Differences between organophosphates in respiratory failure and lethality with poisoning post the 2011 bans in Sri Lanka

Restrictions on Pesticides and Deliberate Self-Poisoning in Sri Lanka

Importance

Deliberate self-poisoning using pesticides as a means of suicide is an important public health problem in low- and middle-income countries. Three highly toxic pesticides-dimethoate, fenthion, and paraquat-were removed from the market in Sri Lanka between 2008 and 2011. In 2015, less toxic pesticides (chlorpyrifos, glyphosate, carbofuran, and carbaryl) were restricted. Subsequent outcomes have not been well described.

Objective

To explore the association of pesticide bans with pesticide self-poisonings and in-hospital deaths.

Design, Setting, and Participants

In this cross-sectional study with an interrupted time series design, data were prospectively collected on all patients with deliberate self-poisonings presenting to 10 Sri Lankan hospitals between March 31, 2002, and December 31, 2019, and analyzed by aggregated types of poisoning. The correlates of pesticide bans were estimated within the pesticide group and on self-poisonings within other substance groups. The data analysis was performed between April 1, 2002, and December 31, 2019.

Exposures

Implementation of 2 sets of pesticide bans.

Main Outcomes and Measures

The main outcomes were changes in hospital presentations and in-hospital deaths related to pesticide self-poisoning as measured using segmented Poisson regression.

Results

A total of 79 780 patients (median [IQR] age, 24 [18-34] years; 50.1% male) with self-poisoning from all causes were admitted to the study hospitals, with 29 389 poisonings (36.8%) due to pesticides. A total of 2859 patients died, 2084 (72.9%) of whom had ingested a pesticide. The first restrictions that targeted acutely toxic, highly hazardous pesticides were associated with an abrupt and sustained decline of the proportion of poisonings with pesticides (rate ratio [RR], 0.85; 95% CI, 0.78-0.92) over the study period and increases in poisonings with medications (RR, 1.11; 95% CI, 1.02-1.21) and household and industrial chemicals (RR, 1.20; 95% CI, 1.05-1.36). The overall case fatality of pesticides significantly decreased (RR, 0.33; 95% CI, 0.26-0.42) following the implementation of the 2008 to 2011 restrictions of highly hazardous pesticides. Following the 2015 restrictions of low-toxicity pesticides, hospitalizations were unchanged, and the number of deaths increased (RR, 1.98; 95% CI, 1.39-2.83).

Conclusions and Relevance

These findings support the restriction of acutely toxic pesticides in resource-poor countries to help reduce hospitalization for and deaths from deliberate self-poisonings and caution against arbitrary bans of less toxic pesticides while more toxic pesticides remain available.

The Associations between Organophosphate Pesticides (OPs) and Respiratory Disease, Diabetes Mellitus, and Cardiovascular Disease: A Review and Meta-Analysis of Observational Studies

Although some epidemiological studies have identified the associations between exposure to organophosphate pesticides (Ops) and respiratory diseases, diabetes mellitus (DM), and cardiovascular diseases (CVDs), controversial results still exist. In this review and meta-analysis, we aimed to investigate the overall pooled effect estimates and the possible mechanisms of the relationship between OP exposure and adverse health outcomes. In this study, Web of Science, PubMed, Embase, OVID, and the Cochrane Library were systematically searched until September 2022. Nineteen observational studies that focused on the general population or occupational populations examined the associations between OP exposure and respiratory diseases, DM, and CVD were included. Based on the overall pooled results, a significantly positive association was observed between OP exposure and respiratory diseases (OR: 1.12, 95% CI: 1.06-1.19). A significant link was also observed between various individual species of OP exposure and respiratory diseases, with an OR value of 1.11 (95% CI: 1.05-1.18). In particular, there was a significant association of OPs with wheezing and asthma, with OR values of 1.19 (95% CI: 1.08-1.31) and 1.13 (95% CI: 1.05-1.22), respectively. In addition, a significant association was also observed between OP exposure and DM (OR: 1.18, 95% CI: 1.07-1.29). However, no significant association was observed between OP exposure and CVD (OR: 1.00, 95% CI: 0.94-1.05). Exposure to OPs was associated with a significantly increased risk of respiratory diseases and DM, but there was no evidence of a significant association between OP exposure and CVD. Considering the moderate strength of the results, further evidence is needed to confirm these associations.

Alcohol use, self-harm and suicide: a scoping review of its portrayal in the Sri Lankan literature

Background

Suicide is a global public health problem. Compared to other middle-income countries, much literature has been generated on the topic of self-harm and suicide in Sri Lanka. Harmful use of alcohol is a well-known risk factor to self-harm and suicide, however the connection needed further exploration.

Aim

The aim was to investigate alcohol's role in self-harm and suicide in Sri Lanka to inform policy and prevention programs and future research priorities.

Methods

We performed a scoping review exploring how the association between alcohol use, self-harm and suicide in Sri Lanka is presented in scientific literature from August 1, 2008 to December 31, 2022. Thematic analysis was used to explore emerging themes.

Results

Altogether 116 peer-reviewed articles were included. Three themes emerged: (i) gendered, inter-relational explanations of alcohol's role in self-harm, (ii) hospital management of patients who co-ingested alcohol and pesticides, and (iii) proposed research and interventions targeting alcohol, self-harm and suicide. The articles' recommendations for policy, prevention and research priorities included: Family- and community-based alcohol, self-harm and suicide reduction interventions; viewing self-harm as a window of opportunity for health personnel to intervene in families affected by harmful alcohol consumption; and introduction of and increased access to treatment of alcohol use disorder at the individual level.

Conclusion

Suggestions for alcohol, self-harm, and suicide prevention interventions were primarily targeted at the community, though this might also reflect the limited treatment, mental health, and alcohol support available in the country. Future research should explore and test context-appropriate interventions integrating alcohol and self-harm prevention and treatment.

Lung injury caused by aspiration of organophosphorus insecticide and gastric contents in pigs

INTRODUCTION

Patients who require mechanical ventilation after self-poisoning with ingested organophosphorus (OP) insecticides often die. Aspiration of stomach contents may contribute to lung injury and lethality. This study was designed to assess the severity of direct and indirect pulmonary injury created by pulmonary instillation of mixtures of OP insecticide, solvent (Solv) and porcine gastric juice (GJ) compared to controls.

METHODS

Terminally anaesthetised minipigs (groups n = 5) were exposed to sham bronchoscopy or given mixtures (0.5 mL/kg) of: saline, GJ, OP insecticide and GJ (OP + GJ), or Solv and GJ (Solv + GJ), placed into the right lung, and monitored for 48 h. Lung injury was assessed through analysis of bronchoalveolar lavage fluid (BALF), computed tomography and histopathology.

RESULTS

OP + GJ created a direct lung injury consisting of neutrophil infiltration, oedema and haemorrhage, as well as indirect injury to the other lung. OP + GJ directly-injured lung parenchyma had increased concentrations of BALF protein, albumin, IL-6, IL-8 and C-reactive protein (CRP) at 24 h (p < 0.05), and BALF protein, albumin and CRP at 48 h (p < 0.05), when compared with controls. Aspiration of GJ produced similar direct effects to OP + GJ but less indirect lung injury. Lung injury was less severe after Solv + GJ, for combined lung histopathology scores (vs. OP + GJ, p < 0.05) and for the proportion of directly-injured lung that was poorly/non-aerated at 48 h.

CONCLUSION

Pulmonary instillation of OP + GJ created more lung damage than controls or Solv + GJ. In patients with severe OP insecticide poisoning and reduced consciousness, early airway protection is likely to reduce pulmonary damage.

Organophosphate pesticides sequestered in tissues of a seagrass species - Zostera capensis from a polluted watershed

Organophosphate pesticides (OPPs) are persistent in the environment, but little information is available on their bioaccumulation in seagrass. In this study, the seagrass - Zostera capensis was collected from Swartkops Estuary in South Africa to investigate the bioaccumulation of OPPs from contaminated sediments and the water column. This plant was chosen because it grows abundantly in the estuary's intertidal zone, making it a viable phytoremediator in the urban environment. Extraction was performed by the QuEChERS method followed by GC-MS analysis. The mean concentration of ∑OPPs ranged from 0.01 to 0.03 μg/L for surface water; 6.20-13.35 μg/kg dw for deep-rooted sediments; 18.79-37.75 μg/kg dw for leaf tissues and 12.14-39.80 μg/kg dw for root tissues of Z. capensis. The biota-sediment accumulation factors (BSAFs) were greater than one, indicating the potential for Z. capensis to bioaccumulate and intercept the targeted pesticides. A weak insignificant correlation observed between log BSAFs and log Kow indicates that the bioaccumulation of OPPs in tissues of Z. capensis were not dependent on the Kow. Eight of the selected pesticides had root-leaf translocation factors (TFr-l) greater than 1, indicating that Z. capensis can transport these chemicals from roots to leaves. The results from this study implies that this plant species can clean up OPP contamination in the environment.

Case fatality of agricultural pesticides after self-poisoning in Sri Lanka: a prospective cohort study

BACKGROUND

Pesticide poisoning is among the most common means of suicide globally, but can be prevented with regulation of the most hazardous agents. We aimed to compare the lethality of pesticides ingested by our cohort, seek evidence on variation between human and regulatory animal toxicity, and establish change over time in the case fatality of individual pesticides in Sri Lanka.

METHODS

We examined the case fatality of agricultural pesticides in a prospective cohort in nine hospitals serving rural populations in Sri Lanka. We included all patients (>11 years) who had presented to a South Asian Clinical Toxicology Research Collaboration study hospital during the study period. Patients were enrolled by clinical research assistants and were regularly reviewed. Identification of the ingested pesticide was generally on the basis of history or positive identification of the container, supported by nested blood analysis.

FINDINGS

From March 31, 2002, to Dec 31, 2019, 34 902 patients (median age 29 years [IQR 21-40]; 23 060 [66·1%] male) presented with a possible or known pesticide self-poisoning. We identified 23 139 specific pesticides that were ingested. Poisoning was fatal in 2299 (6·6%) patients. Case fatality varied greatly from 0·0% (several substances) to 41·8% (paraquat). The three most toxic agents (ie, paraquat, dimethoate, and fenthion) were banned between 2008 and 2011. Since 2013, the five agents causing the most deaths (ie, profenofos, propanil, fenobucarb, carbosulfan, and quinalphos) had a case fatality of 7·2-8·6%. A steady decline was seen in overall case fatality of pesticide poisoning (10·5% for 2002-06 to 3·7% for 2013-19), largely attributable to pesticide bans. A modest fall in case fatality for non-banned pesticides was also seen.

INTERPRETATION

Declines seen in case fatalities of poisonings with non-banned pesticides suggest that medical management improved over time. The human data for acute toxicity of pesticides should drive hazard classifications and regulation. We believe that a global benchmark for registration of pesticides should include a less than 5% case fatality after self-poisoning, which could prevent many deaths and have a substantial effect on global suicide rates.

FUNDING

The Wellcome Trust and the National Health and Medical Research Council of Australia.

TRANSLATIONS

For the Sinhala and Tamil translations of the abstract see Supplementary Materials section.

Clinical characteristics and treatment of mixed-pesticide poisoning in a patient: reflections on a particular case

Patients who commit suicide often deliberately hide their medical history. Given that taking pesticides is one of the most common methods of suicide, other forms of poisoning may be neglected in clinical practice. We report here a case of mixed-pesticide poisoning. The patient was poisoned by oral administration of a coumarin rodenticide in combination with an intramuscular injection of organophosphorus (OP) pesticide. The patient was treated with vitamin K1, cholinesterase reactivators, atropine, ventilator-assisted ventilation, and bedside debridement. Her condition gradually stabilized and she eventually recovered and was discharged. Assessment of the causes of delayed diagnosis and treatment suggests that we need to improve early detection and treatment of acute poisoning. It is especially important to ask about the patient’s medical history, conduct a careful physical examination, and track the clinical symptoms and differential diagnosis of common poisoning. In addition to the three common routes of poisoning—oral, inhalation, and cutaneous mucosal contact—intramuscular injection of OP can also lead to severe poisoning, which manifests as respiratory failure.

Acute phenthoate self-poisoning: a prospective case series

BACKGROUND

The clinical characteristics following self-poisoning with organophosphorus (OP) insecticides differs according to the insecticide ingested. Phenthoate is a dimethoxy WHO Hazard Class II OP pesticide with limited literature on its clinical characteristics and outcome. We aimed to better understand its clinical characteristics by studying patients with phenthoate self-poisoning in Sri Lanka.

METHODS

We conducted a prospective cohort study of patients presenting with phenthoate self-poisoning to eight hospitals in Sri Lanka between 2002 and 2018. Clinical outcomes were recorded for each patient. Blood samples for measuring plasma phenthoate concentration, cholinesterase activity, and response to oximes were available for a very small number of patients recruited to a clinical trial.

RESULTS

Two hundred and ninety-two patients who ingested agricultural phenthoate formulations were included in the study. Median time to admission was 3.9 (IQR 2.4 - 6.8) h. Forty-two (14.4%) patients were intubated, mostly (30/37, 81%) within 24 h of ingestion (median time to intubation 7.2 [IQR 2.6-20.9] h). Median duration of intubation was 74.8 (IQR 26.8-232.5) h; the longest duration in a survivor was 592 h. Nineteen died (case fatality 6.5%, 95% CI 4.0-10.0); median time to death was 37 (IQR 16 - 101.7) h. Median plasma phenthoate concentration in patients with samples (n = 81) was 135 (IQR 62.7-356.5) ng/mL (0.42 µmol/mL [0.2 to 1.1 µmol/mL]). Five of six patients receiving pralidoxime chloride 2 g showed an initial increase in AChE and BuChE activity that was not sustained despite an infusion of pralidoxime.

CONCLUSION

Phenthoate self-poisoning has a 6.5% case fatality rate. Most patients who experience respiratory failure undergo early intubation; most deaths occurred among those patients who were intubated less than 24 h after ingestion. There was a non-sustained increase in cholinesterase activity with pralidoxime, but further studies are required to analyse the extent to which oximes are clinically effective in phenthoate self-poisoning.

Development of a histopathology scoring system for the pulmonary complications of organophosphorus insecticide poisoning in a pig model

Organophosphorus (OP) insecticide self-poisoning causes over 100,000 global deaths annually. Around a third of patients are intubated and up to half of these can die. Post-mortem analysis of OP poisoned patients’ lungs reveals consolidation, edema and hemorrhage, suggesting that direct or indirect lung damage may contribute to mortality. The lung injury caused by these formulated agricultural preparations is poorly characterised in humans, and a valid histopathology scoring system is needed in a relevant animal model to further investigate the disease and potential treatments. We conducted two pilot studies in anesthetized minipigs, which are commonly used for toxicological studies. In the first, pigs were given 2.5 mL/kg of either OP (n = 4) or saline (n = 2) by gavage and compared with positive controls (iv oleic acid n = 2). The second study simulated ingestion followed by gastric content aspiration: mixtures of OP (n = 3) or saline (n = 2) (0.63–0.71mL/kg) were placed in the stomach, and then small volumes of the gastric content were placed in the lung. At post-mortem examination, lungs were removed and inflation-fixed with 10% neutral buffered formalin. Samples (n = 62) were taken from cranial and caudal regions of both lungs. Two experienced lung histopathologists separately scored these samples using 8 proposed features of damage and their scores related (Kendall rank order). Two elements had small and inconsistent scores. When these were removed, the correlation increased from 0.74 to 0.78. Eight months later, a subset of samples (n = 35) was re-scored using the modified system by one of the previous histopathologists, with a correlation of 0.88. We have developed a reproducible pulmonary histopathology scoring system for OP poisoning in pigs which will assist future toxicological research and improve understanding and treatment of human OP poisoning.

Emerging pesticides responsible for suicide in rural Sri Lanka following the 2008-2014 pesticide bans

Background

Sri Lanka has reduced its overall suicide rate by 70% over the last two decades through means restriction, through a series of government regulations and bans removing highly hazardous pesticides from agriculture. We aimed to identify the key pesticide(s) now responsible for suicides in rural Sri Lanka to provide data for further pesticide regulation.

Methods

We performed a secondary analysis of data collected prospectively during a cluster randomized controlled trial in the Anuradhapura district of Sri Lanka from 2011 to 16. The identity of pesticides responsible for suicides were sought from medical or judicial medical notes, coroners’ records, and the person’s family. Trend analysis was done using a regression analysis with curve estimation to identify relative importance of key pesticides.

Results

We identified 337 suicidal deaths. Among them, the majority 193 (57.3%) were due to ingestion of pesticides while 82 (24.3%) were due to hanging. A specific pesticide was identified in 105 (54.4%) of the pesticide suicides. Ingestion of carbosulfan or profenofos was responsible for 59 (56.2%) of the suicides with a known pesticide and 17.5% of all suicides. The increasing trend of suicides due to carbosulfan and profenofos over time was statistically significant (R square 0.846, F 16.541, p 0.027).

Conclusion

Ingestion of pesticides remains the most important means of suicides in rural Sri Lanka. The pesticides that were once responsible for most pesticide suicides have now been replaced by carbosulfan and profenofos. Their regulation and replacement in agriculture with less hazardous pesticides will further reduce the incidence of both pesticide and overall suicides in rural Sri Lanka.