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DateLine Sunday, 9 September 2007

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Body & Soul Compiled by Shanika Sriyananda
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The impact of pesticide regulations on suicide

In the early 1990s Sri Lanka had one of the highest suicide rates in the world. Between 1950 and 1995 rates increased 8-fold to a peak of 47 per 100 000 in 1995. In the 10 years after 1995, Sri Lanka's suicide rates declined by 50%.

Understanding the reasons for this transformation in the incidence of suicide in Sri Lanka may have important implications for suicide prevention in other low and middle-income countries.

Pesticide self-poisoning is one of the most commonly used methods of suicide in Asia with an estimated 300,000 deaths each year.

Previous research indicates that pesticide poisoning accounts for two-thirds of Sri Lanka's suicide deaths. Case-fatality following pesticide self-poisoning can be over 50 times higher than following paracetamol poisoning, the most commonly used method of self-poisoning in Britain and other developed countries.

The use of pesticides in acts of self-harm may therefore have profound effects on the epidemiology of suicide in countries where pesticides are commonly ingested in acts of self-poisoning.

We hypothesized that Sri Lanka's robust approach to banning the most toxic pesticides in the 1980s and 90s contributed to its fall in suicide mortality between 1995 and 2005.

We obtained data on the number of suicides in Sri Lanka from the following sources:

(i) total suicides and suicide rates between 1940 and 1975 from two previous analyses of suicide in Sri Lanka both based on data from Sri Lanka's Registrar General

(ii) age-, sex-and method-specific suicide data from 1975 to 2005 from the Department of Police, Division of Statistics, Sri Lanka.

For most of the time period covered by the data on method specific suicides (1975?96) the method of death was categorized into one of eight groups: poisoning/acetic acid, hanging, jumping in front of a train, drowning, burning, shooting, use of sharp cutting instruments and 'other means'. Since the terms 'acetic acid' and 'poisoning' were used interchangeably up to 1996, we have categorized both as poisoning.

In 1997, the number of specific methods of suicide was expanded to include pesticide poisoning and in 2002 six additional categories were added (explosives, ingestion of acids, ingestion of fuel, plant poisoning, jumping from a height and addictive drug ingestion/injection). The most commonly recorded method of suicide in the study period was 'other means' - accounting for 38% of all suicides.

Reasons

We have four reasons to believe those coded as 'other' were mainly deaths from self-poisoning.

First, in 2 years when the numbers of poisonings doubled (1983 and 1984) the number of suicide coded as 'other' halved, but there was no effect on the numbers of suicides using other specified methods (hanging, etc.).

Second, previous studies of suicide in Sri Lanka in the 1980s and 1990s indicate that the principle method used for suicide is self-poisoning.

Third, as noted earlier, pesticide suicides were categorized as a separate specific method of suicide from 1997 onwards and in that year 2589 pesticide suicide deaths were recorded.

In the same year the total number of 'poisoning' suicides dropped from 1954 in 1996 to 231; likewise the number of deaths coded as due to 'other means' declined from 3818 in 1996 to 2027 in 1997 and 1397 in 1998, and continued to decline to 31 by 2005.

At this time, no other specific methods of suicide showed a marked increase in numbers. This suggests that most, if not all, the 'transfer' from 'other means' to specific means was to the pesticide poisoning category.

Lastly, for the period covered by our analysis, the specific methods of suicide listed in the mortality data were self-poisoning (acetic acid), hanging, drowning, self-burning, firearms, self-piercing or jumping in front of a train - and that these seven methods account for over 90% of suicide deaths in most countries.

The 'other' category, therefore, is unlikely to consist of a different (unspecified) method. Based on these observations, in our analysis of trends in method-specific suicide rates, we combined 'other' and 'all self-poisoning' categories into a single class - self-poisoning.

To assess whether any changes in suicides were due to declines in pesticide self-poisoning, we obtained data on the number of hospital admissions for pesticide poisoning and the number of in-hospital deaths from pesticide poisoning throughout the whole of Sri Lanka from published sources and from Sri Lanka's Health Statistics Unit 1980?2003 (Colombo).

To estimate age- and sex-specific suicide rates we used estimated mid-year population data (in 5 year age/sex bands) obtained from the Registrar General for Sri Lanka.

Trends in national suicide rates are adversely influenced by economic recession/unemployment as well as rises in levels of divorce and alcohol misuse.

We obtained data on levels of unemployment between 1971 and 2005 from figures published by the Central Bank of Sri Lanka. To investigate trends in the use and misuse of alcohol we obtained data on trends in alcohol consumption and cirrhosis mortality from Sri Lanka's Department of Census and Statistics. We used information in published papers to assess trends in divorce in Sri Lanka.

Periods of war tend to be associated with reductions in suicide. There has been a longstanding civil war in Sri Lanka.

To assess whether there were changes in the total amount of pesticides available in Sri Lanka we obtained published data on pesticide imports and consumption in Sri Lanka (1995-2000).

Four further initiatives that may have influenced suicide rates in Sri Lanka were:

(i) the Control of Pesticides Act that created the position of the 'Registrar of Pesticides' in 1983 - this post carries the authority to set regulations and standards for pesticides;

(ii) the establishment of National Poisons Information Centre in 1988

(iii) the creation of the Presidential Task Force on Suicide, which developed a National Policy and Action Plan on the Prevention of Suicide published in December 1997 and

(iv) the de-criminalization of suicide in Sri Lanka in 1998.

We used graphical approaches to investigate secular trends in age-, sex- and method-specific suicide rates.

We related these trends to the timing of specific interventions by Sri Lanka's Registrar of Pesticides.From the late 1970s until the early 1990s, WHO Class I ('extremely or highly toxic') organophosphorus (OP) insecticides such as parathion, methyl parathion, monocrotophos and methamidophos were the commonest poisons taken in fatal self-harm.

The Registrar of Pesticides banned methyl parathion and parathion in 1984 and over the following years gradually phased out all the remaining Class I organophosphate pesticides, culminating in July 1995 with bans on the remaining Class I pesticides monocrotphos and methamidophos.

During this transitional period, farmers switched their agricultural practice to the Class II ('moderately hazardous') organochlorine pesticide, endosulfan, which proved clinically to be highly toxic. Imports of endosulfan were banned in December 1998.

Sri Lanka's suicide rates rose gradually from 6.3 per 100 000 in 1940 to 9.9 per 100 000 in 1960. Thereafter, the rate of suicide increased more sharply, doubling between 1961 and 1971 and doubling again between 1971 and 1983, before reaching a peak of 47 per 100 000 in 1995.

The period of rapid rise in suicides in the late 1950s and early 1960s coincided with the first reported cases of pesticide-associated deaths in Sri Lanka. There were brief interruptions to this year on year rise in 1975-78 and in 1990-94.

Rates halved between 1995 and 2005. There were 19,769 fewer suicides in 1996-2005 as compared with 1986-1995. In 1975, age standardized suicide rates were 25.9 per 100 000 in males and 10.9 per 100 000 in females. Rates rose by 3-fold in both sexes to a peak in 1995 of 77.9 per 100 000 in males and 27.8 per 100 000 in females. Subsequently rates halved in both sexes.

By 2005, suicide rates were 37.3 per 100 000 and 9.7 per 100 000 in males and females, respectively. The highest rates occurred between 1987 and 1995 in both men and women and the timing of the reduction in rates was identical.

There appeared to be little impact on suicides of the bans placed on methyl parathion and parathion in 1984, other than perhaps a slowing of the rapid rise in suicide rate noticed between 1961 and 1983.

Ban

However, the ban on the final permitted class I pesticides methamidophos and monocrotophos (1995) and the class II pesticide endosulfan (1998) were both followed by marked reductions in overall suicides.

The National Suicide Prevention Policy (December 1997) post-dated the decline in suicides and the National Poisons Information Centre was introduced 7 years before the suicide reductions commenced (1988). The method-specific suicide data indicate that the reduction in suicide occurred largely as a consequence of a reduction in self-poisoning and 'other' methods of suicide.

* * This interpretation is supported by hospital mortality data which show that in-hospital death rates from pesticide self poisoning halved from 12.0 per 100 000 in 1998 to 6.5 per 100 000 in 2005.

By 2005, in-hospital pesticide poisoning mortality rates (6.5 per 100 000) were lower than they had been in 1975 (6.9 per 100 000). Of note, however, there was a rise in in-hospital pesticide poisoning deaths from 8.7 per 100 000 in 1995 to 12.0 in 1998 following the 1995 ban on Class I pesticides.

The reduction in suicides was not due to a reduction in levels of self-poisoning. Between 1993 and 1995. 47,411 people were admitted to hospital following pesticide poisoning (accidental and deliberate), this number increased by 16% to 55,160 in 2003-05.

Furthermore, the reduction in suicides was not due to the reduced overall availability of pesticides. In 1995, 1736 metric tones of insecticides, herbicides and fungicides were used in Sri Lanka, this amount decreased only slightly (by 2%) to 1696 metric tons in 2000.

The period of rapid rise in Sri Lanka's suicide rate coincided with the emergence of the first reported cases of pesticide poisoning and a rapid rise in pesticide-related deaths between 1954 and 1963. Around this period the proportion of suicides due to poisoning increased from 37% (1959) to 72% (1969).

The marked decline in Sri Lanka's suicide rates in the mid-1990s coincided with the culmination of a series of legislative activities that systematically banned the most highly toxic pesticides that had been responsible for the majority of pesticide deaths in the preceding two decades.

Other, earlier measures, such as the 1980 Control of Pesticides Act and the establishment of the National Poisons Information Centre in 1988 may have contributed to the levelling off of the epidemic rise in suicide in the 1970s but preceded the marked reductions by over 10 years.

The impact of the import bans in 1995 and 1998 on the pesticides used for self-poisoning are seen in two studies documenting changes in the pesticides ingested in acts of self-poisoning in Sri Lanka.

Following the ban on Class I pesticides, there was a rise in the use of endosulfan for self-poisoning and a marked reduction in the use of Class I pesticides. The last cases of class I pesticide poisoning deaths were seen in 1997 in Anuradhapura and 1999 in southern Sri Lanka. Endosulfan fatalities had declined markedly by 2000 in Anuradhapura and by 2002 in southern Sri Lanka from peaks in 1997/1998.

Before accepting that the reduction in suicide is the result of Sri Lanka's restrictions on the sales of toxic pesticides it is important to review alternative explanations. We found no evidence that the trends were specifically associated with beneficial changes in levels of employment, alcohol sales, divorce or with periods of civil war.

The effects of any improvements in the recognition and treatment of depression following the Presidential Task Force's report on suicide in 1997 are not possible to assess, but its publication post-dated the large fall in suicides between 1995 and 1997 and we are aware of no national mental health initiatives in Sri Lanka that are likely to have resulted in the observed 50% reduction in suicide.

Whilst deaths by self-poisoning and 'other' methods of suicide declined after 1995, the number of hospital admissions for self-poisoning continued to rise indicating either a reduction in the toxicity of the agents consumed or an improvement in their medical management.

Pesticides are one of the most frequently used methods of suicide worldwide.

Strategies

For this reason, strategies to reduce pesticide self-poisoning deaths may have a major impact on global patterns of suicide.

A number of strategies have been suggested to reduce these deaths. Our data suggest that restricting the availability of toxic pesticides should be prioritised. We propose other countries such as China and India, where pesticide self-poisoning is a major health problem, follow Sri Lanka's example in comprehensively regulating pesticide imports and sales.

At the same time there is an urgent need for public health research to identify clearly the full range of costs and benefits associated with the widespread use of pesticides. This will allow nations to make policy decisions based on agricultural, environmental, nutritional and health grounds.

(Excerpts from an article by Professor David Gunnell, Professor Ravindra Fernando, Dr. Medhani Hewagama, Dr. W. D. D. Priyangika, Dr. Fleming Konradsen and Dr. Michael Eddleston, published in the International Journal of Epidemiology)

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