PESTICIDE EXPOSURE OF ETHNIC MINORITY HMONG FARMERS IN NORTH THAILAND

1
PESTICIDE EXPOSURE OF ETHNIC MINORITY HMONG
FARMERS IN NORTH THAILAND

• PETER KUNSTADTER, PhD
• UNIVERSITY OF CALIFORNIA SAN FRANCISCO
• UCSF-Fresno Medical Education Program, Asian
  Health Program
• ltarttown_at_itsa.ucsf.edugt
• TIPPAWAN PRAPAMONTOL, PhD
• CHIANG MAI UNIVERSITY
• Research Institute for Health Sciences
• ltrhxxo005_at_chiangmai.ac.thgt
• Paper prepared for meeting of the Society for
  Occupational and Environmental Health, Bethesda,
  Md., July 2002. Research supported by University
  of California Pacific Rim Research Program

2
Background

• The purpose of this study is to describe the
  exposure to pesticides, and some exposure risk
  factors of Hmong people in northern Thailand
• Hmong are the second largest minority group in
  the border highlands of northern Thailand
• Hmong were traditionally labor intensive, land
  extensive subsistence slash and burn (swidden)
  farmers
• Upland (dry) rice was their main subsistence crop
• Opium was their main cash crop

3

• By the late 1980s Government restrictions on
  access to, and use of land had almost completely
  stopped shifting cultivation and the growing of
  opium poppies.
• At the same time construction of a highland road
  network allowed Hmong farmers to get their bulky
  or perishable products to lowland markets.
• Hmong and other highlanders switched to intensive
  permanent field cultivation of non -narcotic cash
  crops with heavy use of chemicals.

4
Intensive Permanent Field Cultivation, MSM Village
5

• Farmers and their families can be exposed to
  chemicals
• During application, or from drift from
  application
• When in fields or in contact with crops after
  application
• When chemicals are transported or stored
• When in contact with contaminated clothing or
  equipment
• When contaminated clothing or equipment is stored
  or cleaned
• When contaminated food or water is consumed
• Farm families also make use of pesticides in
  their homes for control of mosquitoes, ants,
  cockroaches and mice

6

• Development projects and agriculture officials
  often suggest use of pesticides but give little
  advice to highland farmers on proper use.
• Hmong farmers buy their chemicals from stores in
  town.
• These stores are the major sources of information
  on types of chemicals to buy and methods of use,
  including safety precautions.
• Types of pesticides and other chemicals change
  every year, depending on what is available in the
  market.

7
Hmong farmers use a large number of different
chemicals to control weeds and insects, and to
improve yield and appearance of crops
8

• Hmong use of chemicals is highly seasonal, and
  chemicals are often applied in a cocktail
  including several components (e.g., insecticide
  hormone adherent).

9
(No Transcript)
10
Litchi Tree Loaded with Fruit, KCK Village, April
2002. Farmers believe that fruit at this stage
must be sprayed frequently for best quality,
appearance and price before harvest in May and
June.
11
Information from survey responses indicates there
is little overlap between times of use of
insecticides and herbicides
12
Materials and Methods 1999-2001

• We selected 3 highland rural and one lowland
  urban site to get an idea of the range of
  exposure to pesticides.
• Between 1999 and 2001 we interviewed and screened
  a total of 582 Hmong adult volunteers in 3 rural
  communities where cash crops are grown, and in an
  urban center.
• Interviews included information on socioeconomic
  and demographic characteristics, and pesticide
  related behavior and beliefs.
• We repeated blood draw and surveys in one of
  these communities (KCK) in 2002, and included
  children in the study population.

13
Location of Study Sites MY (1999), KCK (2000,
2002), MSM (2000), CM Urban (2001)
14
Screening for Pesticide Exposure

• We screened for exposure to organo-phosphate or
  carbamate pesticides with a sensitive paper test
  of cholinesterase inhibition (Tovivich 1994).
  The test indicates 4 levels of response
  normal, safe, risky, and dangerous.

15
Results 1999 through 2001

• Risky dangerous levels of cholinesterase
  inhibition
• 20.5 in MY, mid-January 1999
• 29.1 in KCK in mid-February 2000
• 68.9 in MSM in late February-early March 2000
• 56.5 in urban CM, late February 2001
• Highest rates were among individuals of
  reproductive age.
• Women had the same rates as men in MSM, but
  womens rates were lower in other communities.
• Women had less education, less Thai language
  ability, were less likely to have information
  about health risks, and were less likely than men
  to wear protective clothing when applying
  pesticides.
• Many individuals reported symptoms following
  pesticide application.

16
Implications from the 1999-2001 data

• The fact that individuals who do not themselves
  apply pesticides implies widespread environmental
  contamination with pesticides.
• Differences in rates associated with sampling at
  different times of the year implies an
  association between timing of application and
  rate of exposure.
• The generally high rates of exposure among adults
  imply that children may also be exposed.
• Self-perceived symptoms reported to follow
  exposure to pesticides implies that there may be
  health problems associated heavy pesticide
  exposure.

17
Materials and Methods 2002

• In April 2002, in the first stage of a 13-month
  longitudinal study, we enrolled and screened 207
  Hmong residents age gt1 year in 30 randomly
  selected households in KCK, one of the rural
  villages surveyed in 2000
• All study participants age gt15 years were
  interviewed concerning pesticide-related beliefs
  and behavior
• Finger stick blood was collected from all study
  participants for screening tests
• Venous blood was drawn from 2 adults in each
  sample household for analysis of chromosome
  aberrations
• White T-shirts were distributed to two adults in
  each sample household at time of blood draw for
  collection of dust samples
• Water and food samples were also collected for
  analysis

18

• Our current study is designed to capture
  information on seasonal variation in
  pesticide-related behavior and exposure to
  pesticides
• We sampled blood at the time of the heaviest use
  of insecticides (April 2002),
• We will sample again at the end of the period of
  use of herbicides (early October 2002),
• We will sample when little or no pesticide has
  been applied for several months (January 2003)
• We will sample again at the time of heaviest use
  (April, 2003)

19

• We obtained informed consent from all
  participating adults (age gt20) we obtained
  consent from parents for all participating
  children (age lt19) and we obtained informed
  assent for all children age 15-19.

20

• We achieved a high rate of participation from
  registered residents of the randomly selected
  households (207/232 89).
• One randomly selected household declined and was
  replaced.
• Reasons for not participating in screening
• Under 1 year old, 4 (ineligible for this study)
• Working or in school elsewhere, 13
• Temporarily away from village, 5 (in fields 4,
  visiting relatives 1)
• Declined participation, 3
• The very young age distribution of our sample
  population (median age 16 years) is consistent
  with other demographic surveys of the Hmong.

21
(No Transcript)
22
Results 2002

• Social and demographic characteristics
• Education and Thai language ability are strongly
  associated with age and sex
• Younger ages have more education
• Younger ages are more likely to speak Thai and be
  literate in Thai
• Women in older age groups have much less
  education than men, and are much less likely to
  be able to speak Thai
• The bulk of the population (70) is either
  animist or animist Buddhist
• More than 90 of those age gt20 are farmers

23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
Pesticides are applied much more often by men
than by women, and are usually applied by machine
spray
28

• Results of cholinesterase inhibition screening
  for pesticide exposure
• The total of those with risky or dangerous
  levels of cholinesterase inhibition was 156/207
  75.4
• The highest rates of dangerous exposure are
  among children, age 1 through 9 years (39) and
  10 through19 years (26.8).
• Men age 10 through19 and age 20 through 39 have
  significantly higher exposure than women of those
  ages

29
(No Transcript)
30
Highest rates of dangerous exposure are among
children, age 1-9 years and 10-19 years
31

• Substantial numbers of individuals self-reported
  that they experienced symptoms following exposure
  to pesticides, with major differences between men
  and women
• Headache and dizziness were reported more
  frequently by men
• Blurred vision, numbness in feet or hands, or
  itching were reported more frequently by women
• There was no clear pattern of self-reported
  symptoms by age

32
(No Transcript)
33
Pesticide Spray in Litchi Orchard, KCK Village.
Sprayer is not wearing gloves, boots or face mask.
34
Children Play around Spray Equipment with Little
or No Protective Clothing
35

• Large numbers of individuals reported that they
  did not take appropriate precautions to prevent
  exposure to pesticides including wearing masks,
  gloves, boots or protective clothing, or staying
  out of fields after pesticides were applied
• The highest proportions of those who did not take
  these precautions were children age 1 through 9
  years, followed by those age 10 through 19 years
• Women were generally less likely to take these
  precautions than were men

36
Proportions of KCK Respondents Not Using
Protective Clothing when Pesticides Were Applied,
or Not Staying out of Fields after Application,
by Age and Sex
37
Discussion

• Within the past 20 to 30 years Hmong farmers have
  undergone a rapid transition from organic
  labor-intensive subsistence farming to
  chemical-intensive cash crop farming for lowland
  markets.
• Seasonality of use of pesticides implies the need
  to screen at appropriate seasons.
• Screening for cholinesterase inhibition among
  Hmong farmers and their families in northern
  Thailand has shown consistently high rates of
  risky or dangerous exposure to
  organophosphate or carbamate pesticides.

38

• High rates of exposure among all age groups,
  including both those who do and those who do not
  themselves apply pesticides, suggests that
  pesticides are pervasive in the village
  environment.
• The high levels of exposure found among young
  children and the young age structure of this
  population implies an unusually large number of
  children are at risk of high exposure.
• Substantial numbers of individuals report
  symptoms following exposure that are consistent
  with effects of pesticides.

39

• Incomplete use of protective clothing and
  avoidance of fields after pesticide application
  may contribute to high levels of pesticide
  exposure.
• Older villagers, especially women, are less
  likely than younger villagers to have had any
  education and to be able to speak, read or write
  the national language.
• This implies the need for linguistically
  appropriate health education to reduce exposure
  to pesticides.

40

• Use of pesticides is viewed as economically
  essential.
• Parents normally take their children with them to
  the field.
• Children help with tasks in the fields or play in
  the fields during pesticide application, and are
  often at risk of exposure because they very
  rarely take precautions to prevent exposure.
• This implies the need to tailor plans for
  intervention to the local cultural, economic and
  physical environment.

41

• We are reporting results of the research fully to
  village leaders and to study participants, and
  are encouraging them to participate in the
  development of locally appropriate methods of
  reducing exposure, e.g., collaboration among
  villagers to restrict spraying in defined areas
  to specific days, and organizing child care in
  the village to keep young children away from
  spraying and out of sprayed fields.

42
Reporting Results to Villagers and Counseling on
their Meaning
43
Strengths and Weaknesses of this Study

• Strengths
• This study includes a substantial, randomly
  selected population, with a high rate of
  participation.
• Study design is based on knowledge of local
  behavior and the research is conducted with
  active participation of villagers.

44

• Weaknesses
• The rapid screening test using sensitized paper
  is not truly quantitative, and has not been
  compared with a gold standard. We plan to
  assess reliability and validity by comparison
  with standard laboratory methods within the next
  few months.
• The rapid test measures only cholinesterase
  inhibition, presumably from carbamate and
  organophosphates, and does not indicate exposure
  to other classes of pesticides known to be used
  extensively by villagers.
• As yet we have no direct measure of health
  consequences of exposure.

45
Acknowledgements

• We would not have been able to do this study
  without the assistance of many people
• We gratefully acknowledge the assistance of the
  many Hmong villagers who have contributed time as
  participants in this project.
• The staff of the Toxicology Laboratory, Research
  Institute for Health Sciences, Chiang Mai
  University, collected and processed the
  biological and environmental samples,
  efficiently, speedily and with great respect for
  the study participants.
• Staff of the Statistics Department, Research
  Institute for Health Sciences speedily and
  accurately entered the data reported on here.

46

• The staff of the Chet Yawt Subdistrict Health
  Station, Ministry of Public Health graciously
  assisted in medical follow-up.
• Dr. Prasit Leepreecha of the Social Research
  Institute, Chiang Mai University, has
  participated extensively, especially in
  discussions with villagers concerning potential
  interventions.
• Ms. Rasamee Thawsirichuchai, and Mr. Weerachon
  Yangyernkun have participated in all phases of
  planning, community preparation, data collection,
  data coding and interpretation of results.