– June 2003:
Variations in the Use
of, and Exposure to
Pesticides among Hmong Farmers in Northern
talk by Dr. Peter Kunstadter
Present: Sean Ashley,
Hans-Dieter Bechstedt, Parinya
Bhanuwase, John Cadet, Jim Campion, Ken Dyer, Roy
Hudson, Jack Kelly, Marc, Sophie
and David Lallemant, Patcharin Nawichai, John C. Quicker, Lamar and
Robert, Carina zur Strassen, Caroline Subkaen, Jessica Wilson. An
Peter’s talk was compiled by your
convenor from the handout that Peter had prepared for
Since the 1970s, Hmong farmers
have changed from ‘organic’
subsistence shifting cultivation to fixed-field cash crop farming using
This paper considers some of the
behavioural and biomedical
consequences of the shift from land-extensive, labour-intensive
subsistence production for home use, to land- chemical- and
fixed-field farming of cash crops for lowland and international
Hmong community selected for study is about 30 km from Chiang Mai.
concentrate on the production of lichee fruit, most of which is sold to
merchants and canneries, which entails the seasonal use of many
chemicals including pesticides.
We report results of behavioral
surveys in April 2002, and
blood tests in April 2002 (peak of pesticide use), October 2002 (end of
pesticide use), and January 2003 (3+ months without pesticide use) to
seasonal changes in use of, and exposure to pesticides in a random
sample of 26
Hmong households (232 individuals from 1 year old to as old as they
discuss culturally appropriate options to reduce expose.
The question to be asked before
we go any further is, ‘Why
are the Hmong farmers using pesticides?’ The answer to that is to
be found in
Tradition and Change
Hmong farmers were traditionally
using a land-extensive,
labour-intensive long cultivation-long fallow system of shifting
slash and burn.
Their major subsistence crops
were upland (dry) rice and
maize, and their major cash crop was opium.
Starting in the mid-1960s, the
Royal Thai Government, with
international (UN) and bilateral (US and other Western countries)
introduced ‘crop substitution’ of non-narcotic cash crops
to reduce opium
cultivation as one initial step in the total eradication of the sale
and use of
In the mid-1980s, after the
construction of an extensive
highland road network, the Royal Thai Government changed its highland
development policies and began serious efforts to destroy opium crops
arrest opium producers, stop shifting cultivation and prevent access to
highland areas defined to belong to the Royal Forest,
and restrict movement out of and between existing villages. Stopping
cultivation and preventing access to highland areas effectively reduced
area of land available for cultivation by up to 90% for some farmers.
success of this new policy quickly destroyed the traditional Hmong
Responses to Change
In response to these changes,
the Hmong highlanders were
forced to change. In response to their perception of land shortages
rapidly reduced desired family size and cut birth rates by using modern
planning methods. They increased enrollment of their children in
has resulted in an increase in perceived costs and a decline in the
economic value of their children. They have adopted a large variety of
crops that require the intensive application of chemicals (Hmong
our sample reported using 70 different kinds of chemical in the 12
before April 2002. These chemicals included fertilizers, herbicides,
insecticides, fungicides, hormones, and adherents.) plus the use of
machinery (small ploughs, sprinkler irrigation, chemical spray pumps),
which had been used traditionally.
Materials and Methodology
We interviewed all household
members over 15 years of age to
regarding – demographic and socioeconomic characteristics, their
use of and
potential exposure to pesticides, their use of measures to prevent or
exposure, and the prevalence of symptoms associated with exposure to
We screened for cholinesterase
inhibition using rapid
(treated paper) test of finger-stick blood from all participating
members over one year old.
We examined venous blood for
chromosomal aberrations from 2
adults in each household.
A summary of the results
In the screened population of
sample households there were
102 males / 105 females.
Education is strongly associated
with age and gender. Most
children of both sexes are currently enrolled in school. Adults aged
more education than older adults. Males over 20 years old have more
Thai language ability is
associated with age and gender, and
the distribution is similar to that of education.
The religion of this community
is about one-third animist,
one-third animist + Buddhist, and one-third Christian.
Occupation – Most adults
are farmers. The highest percentage
is in the 20-39 age group, with a ratio by gender of 87% male to 96%
Beliefs about pesticides
Benefits – The major
benefits perceived from the use of
pesticides are the improvement of crops and the killing of insects,
pests and diseases.
Negative effects – The
major negative effects perceived by
our sample are physical illness and harm to the environment.
When asked in more detail about
the perceived effects of
pesticides on their health, 31% of male and 24% of female respondents
experience of specific symptoms – headaches, dizziness, blurred
tingling limbs, numb hands and feet, vomiting, itchiness, skin sores
allergies. They are also concerned that pesticides can cause not only
but also disability and death.
The major effects on
children’s health perceived by our
respondents are illness and death. Children’s illnesses specified
respondents are – Will not grow or develop normally,
crippled, blind, dizzy, brain damage, decreased immunity, difficult
vomiting, fever, headaches, weak, blurred vision, and yellow and pale
Methods of Application of Pesticides
The usual method of application
of chemicals is by machine
spray, with fertilizers broadcast by hand. Respondents reported that
chemicals are applied, that is actually holding the spray gun, much
by men than by women, ignoring the fact, however, that women usually
hose from the machine-powered pump while men are doing the spraying.
Screening for Cholinesterase
None of the villagers of all
ages and both sexes who were
screened had ‘normal’ levels of cholinesterase inhibition
and a large
proportion had ‘risky’ or ‘dangerous’ levels.
Male/female differences (higher
proportion of males with
‘risky’ or ‘dangerous’ levels) are significant
for ages 10-19 (p = 0.04) and
20-39 (p = 0.02).
Symptoms associated with Pesticide
A substantial proportion of
respondents reported symptoms
‘sometimes’, ‘often’ and ‘every
time’ after pesticide applications. Reported
symptoms included – headache, dizziness, blurred vision, numb or
and feet, itching, nausea, and vomiting.
Behaviour and Exposure to Pesticides
Protective measures to reduce
exposure to pesticides include
– wearing a mask, gloves, boots and waterproof or heavy clothing,
out of a field after application. A large proportion of individuals,
children, do not use protective clothing or any other methods to
exposure to pesticides.
The results of screening showed
that adults who use masks
only ‘sometimes’ or ‘never’ are twice as likely
to have ‘dangerous’ levels of
cholinesterase inhibition as those who use masks ‘always’
or ‘most of the time’.
Also that a much higher proportion of men and women who have
‘safe’ levels of cholinesterase inhibition do not wear
In reality, as a result of the
land-use policies imposed
upon them by the Thai Government, 100% of the villagers are exposed to
pesticides. Their homes are now cheek by jowl with the orchards and
and even when their land is at a distance away from the village,
in field huts during the spraying months. The powerful machine pumps
to apply the chemicals atomize the pesticides into a chemical-laden
shrouds the whole area, until the wind carries it on to the next
town, or city.
The widespread use of pesticides
and other farm chemicals is
associated with perceived benefits to improve crop yield and price and
insects, and to speed work and decrease labour.
Most villagers are aware of
risks associated with the use of
pesticides. These risks include health risks, both to themselves and
children, and risks to the environment.
Screening for exposure to
organophosphate pesticides by
testing for cholinesterase inhibition at the season of maximum use of
pesticides shows high levels of exposure both among those people who
pesticides and those who do not, and that the highest proportion of the
population at ‘dangerous’ levels are among young children
and males and females
of reproductive age.
Screening during seasons of low
use and no use showed a
decline in levels of cholinesterase inhibition.
Adults in the study population
show a larger number of
chromosomal anomalies than in a control population. The meaning of
results is, however, not yet clear.
Villagers are aware of the risks
and do use various methods
to reduce exposure. These methods include the safe storage of
wearing protective clothing.
The use of protective clothing
is more common and more
consistent for men than women.
Adults who report wearing masks
and/or gloves ‘sometimes’ or
‘never’ while applying pesticides are more likely to have
than those who wear them ‘always’ or ‘most of the
There is no relationship between
the level of cholinesterase
inhibition and other protective measures – wearing boots, heavy
clothing and staying out of fields after application of pesticides.
Into the future
We are discussing possible
interventions with villagers to
reduce their exposure. Methods to reduce exposure and constraints of
the use of
pesticides being suggested to villagers are:
Always wear a full set of
protective clothing when applying
pesticides. Villager’s response to this is that protective
clothing is hot,
extremely uncomfortable and makes it hard to move up and down hills and
Reduce or stop using pesticides
altogether. Their response
to this is that pesticides are necessary to insure quality, yield and a
price for the product.
Keep all children out of fields
at all times. This is not
practical because of the need for breast-feeding mothers and older
labour in the fields.
Restrict pesticide application
to one area in one day. Two
reasons why this is not practical. Firstly because some households have
orchards in different areas and its not practical to spray on different
Secondly because some farmers sell their crop to brokers when trees are
bloom in January. Brokers have their own spray teams and schedules,
farmers have no control.
Our sample population is heavily
exposed to pesticides.
The use of pesticides is driven
largely by economics.
We are continuing in discussions
with villagers to find a
method of decreasing exposure that is effective, economically and
environmentally feasible and locally acceptable.
Market forces, including
increased production and falling
prices of lichees, are already making villagers consider other crops.
Selection of the appropriate
combination of crops and
cultivation methods is complicated by annual variations in crop yields
prices and the rapid responses of farmers throughout Thailand
to market conditions.
The Hmong farmers have been
forced, by external agents,
between a rock and a hard place. There are very few, if any,
to them which do not include the inevitable extinction of their culture.
In answers to
questions from the
audience, Peter explained
that pesticides are nerve agents, exactly the same as nerve gases,
insects by disrupting the chemical transmitters in their nervous
same chemical transmitters are found in the nervous systems of all
including homo sapiens.
Pesticides are used worldwide.
They are dangerous and, in
Western countries, their use is subject to strict regulations. The
exacerbated in Thailand
firstly because there is no effective system of regulation in force to
and monitor farmers. Unfortunately most farmers here work on the
if some is good then more is better. And secondly because Western
companies dump chemicals in third world countries that they are
selling in the West.
Should the ‘outside
world’ be concerned about the plight of
Hmong farmers? Yes, there is one good, selfish, reason why they must
instructions on the side of the pesticide container say stop spraying
two weeks before harvesting. Traders, who buy a crop while it is still
tree, will continue spraying up to the day of harvesting. Unless the
completely removed it will stay on the fruit and into the can. On a
canned lichees that we bought locally, the labels were written in Thai,
English, Japanese and Chinese.
question and answer
session, the meeting adjourned
to the Alliance Cafeteria where members of the audience engaged Peter
informal discuss over drinks and snacks.