LETTERS TO THE EDITOR
would assume that there are no lives being saved because of ROPS. Yet I know much better since I have information on at least 35 overturn incidents in Nebraska where ROPS were in place and lives saved. This was done as part of the voluntary program in Nebraska and not because of a government requirement. Without ROPS, 40 per cent of the operators of the tractor overturns should have been killed. This figure is taken from a Nebraska overturn study that was started in 1966, 10 years before the OSHA standard came into being. That study has been continued since 1966. I know how the accidents happened since staff of the Department of Agricultural Engineering were involved in researching the site of the tractor overturns. I am familiar with the history of roll over protective structures. The Department of Agricultural Engineering at the University of Nebraska played an important part in the development of ROPS. Also, I served as chairman of the Agricultural Advisory Committee to OSHA that developed the OSHA ROPS standard. My opposition to authors Karlson and Noren's conclusion is that they say the voluntary standard movement is not working. That is not true. It has worked and I have the statistics to show that it has. My concern with this report is that it will show up in future references alluding that voluntary standards have failed. This is not true. Voluntary standards are a vital part in making agricultural employment safer. Rollin D. Schnieder Extension Safety Specialist Dept. ofAgricultural Engineering Cooperative Extension Service University of Nebraska
Karlson and Noren should be complimented for their study of tractor fatalities which appeared in the February, 1979 issue of the America Journal of Public Health. Agricultural accident problem areas have not gotten their fair share of attention from researchersparticularly when considering the number and severity of the problems that exist. For those not well versed in the areas of agricultural and accident re824
search, words of caution are in order about their study. The authors' failure to define "voluntary safety standards" leads to confusion of the issues involved. Their thesis is that "voluntary safety standards have failed." Yet nowhere in their study do they present evidence that people are being killed because a ROPS was not strong enough, bolts were breaking from anchorage points, etc. Their premise seems to be that people are not voluntarily buying and using enough of the safety equipment being made available and an increasing accidental death rate is the result. That is a meaning far different from that embodied in the term "failure of voluntary safety standards." Much of the authors' conclusion seems to be based on the directional changes noted in the tractor accident death rates. Any of a number of factors could produce this statistical variation and, thus, lead to erroneous conclusions. Collapsing data, interpolation and extrapolation provide opportunities for statistical error and trend distortion to creep in. Changes in the accuracy of determining and reporting cause of death and/or census data could produce interpretation error. And one must question the validity of using an accidental death rate as a means of comparison-deaths per million man hours of tractor use would provide a much more valid comparison. Even if subsequent analyses were to validate the statistical trend, there is little justification to generalize these findings on a national basis. The researcher must keep in mind the tremendous diversity that exists in American agriculture and the rate of machinery replacement. That which is found in Wisconsin-particularly one 4-county area-is but one sample. The researchers' major recommendation for remedial action-that all tractors sold be required to have ROPS installed-might be supportable on an opinion basis and is worthy of consideration. But the authors' apparent failure to consider the practical problems involved with implementing such a recommendation, in addition to basing it on unvalidated, over-generalized data, detracts from any scientific support for such a proposal.
Gary Erisman, PhD Extension Safety Leader Florida Cooperative Extension Service University of Florida Institute of Food and Agricultural Sciences
Authors' Response In Wisconsin, the injury death rate associated with tractors on farms increased from 10.9/100,000 male farm residents during 1961-1965 to 13.6/ 100,000 during 1971-1975 (p < .05). Deaths associated with overturning tractors were most common, with death rates of 6/100,000 male farm residents for 1961-1975. Pfister, Erisman and Schnieder disagree with our conclusion that voluntary safety efforts failed to protect male farm residents from death due to tractor-related in-
juries. Pfister's argument is that increased death rates merely reflect increased exposure to tractors. That may be, however, it does not change the fact that a Wisconsin farmer in 1975 was at greater risk of dying from a tractor-related injury than a farmer in 1961. It is clear that voluntary standards were not adequate to ensure that occupant protection kept up with increased tractor use, or with other risks which may have increased during the time period. Actually, as exposure to an injury- or disease-producing agent increases, the size of the public health problem it presents will increase as well. More exposure to tractors, therefore, argues for, rather than against, the need for improved safety standards. As Erisman points out, our concern is not with the adequacy of the industry-set standards for operator protection, but with their voluntary nature. Manufacturers can choose whether or not to follow the standards and farmers have chosen not to use tractors so equipped in large enough numbers to lower death rates in the population. We stand by our statement: voluntary standards have failed. Erisman is also concerned with our use of death rates per capita. We justify our choice with two reasons: exposure data for Wisconsin do not exist and, furthermore, they are not essential factors in AJPH August 1979, Vol. 69, No. 8
LETTERS TO THE EDITOR
the basic public health issue of individual risk of death over time. He says "any number of factors" could contribute to the increase in death rates; it is more relevant to point out that voluntary safety standards have not achieved the intended decrease in death rates. Regarding the issue of generalizability, farming in Wisconsin is similar to that in other midwestern states. Although large farms (employing ten or more people) must comply with mandatory OSHA ROPS standards, smaller farms contribute heavily to the total industry and Wisconsin farms are quite representative of this inadequately protected agricultural subgroup. Schnieder says there are 850,000 rollover protective structures (ROPS) in use on agricultural tractors. This covers only 19 per cent of the tractors in the U.S.* In Wisconsin, many new tractors are still being sold without ROPS. Regarding his comments about our data sources: while death certificates often do not provide much detail on the injury event and do not include non-fatal injuries, they are the only source for injury data which covers the entire male farm population of Wisconsin. Health statistics such as these are appropriate for studies such as ours which concern the health status of a population. We are in wholehearted agreement with Schnieder that ROPS save lives; the point of our paper is that they need to be used more frequently. Current OSHA exemptions work against this. The enormous social and economic impact of the death of a farmer or farm family member justifies pursuing increased governmental regulation so that industry safety standards are applied more rapidly and more broadly than is currently the case. Trudy Karlson, MS Project Director Facial Injury Project Jay Noren, MD, MPH Assistant Professor Centerfor Health Systems Research and Analysis University of Wisconsin 1225 Observatory Drive Madison, WI53706 *4,467,378 tractors in U.S. in 1974, ac-
cording to the Census of Agriculture. AJPH August 1979, Vol. 69, No. 8
Two Comments Received On LA Study of Physician Malpractice Slowdown Dr. James J. James concludes his study of the Los Angeles physician malpractice slowdown (AJPH, May 1979) by stating that the strike was responsible for more deaths prevented than lives lost. This interpretation was based on his finding that the empirical estimates of deaths due to delay in treating patients was exceeded by the lower mortality due to elective surgery not being performed, given estimates of the volume of elective surgery that would otherwise have been performed and the elective surgical mortality rate. Dr. James has overlooked the postponability characteristic of elective surgery. The most reasonable assumption is that the elective surgeries not undertaken during the slowdown period were performed shortly afterward. These briefly deferred deaths cannot be subtracted from the estimates of deaths due to treatment delay to arrive at a net estimate of deaths due to physician unavailability, unless the author is willing to argue that the treatment delay deaths too were only briefly postponable. If this were argued the mortality issue would be trivial. Dr. James' evidence taken at face value can only lead to an interpretation opposite to that presented by him; namely, that the physician malpractice slowdown did increase mortality. Jerome Joffe, PhD Senior Research Associate Blue Cross/Blue Shield of Greater New York 622 Third Avenue New York, NY 10017
The report by Dr. James J. James on "Impacts of the Medical Malpractice Slowdown in Los Angeles County: January 1976" in the May 1979 Journal, makes many useful contributions to our knowledge, but certain omissions conceal important inferences which may be drawn from this experience. First, Dr. James seems to have overlooked the technical fact that
weekly mortality tabulations in Los Angeles County are based on the date of recording, not date of occurrence. The delay between these two dates, according to the person in charge of these vital statistics, is about 10-14 days. Second, Dr. James terminates his data presentation at the seventh week of the year. In light of the lag noted above, this would be about equivalent to the final week of the 35-day slowdown. He does not carry the analysis beyond this week. In a parallel study of the January 1976 doctor slowdown in Los Angeles County, to be reported elsewhere,* my findings-on the basis of mortality data from the Los Angeles County Department of Health Services were as follows: Deaths per 100,000 per Week Week
Mean for 1971-75
1976
1
15.2
21
2
21.8
21
3
21.4
20
4
5 6 7 8
20.6 19.2 18.4 20.0 19.4
17 17 13 14 26
9
22.4
20
10
19.0
18
11
17.6
19
12
17.4
19
Comment
Lag in death recording Lag in death recording Onset of doctor slowdown Slowdown Slowdown Slowdown Slowdown Return to normal surgery Return to normal surgery Return to normal surgery Return to normal surgery Return to normal surgery
As Dr. James points out, the doctor slowdown was very selective; primary care was not withheld until about the last week. Emergency surgery was provided throughout the period as necessary. The withdrawal of services, therefore, was almost exclusively applicable to elective surgery. It is noteworthy that Dr. James states toward the end of his paper that "coupled with the estimated number of *To be published in Social Science and Medicine, Summer 1979.
825
would assume that there are no lives being saved because of ROPS. Yet I know much better since I have information on at least 35 overturn incidents in Nebraska where ROPS were in place and lives saved. This was done as part of the voluntary program in Nebraska and not because of a government requirement. Without ROPS, 40 per cent of the operators of the tractor overturns should have been killed. This figure is taken from a Nebraska overturn study that was started in 1966, 10 years before the OSHA standard came into being. That study has been continued since 1966. I know how the accidents happened since staff of the Department of Agricultural Engineering were involved in researching the site of the tractor overturns. I am familiar with the history of roll over protective structures. The Department of Agricultural Engineering at the University of Nebraska played an important part in the development of ROPS. Also, I served as chairman of the Agricultural Advisory Committee to OSHA that developed the OSHA ROPS standard. My opposition to authors Karlson and Noren's conclusion is that they say the voluntary standard movement is not working. That is not true. It has worked and I have the statistics to show that it has. My concern with this report is that it will show up in future references alluding that voluntary standards have failed. This is not true. Voluntary standards are a vital part in making agricultural employment safer. Rollin D. Schnieder Extension Safety Specialist Dept. ofAgricultural Engineering Cooperative Extension Service University of Nebraska
Karlson and Noren should be complimented for their study of tractor fatalities which appeared in the February, 1979 issue of the America Journal of Public Health. Agricultural accident problem areas have not gotten their fair share of attention from researchersparticularly when considering the number and severity of the problems that exist. For those not well versed in the areas of agricultural and accident re824
search, words of caution are in order about their study. The authors' failure to define "voluntary safety standards" leads to confusion of the issues involved. Their thesis is that "voluntary safety standards have failed." Yet nowhere in their study do they present evidence that people are being killed because a ROPS was not strong enough, bolts were breaking from anchorage points, etc. Their premise seems to be that people are not voluntarily buying and using enough of the safety equipment being made available and an increasing accidental death rate is the result. That is a meaning far different from that embodied in the term "failure of voluntary safety standards." Much of the authors' conclusion seems to be based on the directional changes noted in the tractor accident death rates. Any of a number of factors could produce this statistical variation and, thus, lead to erroneous conclusions. Collapsing data, interpolation and extrapolation provide opportunities for statistical error and trend distortion to creep in. Changes in the accuracy of determining and reporting cause of death and/or census data could produce interpretation error. And one must question the validity of using an accidental death rate as a means of comparison-deaths per million man hours of tractor use would provide a much more valid comparison. Even if subsequent analyses were to validate the statistical trend, there is little justification to generalize these findings on a national basis. The researcher must keep in mind the tremendous diversity that exists in American agriculture and the rate of machinery replacement. That which is found in Wisconsin-particularly one 4-county area-is but one sample. The researchers' major recommendation for remedial action-that all tractors sold be required to have ROPS installed-might be supportable on an opinion basis and is worthy of consideration. But the authors' apparent failure to consider the practical problems involved with implementing such a recommendation, in addition to basing it on unvalidated, over-generalized data, detracts from any scientific support for such a proposal.
Gary Erisman, PhD Extension Safety Leader Florida Cooperative Extension Service University of Florida Institute of Food and Agricultural Sciences
Authors' Response In Wisconsin, the injury death rate associated with tractors on farms increased from 10.9/100,000 male farm residents during 1961-1965 to 13.6/ 100,000 during 1971-1975 (p < .05). Deaths associated with overturning tractors were most common, with death rates of 6/100,000 male farm residents for 1961-1975. Pfister, Erisman and Schnieder disagree with our conclusion that voluntary safety efforts failed to protect male farm residents from death due to tractor-related in-
juries. Pfister's argument is that increased death rates merely reflect increased exposure to tractors. That may be, however, it does not change the fact that a Wisconsin farmer in 1975 was at greater risk of dying from a tractor-related injury than a farmer in 1961. It is clear that voluntary standards were not adequate to ensure that occupant protection kept up with increased tractor use, or with other risks which may have increased during the time period. Actually, as exposure to an injury- or disease-producing agent increases, the size of the public health problem it presents will increase as well. More exposure to tractors, therefore, argues for, rather than against, the need for improved safety standards. As Erisman points out, our concern is not with the adequacy of the industry-set standards for operator protection, but with their voluntary nature. Manufacturers can choose whether or not to follow the standards and farmers have chosen not to use tractors so equipped in large enough numbers to lower death rates in the population. We stand by our statement: voluntary standards have failed. Erisman is also concerned with our use of death rates per capita. We justify our choice with two reasons: exposure data for Wisconsin do not exist and, furthermore, they are not essential factors in AJPH August 1979, Vol. 69, No. 8
LETTERS TO THE EDITOR
the basic public health issue of individual risk of death over time. He says "any number of factors" could contribute to the increase in death rates; it is more relevant to point out that voluntary safety standards have not achieved the intended decrease in death rates. Regarding the issue of generalizability, farming in Wisconsin is similar to that in other midwestern states. Although large farms (employing ten or more people) must comply with mandatory OSHA ROPS standards, smaller farms contribute heavily to the total industry and Wisconsin farms are quite representative of this inadequately protected agricultural subgroup. Schnieder says there are 850,000 rollover protective structures (ROPS) in use on agricultural tractors. This covers only 19 per cent of the tractors in the U.S.* In Wisconsin, many new tractors are still being sold without ROPS. Regarding his comments about our data sources: while death certificates often do not provide much detail on the injury event and do not include non-fatal injuries, they are the only source for injury data which covers the entire male farm population of Wisconsin. Health statistics such as these are appropriate for studies such as ours which concern the health status of a population. We are in wholehearted agreement with Schnieder that ROPS save lives; the point of our paper is that they need to be used more frequently. Current OSHA exemptions work against this. The enormous social and economic impact of the death of a farmer or farm family member justifies pursuing increased governmental regulation so that industry safety standards are applied more rapidly and more broadly than is currently the case. Trudy Karlson, MS Project Director Facial Injury Project Jay Noren, MD, MPH Assistant Professor Centerfor Health Systems Research and Analysis University of Wisconsin 1225 Observatory Drive Madison, WI53706 *4,467,378 tractors in U.S. in 1974, ac-
cording to the Census of Agriculture. AJPH August 1979, Vol. 69, No. 8
Two Comments Received On LA Study of Physician Malpractice Slowdown Dr. James J. James concludes his study of the Los Angeles physician malpractice slowdown (AJPH, May 1979) by stating that the strike was responsible for more deaths prevented than lives lost. This interpretation was based on his finding that the empirical estimates of deaths due to delay in treating patients was exceeded by the lower mortality due to elective surgery not being performed, given estimates of the volume of elective surgery that would otherwise have been performed and the elective surgical mortality rate. Dr. James has overlooked the postponability characteristic of elective surgery. The most reasonable assumption is that the elective surgeries not undertaken during the slowdown period were performed shortly afterward. These briefly deferred deaths cannot be subtracted from the estimates of deaths due to treatment delay to arrive at a net estimate of deaths due to physician unavailability, unless the author is willing to argue that the treatment delay deaths too were only briefly postponable. If this were argued the mortality issue would be trivial. Dr. James' evidence taken at face value can only lead to an interpretation opposite to that presented by him; namely, that the physician malpractice slowdown did increase mortality. Jerome Joffe, PhD Senior Research Associate Blue Cross/Blue Shield of Greater New York 622 Third Avenue New York, NY 10017
The report by Dr. James J. James on "Impacts of the Medical Malpractice Slowdown in Los Angeles County: January 1976" in the May 1979 Journal, makes many useful contributions to our knowledge, but certain omissions conceal important inferences which may be drawn from this experience. First, Dr. James seems to have overlooked the technical fact that
weekly mortality tabulations in Los Angeles County are based on the date of recording, not date of occurrence. The delay between these two dates, according to the person in charge of these vital statistics, is about 10-14 days. Second, Dr. James terminates his data presentation at the seventh week of the year. In light of the lag noted above, this would be about equivalent to the final week of the 35-day slowdown. He does not carry the analysis beyond this week. In a parallel study of the January 1976 doctor slowdown in Los Angeles County, to be reported elsewhere,* my findings-on the basis of mortality data from the Los Angeles County Department of Health Services were as follows: Deaths per 100,000 per Week Week
Mean for 1971-75
1976
1
15.2
21
2
21.8
21
3
21.4
20
4
5 6 7 8
20.6 19.2 18.4 20.0 19.4
17 17 13 14 26
9
22.4
20
10
19.0
18
11
17.6
19
12
17.4
19
Comment
Lag in death recording Lag in death recording Onset of doctor slowdown Slowdown Slowdown Slowdown Slowdown Return to normal surgery Return to normal surgery Return to normal surgery Return to normal surgery Return to normal surgery
As Dr. James points out, the doctor slowdown was very selective; primary care was not withheld until about the last week. Emergency surgery was provided throughout the period as necessary. The withdrawal of services, therefore, was almost exclusively applicable to elective surgery. It is noteworthy that Dr. James states toward the end of his paper that "coupled with the estimated number of *To be published in Social Science and Medicine, Summer 1979.
825
