system include:
--------------------------------------------------------------- | ... any abnormal condition or disorder, other than one | | resulting from occupational injury, caused by exposure to | | factors associated with employment. | ---------------------------------------------------------------
In order to be recorded on OSHA Form 200 the illness must:
----------------------------------------------------------- | ...result in loss of consciousness, restricted work | | activity, transfer to another job, or require medical | | treatment beyond first aid. | -----------------------------------------------------------
The system therefore tends to list only illnesses which are relatively easy to diagnose, relate to the workplace, and are serious enough to be recordable. Illnesses recognized after a person leaves employment would not be recorded.
Despite these short-comings, the Committee has used the ICA data for this report because there are no other reasonable data sources to use, nor are there other sources that describe the number of illnesses of workers.
Cancer Related to Occupation
The Committee explored various options in search of Arizona specific data. Many agencies, for example, were contacted to access information relating to illness and cancers for specific chemicals, including the ICA, State Workers Compensation, ADOSH, and ADEQ. No agency, however, could supply the information in this type of detail.
Similarly, the Committee tried to correlate high risk industries, chemicals and processes with the number of Arizona employees in those industries. With that data, it tried to estimate the number of cancer cases that would occur among Arizona workers. This method also proved to be unacceptable, however, because the Committee could not document the number of exposed workers.
The Committee, therefore, decided to use estimates obtained from a 1981 report by Doll and Peto. Their widely respected study of attributable risk concluded that approximately 4% of all cancer deaths in the U.S. are related to exposures to chemicals on the job.
One author (Bridbord et al., 1978) estimates this number to be around 25%. Other authors estimate the proportion to be closer to 1%.
After reviewing the number of workers in each of the Standard Industrial Classification codes of Arizona employers, the Committee concluded that Arizona's employment structure can be classified as less industrial than the average state. Therefore, the estimation of 4% will be used here as a conservative estimate of Arizona's employment structure, a figure that is conventionally cited by scientists.
Results
Non-Cancer Cases
According to the ICA there were 1,259,700 full-time workers in Arizona in 1991.
The number of reported illnesses was 2,519 statewide.
Thus, the reported annual occupational illness rate was two illnesses per 1,000 full time workers. This estimate does not include illnesses that occur among government employees or self-employed persons.
The highest rate among industrial divisions was experienced in manufacturing, where there were six illnesses per 1,000 employees.
Table 12.1 displays the specific categories of the 2,519 non-cancer illnesses.
Table 12.1 Occupational Illness In Arizona, 1991
---------------------------------------------------------- | Category | Number | Percent | | | | | | | | (%) | ========================================================== | Repeated trauma | 1347 | 53.5 | ---------------------------------------------------------- | Skin diseases | 408 | 16.2 | ---------------------------------------------------------- | Disorders due to physical agents | 73 | 2.9 | ---------------------------------------------------------- | Poisonings | 62 | 2.5 | ---------------------------------------------------------- | Resp. cond. due to toxic agents | 377 | 15 | ---------------------------------------------------------- | Dust diseases of the lung | 48 | 1.9 | ---------------------------------------------------------- | Death (non-cancer) | 0 | 0 | ---------------------------------------------------------- | Other | 201 | 8 | ----------------------------------------------------------
As shown in Table 12.1, repeated trauma (e.g., carpal tunnel syndrome) amounts to 53.5% of the reported illnesses. The remaining 46.4% are related to the workplace environment.
Cancer Cases
In 1993, there were 7,648 cancer deaths in Arizona due to all causes. Using the figure that 4% of these cancers are attributable to the workplace, the Committee estimates that 305 of these were occupationally-related.
Uncertainties in the Data
The estimates of non-cancer described above should be taken as the lower bound of the total incidence of occupational disease in Arizona. If the reporting requirements were more inclusive, we would expect the risk estimate to increase.
The recognition, recording, and reporting of non-cancer illness in Arizona is more straightforward than it is for cancer.
The present system of recording cancer cases and deaths does not yield a clear relationship between exposure to workplace toxins and cancer. The Committee's use of Doll and Peto's estimate, that 4% of cancers are related to the workplace, is widely accepted by scientists who study the causes of cancer.
However, Doll and Peto also state that the causes of many types of cancer are unknown. It is not known what proportion of these cases of unknown causes are really due to occupation. Moreover, it is not known whether the 4% estimate adopted for this risk estimate accurately reflects conditions in Arizona.
Many scientists today cite Doll and Peto's report on cancer risk, which was published in 1981. Over the years since then, there have been surprisingly few reviews of the etiology of cancer similar to it.
Since 1981, regulation and monitoring of many chemicals and processes have increased, resulting in less workplace exposures. Simultaneously, however, new technologies have introduced new and different chemicals into the workplace. It is unknown what effect many of these new chemicals will have on worker health in the future.
Hence, the true risk may be higher or lower. It is simply not known from the data that are currently available.
Conclusion
To get a better estimation of the risk of cancer related to toxins at the workplace, better data bases are needed. Better monitoring needs to be performed for specific chemicals at worksites.
Ideally, a data base should be devised that links industries and the chemicals they use. Every place of business should use a log or computer program that registers the employee names with the chemicals they use or potentially could use.
Employees should be educated regarding signs and symptoms of chemical exposures, and told to report adverse reactions swiftly to their medical departments.
When seeking medical attention employees should be able to state which chemicals they are using at work to allow a medical professional to search for a link to their illnesses.
Until Arizona devises a more detailed system of assessing, monitoring, tracking and evaluating the chemical toxins being used in industry, we can only speculate at the true risk of illness caused by these hazards.
Farm Worker Exposures To Pesticides
Scope
In recent years concerns have been voiced regarding potential adverse health effects from the agricultural use of pesticides. Pesticides are chemicals designed to kill or control unwanted pests such as insects, worms, and weeds. They are hazardous when they are improperly handled, mixed and applied, which can cause illnesses in workers.
Nationally, the EPA estimates between 20,000 illnesses each year are associated with the occupational use of pesticides on farms. This range is so great because the risks associated with pesticides and their uses vary.
Different pesticides have different levels of toxicity and rates of degradation. Some pesticides degrade into substances of greater or lesser toxicity than the original substance. Also, the signs and symptoms of acute poisoning may go unreported or misdiagnosed.
This report attempts to determine the health risks associated with the use of pesticides by Arizona farm workers.
Data Sources
The Committee first reviewed a 1993 General Accounting Office (GAO) report which assessed the monitoring activities for pesticides on Arizona farms, as well as the other 25 states that have monitoring programs for pesticides on farms.
The GAO study sought to identify and review all federal and state government monitoring systems by looking at data sources that provide information on pesticide- related occupational illnesses that occur in the farm sector.
The GAO study focused specifically on farm-related pesticide exposure cases that affect farmers, farm workers and others who handle pesticides on farms. They used surveys, case studies, and interviews to perform the study.
The Committee also used data from the Pesticide Poisoning and Surveillance Program at the ADHS. Since 1988, this program has required that all cases or suspected cases of pesticide illnesses in Arizona be reported to them.
The ADHS tracks illnesses reported to them directly, as well as those reported by the Poison Control Center, physicians and other health care professionals who suspect pesticide illness. Data from the Pesticide Poisoning and Surveillance Program show the results of investigations conducted over the past two years.
Other data sources used include:
o A 1994 report from the Arizona Department of Agriculture's Safety Office, which shows an approximate number of Arizona farm workers, approximately how many acres they harvest, and the type and amount of some of the pesticides they use
o A sales survey by the Council of Environmental Studies in Tucson
o Information provided by the EPA Office of Pesticide Programs - Occupational and Residential Exposure Division
Results
The Committee's review of the various sources produced little solid information to document to number of farm workers being poisoned by use of pesticides in Arizona. In fact, it was even difficult to quantify the use of pesticides.
According to the GAO report, and results of a self-imposed audit conducted by the ADHS in 1989, under-reporting of suspected pesticide related illnesses was found to be a serious problem with the existing monitoring system at that time.
Although 48 cases were recorded by the reporting system from early 1987 through mid-1989, investigators identified a large number of cases that were not reported to the state system. These included 35 cases treated by health care professionals in Mexico, and 49 complaints of pesticide-related health effects reported to other agencies in the state.
The number of reports received and confirmed by the ADHS has not changed in the years since the reporting law went into effect. Although the ADHS responds to hundreds of inquiries each year, and they investigated about 40 incidents each year since 1988, the number of confirmed pesticide poisonings was:
o 3 in 1988
o 5 in 1989
o 4 in 1990
o 2 in 1991
o 1 in 1992
o 4 in 1993
As Table 12.2 shows, of the 32 suspected poisonings in 1993, only 14 were agriculturally related. Moreover, of these 14, only four were confirmed.
Table 12.2 Non-Cancer Cases in Arizona, 1993
---------------------------------------------------------------------- | Number and Type of Case | Number Agriculturally-Related | ====================================================================== | 8 confirmed pesticide poisonings | 4 | ---------------------------------------------------------------------- | 9 probable pesticide poisonings | 6 | ---------------------------------------------------------------------- | 15 possible pesticide poisonings | 4 | ----------------------------------------------------------------------
The Arizona Department of Agriculture (ADA) issues cards to farm workers who have received general training about pesticide safety, as required by the EPA. According to the Office of Safety at the ADA, in 1995, there were 66,695 cards issued to Arizona farm workers who may be exposed to pesticides at some point during the planting, growing, and harvesting cycle. This estimate includes seasonal and migrant workers as well as those workers who may be employed just one or two days per year. The ADA issued 22,295 cards to pesticide handlers, that is, those who mix and apply the pesticides.
The ADA also investigates reports of possible misapplication, which may or may not be associated with farm worker safety.
In the U.S., there are an estimated five million farm workers in the U.S. Arizona's known 66,000 workers would comprise about 1% of the national total. If there are 20,000 estimated pesticide-related illness each year nationwide, Arizona should have approximately 1% of these, or about 200 cases. However, the data reported to Arizona's state agencies for the latest years shows much fewer numbers. Either Arizona workers are markedly safer than workers in other parts of the U.S., or there is substantial under-reporting of cases in Arizona.
One approach to evaluating the low number of Arizona cases is to compare the number of poisonings reported in California, which has a more accurate reporting system. Data from reports to California's poison control centers show that there are about one to three occurrences of poisoning for every 1,000 pesticide applications (EPA, 1994).
Pesticide handlers and field workers both reported instances of poisoning. The EPA report ranked the pesticides according to their risk to agriculture workers and found that the top six pesticides were:
o Mevinphos
o Carbofuran
o Methamidophos
o Methomyl
o Aldicarb
o Azinphosmethyl
According to a sales survey from Tucson, Arizona, there are some general trends occurring in Arizona in relation to the amount of pesticides sold to the state. These trends include:
o Insecticide sales decreased from 1991 to 1992
o Defoliants, desiccants and growth regulator sales were lower than 1991, but higher than 1989 and 1990
o Herbicide sales were up slightly from 1991 sales
o Fumigant sales dropped considerably (following a consistent four-year trend)
o Fungicide sales were over double what they were in 1991
This survey was voluntary with 13 of the top pesticide vendors responding. The study, however, does not depict usage.
Summary of Theoretical Cancer Risks
There is a theoretical cancer risk from dermal exposure to the four pesticides that are used in significant quantities by cotton growers in Arizona. These pesticides are considered probable human carcinogens. The estimated farm worker population exposed to each of the four chemicals is 1100 persons.
Because the actual number of employees who are pesticide mixers/loaders is not tabulated in Arizona, the estimated population sizes of 1100 persons was used. As a general rule, there will be no more than one mixer/loader person per pesticide applicator.
Using these estimated population numbers may greatly over or under estimate the actual number of excess cancers. Until Arizona compiles and categorizes the actual numbers of employees in these areas, estimates will have to be used.
Discussion
Even today under-reporting appears to be a problem. Current exposure data indicate that only a small percentage of workers experience acute exposures that exceed acceptable levels.
For the number and percentage of farm workers in Arizona, it is expected that there should be approximately 200 reported illnesses instead of the reported 14 agriculturally-related illnesses, only four of which were confirmed.
Chronic exposures to indicator pesticides could be associated with some additional cancers and some non-cancer morbidity.
The dose a worker will be exposed to depends on what he or she does with the pesticide (mix/load, apply, or some other job).
The formula used in this study assumes that every mixer/loader or applicator handles these pesticides every working day for eight hours per day, which is unlikely. It is more likely that they will work with these chemicals more on some days and less or not at all on other days. Also, they will likely be exposed to pesticides other than those pesticides which are not shown to cause cancer in humans at this time.
Exposure estimates are based on actual monitoring data if available. However, adequate toxicology data for many pesticides are often lacking, particularly the characterization of acute risks among the most highly exposed.
The cumulative contribution of total intake of carcinogenic pesticides to lifetime cancer risks is also poorly described.
The potential health impacts of multiple, synergistic or cumulative exposures are not well characterized, but such exposures occur and may pose significant health risks. For instance, this study assesses cancer risk from dermal exposure and not from inhalation exposure, but these two types of exposures sometimes occur together. Yet it is not understood how one exposure may effect another to impact health.
Arizona does not currently compile exposure data on farm workers who use pesticides. Therefore, this report relied upon national data. However, using national data to establish exposure estimates and risk may produce misleading results. The true risk may be greater or less than shown here, or it may be zero.
Arizona farm workers reportedly use irrigation ditches to bathe, cool off, or even as a source of drinking water. Currently, there is no monitoring of the levels of pesticides in these canals, even when the canals are used to remove excess water from sprayed fields. It is not known what the levels of exposure are to workers nor to streams to which the return flows are sent.
The selected indicator pesticides used in this report represent only a small percentage of the total and cumulative pesticide exposure. Theoretical cancer burden estimates, for example, are based on exposures to a few potentially carcinogenic pesticides, while the EPA has identified over 60 agricultural pesticides that are potentially carcinogenic.
Change is forthcoming:
o The Arizona Department of Agriculture and Safety Office is to begin gathering data on farm worker exposure to pesticides in the near future.
o Even now under the new worker protection laws, training is taking place in an attempt to educate the workers on safely using and handling pesticides. The workers learn how to protect themselves, to identify the signs and symptoms of pesticide illness, and to effectively handle a medical emergency.
o The Federal Insecticide, Fungicide and Rodenticide Act is demanding that the workers don more protective clothing to decrease dermal exposures. It is not clear, however, how this will be enforced.
Birth Defects
The public is concerned about the role of pesticides and adverse reproductive outcomes in farm workers. There are only a few studies on this topic, and none has been conducted in Arizona.
The literature contains a number of studies that consistently find that farm work is a risk factor for fetal death and birth defects. For example, an increased prevalence of neural tube defects was observed in areas with heavy use of agricultural pesticides. Similarly, limb-reduction defects and cleft lip have been reported as defects occurring at higher rates among the offspring of farm workers.
It is important to note, however, that other studies fail to show any link to pesticides. For example, a study of crop dusters and non-pesticide-exposed siblings showed no difference in the prevalence of birth defects in offspring or spontaneous abortions in their wives.
When elevated, the relative rates of adverse reproductive outcomes tend to be modestly elevated (compared to other occupational groups). At the present time, the Committee is unable to translate these rates into an estimate of the number of events occurring among Arizona farm workers.
The seasonal and highly mobile nature of farm workers makes studies of adverse reproductive outcomes difficult to conduct. Also, these workers are at the low end of the socioeconomic scale, making it difficult for them to obtain access to early prenatal care.
Conclusion
To gauge the precise number of farm workers who may be potentially exposed to pesticides is difficult since our agricultural workers are migratory and sometimes undocumented aliens.
However, an effort to document the number of farm workers employed needs to be put forth. Until we know the exposed population, we will have to rely on estimates for cancer risks and non-cancer morbidity risks.
It appears our monitoring system is still not reflecting the true picture of pesticide related illnesses in Arizona.
The safety and protection of the workers needs to take a higher priority in the future. For example:
o Better education for the farm workers as well as medical professionals needs to be done.
o Medical professionals need to better understand the signs and symptoms of pesticide illness to be able to diagnose better and render treatment more quickly.
o While efforts at training and education are being made, this is only a small part of a solid comprehensive pesticide monitoring program.
o Better inventory and tracking of particular pesticides and the amounts used of each must be documented.
Finally, more research needs to be conducted regarding the adverse health effects from synergistic or cumulative exposures.