-from Epidemiological Bulletin, Vol. 22 No. 4, December 2001-
Introduction
Surveillance in public health requires the systematic and continuous collection,
analysis, and interpretation of data on health events. These data are then used
in the planning, execution and evaluation of health interventions. A surveillance
system requires developing the functional ability to compile, analyze, and disseminate
data in a timely fashion to those able to undertake effective prevention and
control actions.
In public health, it is imperative to direct surveillance actions not only to health problems of infectious or chronic origin, but also those caused by external agents. These agents can be closely related to the environment, which has been deteriorating at an increased pace over the last decades.
In the case of pesticides, the Pan American Health Organization (PAHO) established as a priority promoting better methods for collecting data related to acute pesticide poisoning (APP) in member countries. The aim is to better understand health problems caused by pesticides, the magnitude of which are still not known with precision. This document presents some preliminary guidelines proposed and adopted by PAHO on this subject.
An APP surveillance system makes it possible to determine how poisoning is affecting the population’s health, population groups most affected, types and characteristics of high risk exposures, main pesticides involved, and other determining factors. This information is used to direct prevention and control actions to reduce the negative health effects of chemical substances in places where cases are identified (i.e. in practical terms, an epidemiological blockade).
Furthermore, if surveillance system data are cross-checked with complementary information from other sources, surveillance can facilitate the identification of pesticide use patterns and evaluation of contaminated soils, water and pesticide residues in food.
1. Objectives of the surveillance system
– Determine the number of cases and deaths by APP according to time, place,
and person (in populations and regions of greater risk, with trends over time)
and their principal determining factors, to implement timely prevention and
control measures. This makes it possible to calculate the APP morbidity and
mortality incidence.
– After an outbreak of cases is identified, investigate the origin and develop
training activities aimed at avoiding new cases (epidemiological blockade).
– Define high-risk populations.
– Detect situations of alert where effective and timely actions are required
to minimize the negative public health effects of poisoning.
– Characterize pesticide exposures that pose the greatest risks for the population.
– Determine the causes of poisoning and death in the population.
– Identify pesticides more frequently related to APP.
– Focus the design of prevention and control strategies towards these problems
in the population.
– Facilitate the evaluation of environmental conditions that create risk situations,
in order to propose control measures.
– Direct research proposals to determine the public health implications of pesticide
use and the effectiveness of prevention and control actions.
2. Case Definition
A case of APP is defined as any person who, after having been exposed to one
or more pesticides, presents clinical manifestations of poisoning, or specific
laboratory test results compatible with poisoning, in the first 24 hours after
contact.
Manifestations of the diseases caused by APP are often not very specific. One source of information that contains a list of the most important signs and symptoms is a manual from the United States Environmental Protection Agency (EPA): Recognition and Management of Pesticide Poisonings. Fifth edition, 1999; USA. Click here to access this manual in pdf format.
At the state level in the United States, a monitoring index is used to assign a level of severity to different diseases due to APP. Table 1 shows the signs and symptoms according to severity categories (Click here to access the original table).
Case classification
Suspected Case
A case that suggests acute pesticide poisoning by presenting a symptomatology
compatible with poisoning (systemic or localized) and/or is suspected to have
been exposed to pesticides.
Confirmed Case
A case in which at least one of the following criteria is established:
– Epidemiological visit where the background of exposure to the toxic substance,
the means of exposure, the agent, the mechanism, and their relation in time
are identified and, additionally, presenting clinical manifestations of poisoning.
– History of exposure to the toxic substance and altered biological indicators
of exposure or effect in accordance with the pesticide, and presence or no presence
of clinical manifestations.
– In case of death, confirmation with medical-legal procedures.
According to the circumstance of the exposure:
– Occupational: Exposure to pesticides during the industrial processes
of manufacture, storage, transportation, application, and final disposal.
– Accidental: Unintentional and unexpected exposure to pesticides. This
includes food poisoning.
– Intentional: Exposure to pesticides with the intention of causing harm.
This includes suicide attempts, suicides, and homicides.
According to characteristics of the pesticide:
Chemical Group:
- Bipyridyls
- Carbamates
- Arsenical compounds
- Copper compounds
- Organochlorine compounds
- Organotin compounds
- Organophosphate compounds
- Organomercury compounds
- Derivatives of phenoxyacetic acid
- Coumarins and Indandiones
- Derivatives of hydrocarbons, halocarbons, oxides, and aldehydes, composed
of sulfur, composed of phosphorus, composed of nitrogen (all as fumigants)
- Nitrophenolics and Nitrocresolic
- Pyrethrins and Pyrethroids
- Thio- and dithiocarbamates
- Triazines
- Others
Organisms to control:
- Insecticides
- Herbicides
- Fungicides
- Rodenticides
- Nematicides
- Acaricides
- Bactericides
- Others
Toxicological Classification of Pesticides/WHO *
- Ia: Extremely hazardous
- Ib: Highly hazardous
- II: Moderately hazardous
- III: Slightly hazardous
Definition of Alerts
A set of events related to pesticide poisoning which, according to epidemiological
criteria, demand immediate intervention. They include:
– Death
– Poisoning in pregnant or lactating women
– Poisoning in children (minors as defined by each country legislation)
– Severe poisoning
– Two or more cases in a week, in the same place
– Two or more cases on a given day or cases on consecutive days in the same
place
– Poisoning with unregistered or prohibited pesticides
– Alerts that the local pesticide monitoring commission consider should be investigated
– Emergencies where pesticides are involved such as: leaks, spills, natural
disasters, technological disasters and others
3. Operational organization of the surveillance system
Surveillance Types
Through passive surveillance the background of pesticide exposure is
sought in persons attended by health services personnel who present compatible
signs and symptoms.
Notification of APP cases is made on a periodic basis. Reports are made immediately at the local level, weekly at the national level, and quarterly at the level of international agencies. These reports are integrated into the established notification system within the local public health surveillance system or pesticide prevention and control program when applicable.
In specific cases, surveillance can be carried out to monitor occupational risks with evaluation of environmental conditions and/or utilization of biological markers (active surveillance). Some biological markers can identify early alterations due to pesticide exposure.
In the case of an alert situation as previously defined, notification to the local health authority should be immediate and a compulsory epidemiological investigation should be conducted for every case.
Data collection
Data Sources
Morbidity: APP case notification forms; notifications by Local Pesticides
Commissions; community notifications. If resources are adequate, it is possible
to use registries of medical consultations and emergencies, clinical histories
of patients and hospital discharge information to confirm that there were no
additional cases.
Research findings and laboratory results can be used to actively look for cases of pesticide poisoning in high-risk groups.
Consolidated monthly reports of data summarizing the epidemiological behavior of APP.
Mortality: individual death certificates, hospital or emergency mortality records, vital statistics and community medical and legal records.
Field investigations: reports of epidemiologic field studies carried out due to the presence of alert situations such as poisoning outbreaks or cases of special importance.
Other registries (when resources are available): reports of occupational injuries and labor absenteeism; registries of companies and of the Ministry of Labor; press reports and results of special research, for example on evaluation of underreporting.
Environment: Soil and water monitoring reports and reports of pesticide residues in food. Classification of pesticides used; hygiene and safety conditions and use of personal protection against pesticides.
Minimum data recommended
For each case of APP:
Socio-demographic variables: age, sex, origin (urban / rural), education,
occupation.
Exposure variables: place and activity at time of exposure, date, hour of exposure, means of exposure, cause of the poisoning (occupational, accidental, intentional).
Variables related to the clinical manifestations: date and hour of onset of symptoms, type of clinical manifestations, severity of clinical manifestations, condition of discharged patient (alive / dead).
Variables related to the implicated pesticide(s): type of pesticide, generic name, brand name, classification according to chemical group and according to type of organism controlled; type of crop.
Note: These data are included in the notification form at time of patient admission or subsequently based on clinical history data.
Data consolidated periodically (monthly or yearly):
- Total number of poisonings
- Number of poisonings by sex
- Number of poisonings by 5-year age groups
- Number of poisonings in children (minors as defined by the legislation of
each country)
- Number of poisoning by cause: occupational, accidental, intentional
- Number of deaths from poisoning
- Number of deaths from poisoning by age and sex
- Number of deaths from poisoning in children (minors as defined by the legislation
of each country)
- Number of deaths from poisoning by cause: occupational, accidental, intentional
- Number of occupational poisonings by type of crop
- Total poisonings per month
- Total weight of pesticides imported annually by country (in kg): by chemical
group, type of organism to control and by toxicological classification
- Number and type of alert situations
- Number and type of prevention and control measures carried out (inspection
visits, active search of new cases, hygiene and safety conditions improvement,
education, compliance with legislation, follow-up of previous activities, others)
- Cases by place of occurrence (company, neighborhood, city)
Instrument
The form for Report of Acute Pesticide Poisoning should be used for every person
that is attended by health services, or who dies and meets the criteria established
in the Case Definition.
Additional sources
The following information will be needed to analyze the data provided by
the surveillance system.
- Socio-demographic information (total population, population of economically
active age, proportion of economically active population working in agriculture,
distribution of the population by age and sex, by urban/ rural origin and by
level (local, regional or national).
- Imports of pesticides by chemical group, by type of organism to control, and
according to toxicological classification.
- Types, areas, and seasons of crops. Technologies used for these crops.
- Pesticide waste inventory.
- Monitoring of pesticide residues in food.
- Environmental impact assessments. Contamination of water and soil.
- Census of job sites by Municipality.
- Directory of organizations and institutions which work with pesticides that
may have resources available.
- Available legal framework (laws, regulations, technical standards)
- Laboratory capacity at local and national level.
- Investigations and studies in the area.
4. Data analysis
Epidemiological Indicators
Incidence rate of acute poisoning: Number of new cases of APP in a period
/ Population at mid- period x 100,000
Mortality from acute poisoning: Number of deaths by APP in a period / Population at mid- period x 100,000
Case-fatality: Number of deaths by APP in a period / Number of cases of APP in a period x 100
Rate or in case of not having data for denominators, proportional
distributions:
Proportion of cases by sex
Proportion of cases by age group
Proportion of cases in children (minors as defined by each country legislation)
Proportion of cases according to type of pesticide (chemical group, organism
to control and WHO toxicological classification)
Proportion of cases according to cause of poisoning (occupational, accidental,
intentional)
Proportion of cases of occupational poisoning by type of agriculture
Proportion of cases by place or company
Indicators regarding the importation of pesticides
– Kilograms of Imported Active Ingredients* / Number of inhabitants in the country
– Kilograms of Imported Active Ingredients* / Population economically active
in agriculture.
– Kilograms of Imported Active Ingredients* / Hectares cultivated
In the analysis of these epidemiological indicators, monthly or yearly trends can be calculated. These trends can be analyzed for different localities, regions or countries. Behavior by sex, age group, cause of poisoning, type of pesticide according to chemical group, and type of organism to control also can be analyzed in time. To present this information, trend graphs are used to illustrate rates and pie or bar graphs to represent the proportional distributions of the proposed variables. Maps are also useful to geographically locate where cases occur and define high-risk areas in a locality.
5. Dissemination of Information
It is of vital importance that information from a surveillance system reach
the people and institutions responsible for decision-making in a timely fashion.
With this information, decision-makers will be able to effectively direct timely
prevention and control actions. In situations where APP is involved, information
needs to be shared not only among health authorities but other organizations
as well. These situations require the involvement and commitment of regulatory
agencies, occupational health programs, local pesticide commissions, and the
community. Dissemination of information can be carried out through bulletins
which include epidemiological analysis of APP using proposed indicators. Also,
the mass media can be used to strengthen education related to the proper use
of pesticides.
Uses of data for decision-making
Surveillance:
- Analyze the epidemiological behavior of APP and related mortality.
- Estimate the magnitude of the problem by using incidence rates of APP and
mortality in the population, by locality and year.
- Monitor the characteristics of APP cases and deaths by sex, age, and specifically
in children, using incidence and mortality rates.
- Characterize APP according to cause (occupational, accidental, intentional)
through proportional distributions of cases by place and year.
- Describe the pesticides responsible for APP cases and deaths through a classification
list according to chemical group, organism to control, and toxicological classification.
- Identify and characterize alert situations according to year, place, source
of poisoning, type of pesticide, number of affected people, number of deaths,
cause, and prevention and control actions.
Investigation:
- Characterize the changes in APP frequency by time and place
- Identify populations at risk through periodic monitoring
- Characterize importation and utilization of pesticides in different places
- Identify the impact of specific pesticides on public health for the purpose
of regulating their use
- Develop and strengthen enforcement of legislation in the area
- Provide impetus for organized education and control activities regarding the
use of Pesticides
- Assess the impact of different intervention strategies for the problem of
APP.
- Monitor soil, water, and work places, as well as pesticide residues in food.
- Characterize under-registration, using a standard model
6. Evaluation of the System
To evaluate the fulfillment of APP surveillance activities, an assessment must
be carried out at every participating level: local, regional, and national.
Evaluation includes: 1) fulfillment of the directives established by the system,
2) administrative and human resources, including appropriate materials for the
development of the system and resources necessary to carry out activities of
surveillance, 3) Aspects related to the system’s capacity to detect cases and
prevent and control future cases, 4) Reduction of morbidity and mortality rates.
Indicators of fulfillment of surveillance actions
– Proportion of reported cases with complete report file
– Proportion of cases reported by the community
– Proportion of alert situations that are investigated
– Proportion of alert situations with intervention follow-up in occupational
and accidental cases
– Time elapsed between reported and investigated cases.
Attributes of the system:
It is considered a prerequisite that data available through the surveillance
system are of good quality and consistent. The system must also be sustainable
and stable.
Simplicity: Ease of collection and analysis of APP data.
Flexibility: Capacity to incorporate monitoring of the APP in existing surveillance
systems.
Acceptability: Willingness of individuals and organizations to participate in
the Surveillance System.
Sensitivity: Ability of the system to capture the cases of APP that really occur
in the population. It can be affected by underreporting and low quality of the
diagnosis.
Positive predictive value: Proportion of APP cases captured by the system that
really are cases.
Representativeness: Capacity of the system to accurately reflect APP that occur
at territorial levels. It can also be affected by underreporting.
Opportunity: Rapid availability of the APP data for its report and response.
7. Responsibilities of the Surveillance System at different
levels.
Local level:
– Data collection
– Alert identification
– Epidemiological investigation of the alerts
– Epidemiological analysis
– Prevention and control actions
– Report to higher levels
– Dissemination of pertinent information
Regional level:
– Consolidation of information from local levels
– Epidemiological analysis of behavior of the problem in the region
– Report to the national level
– Advisory services at the local levels
– Dissemination of information at regional and local levels
– Evaluation of the System at the local level
National level:
– Consolidation of information from the regional levels
– Epidemiological analysis of the behavior of the problem at the national level
– Advisory services at regional levels
– Strengthening of sanitary regulation regarding pesticides
– Evaluation of the Surveillance System at the regional level
– Dissemination of information at the national, regional and local levels
References:
(1) Belize. Ministry of Health. Manual for de Epidemiological Surveillance of
Acute Pesticide Intoxication in Belize. Belize, 2000, pp-20.
(2) Brazil, Ministério da Saúde. Manual de Vigilancia da saúde de populacoes
expostas a agrotóxicos. Divisao de Meio Ambiente e ecología Humana. Organizacao
Pan-Americana da Saúde, Brasilia, 1997.
(3) Centers for Disease Control and Prevention. Updated Guidelines for Evaluating
Public Health Surveillance Systems. MMWR. July 27, 2001; 50 (No. RR-13):1-35.
(4) Costa Rica, Ministerio de Salud, Caja Costarricense de Seguro Social, Instituto
Nacional de Seguros. Protocolo de Vigilancia Epidemiológica para el manejo de
las intoxicaciones causadas por plaguicidas. San José de Costa Rica, 2001. pp.
1-28.
(5) Chile, Ministerio de Salud. Red Nacional de Vigilancia Epidemiológica de
Plaguicidas. Situación epidemiológica de las intoxicaciones agudas por plaguicidas.
Chile, 1998. Santiago de Chile, 2000 pp. 1-45.
(6) Environmental Protection Agency (EPA) Recognition and Management of Pesticide
Poisonings. Fifth edition. Washington, 1999; pp.236
(7) Guatemala, Ministerio de Salud Pública y Asistencia Social. Instituto Guatemalteco
de Seguridad Social. Manual para la Vigilancia Epidemiológica de Intoxicaciones
por plaguicidas. Guatemala, 1998; pp. 30.
(8) Honduras. Secretaría de Salud Pública. Manual para el Abordaje Integral
de las Intoxicaciones Agudas por Plaguicidas. Tegucigalpa, 2000; pp. 71.
(9) IPSC. International Programme on Chemical Safety. The WHO Recommended Classification
of Pesticides by Hazard and Guidelines to Classification 2000-2002. Geneva,
2001.
(10) Nicaragua. Ministerio de Salud. Dirección General de Salud y Epidemiología.
Manual de Vigilancia Epidemiológica. Managua, 2000; pp. 50.
(11) Panamá, Ministerio de Salud. Normas de Vigilancia Epidemiológica de las
Intoxicaciones Agudas por plaguicidas. Panamá, 1999.
(12) PLAGSALUD/OPS. Informe 2000. Vigilancia Epidemiológica de Intoxicaciones
Agudas por Plaguicidas. San José, 2001; pp.29-36.
(13) República de El Salvador. Ministerio de Salud Pública y Asistencia Social.
Normas y procedimientos para la vigilancia epidemiológica de las intoxicaciones
agudas y crónicas por plaguicidas. El Salvador, 1998.
(14) Teutsch, SM., Thacker, SB. Planificación de un sistema de vigilancia en
salud pública. Boletín Epidemiológico. Organización Panamericana de la salud.
1995; 16(1):1-7.
(15) World Health Organization, International Labour Organization, United Nations
Environment Programme. Epidemiology of pesticide poisoning. Harmonized collection
of data on human pesticide exposures in selected countries of the western pacific
region. International programme on chemical safety. Geneva, 2000.
Source: Prepared by Dr. Samuel Henao from the PAHO/WHO Representation in Costa Rica and Dr. Maria Patricia Arbelaez from the Public Health Department of the University of Antioquia, Medellin, Colombia.
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Epidemiological Bulletin, Vol. 22 No. 4, December
2001