Promoting gender-based analysis in
environmental health research
Donna Mergler PhD
Professor emerita
Center for interdisci...
Lead poisoning in the 1920’ and
1930’s in the United States
– Alice Hamilton (1869 – 1970), the mother of modern occupatio...
Photo: Hanna-Andrea Rother

A similar situation today for
pesticide poisonings?

• In 2002, enhanced surveillance of pesti...
Women Farmworkers in North America
• The percentage of women farm workers is increasing.
– In Mexico, in 1985, the number ...
• “In 2006, there were 15,576 SAWP workers in
Ontario, 393 were women; 75% came from Mexico
• Most of them are single moth...
Same sex, no sex, and unaware sex in
neurotoxicology (Weiss, 2011)

• “Males predominate in behavioral experiments, few su...
Articles in recent volumes of environmental
health journals
No. of
studies

No sex

Stratified
for
sex/gende
r

Animal
stu...
Consequences of not examining
gender and sex differences
• Under-estimation of the environment-related health problems in
...
Gender Differences in
Susceptibility to
Environmental
Factors: A Priority
Assessment

Scientific Group on
Methodologies fo...
Sex and gender
• In 2001, a committee from the Institute of Medicine
provided the following definitions:
– Sex: The classi...
Gender and sex interact throughout the life
span
CONTACT WITH THE
ENVIRONMENT

GENDER

Infant and childhood
experiences
Ad...
Fetal growth and
development
Childhood
growth and
development

•

DBCP, a pesticide used extensively in
banana plantations...
Fetal growth and
development
Childhood
growth and
development
Puberty

Pregnancy
Breast-feeding

Early breast development ...
Childhood growth,
development and puberty

Childhood experiences

• Menarche is occurring at a
younger age
• The period be...
Some examples of sex differences in animal
studies with pre-natal exposures
• Lead (Pb)
•

In rats, lead and maternal stre...
Birth cohort studies
• Some studies have examined sexes separately and reported
differences for some functions but not for...
Intellectual deficits and behavioural
disorders in children

Percentage
of children

50

75

100

125

150

median score
(...
Cognitive performance and environmental Mn
exposure in primary school children
Country

Mn source

Quebec1

Well water

Br...
Low hair manganese : <2µg/g
Quebec
Brazil
Mexico

High hair manganese : ≥2µg/g
Quebec
Brazil
Mexico
Combined analysis of the relation between
hair Mn and Full IQ in primary school children
Quebec
(n = 377)

Mexico
(n = 195...
Estimate : -2.62 (-4.10 - -1.13)

Estimate boys: - 1.08 (-3.21 – 1.05)
Estimate girls: - 4.19 (-6.19 - -2.07)

In a recent...
The cycle of
environmental
disease

Newborn
underweight

0 – 6 months
Further exposure
through breast milk,
but also benef...
Childhood exposures
• Toddlers’ activities may differ between boys and girls
– A study of farm workers’ children showed th...
Childhood socialization : gender identity
• Googled boys and girls e-games

Tank 2008
Choose-your-weapon

Extreme Hair Mak...
Biologic differences and exposure
• A study of serum PCB concentration in adolescents1:
– Girls : positively with milk con...
Gender, sex or both?
• Analysis of Data from the Canadian Health
Measures Survey: Bisphenol A (BPA)
– Males had higher vol...
Urinary Bisphenol-A: data from the
Canadian Health Measures Survey
(geometric means)
2

µg/L

2

1.5

1.5

1

1

0.5
0

2....
Different functions/different exposures
Men

Women

70.0

70.0

60.0

60.0

50.0

50.0

40.0

Series2

30.0

Series3

40.0...
From the Hänninen twin study

Hänninen et al, 1991
Informal work
• A surprising result from our studies on mercury exposure in the
Brazilian Amazon : high blood Pb: mean: 13...
Working together
Community

Natural Sciences &
Engineering

Health Sciences

Social Sciences & Humanities
Cancer among women plastics workers:
an interdisciplinary study1
• Breast cancer risk in relation to occupations with expo...
Gender and sex: not an afterthought
• Taking gender and sex into account begins with the
research question
• Some question...
Study or Intervention Design:
a non-exhaustive list of questions

• If there is exposure assessment, are the activities an...
Data presentation & analyses
Report on Urinary Bisphenol A
(µg/g creatinine)
( Urinary Bisphenol A geometric means)
USA Na...
Complex analyses
• In studies seeking to examine the associations between exposure
and health outcomes, sex/gender is incl...
Sources of
exposure

Biomarkers
of
exposure

Biomarkers
of effect

Health
outcomes

Social
impact

• There is growing awar...
An
Ecosystem
Approach
to Human
Health

biosphere
global ecosystem
regional ecosystem
local ecosystem
community
workplace
b...
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Promoting gender-based analysis in environmental health research

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Do contrasting social expectations along with biological differences lead men and women to be affected differently by environmental contaminants like mercury or pesticides? How do gender and sex interact and impact population health? Professor Donna Mergler has authored more than 150 scientific articles and has given many lectures around the world on the subject, and will share her research on how to promote social and gender considerations when conducting environmental health research.

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Promoting gender-based analysis in environmental health research

  1. 1. Promoting gender-based analysis in environmental health research Donna Mergler PhD Professor emerita Center for interdisciplinary studies on health, well-being, society and environment University of Quebec at Montreal Principal Investigator Canadian Institutes for Health Research Team on Gender, Environment and Health CEC, 2014
  2. 2. Lead poisoning in the 1920’ and 1930’s in the United States – Alice Hamilton (1869 – 1970), the mother of modern occupational health, did much work on lead poisoning – Studies showed women workers had higher lead levels compared to men and the prevalent notion was that women workers were more susceptible to lead poisoning than male workers. – By taking into account job category and socio-economic status, she showed that when men and women were doing the same job, there was no difference in their blood lead levels – Since more women worked in the poorer paying jobs with higher exposures, overall, women had higher blood lead levels as compared to men1. Hamilton A. Exploring the Dangerous Trades, Little Brown & Co., 1943
  3. 3. Photo: Hanna-Andrea Rother A similar situation today for pesticide poisonings? • In 2002, enhanced surveillance of pesticide poisonings in South Africa revealed that, contrary to the official statistics, women had a higher prevalence of pesticide poisonings compared to men1: – higher exposures in women, who did more seasonal work with high exposures and were likewise more exposed in the home. – women’s pesticide-related health problems were often misdiagnosed because of the dominant belief that women were not exposed ‘like men’ to pesticides • In 2004, a field study of 488 migrant workers in Mexico: – women were six times more likely than men to have anemia and asthma, twice more likely to have parasites and respiratory and gastrointestinal diseases and 38% more likely to suffer from heart disease. Significantly more women than men reported symptoms associated with pesticide poisoning2 1. London et al. Int J Occup Environ Health 2002; 8:46-59 2. Palacios-Nava et al. Salud pública de México 2004; 46: 286-293
  4. 4. Women Farmworkers in North America • The percentage of women farm workers is increasing. – In Mexico, in 1985, the number of women in the total population of agricultural workers was about 20%, by 2004 it was estimated at 42.6%1. – In California, women make up 26% of the seasonal agricultural workers2 • An important percentage of farming is done by migrant workers (from one state to another or from one country to another), whose working and living conditions are generally very poor. Researchers from Guelph University have carried out studies with women migrant workers in Ontario3 and produced a fact sheet… 1. cited in Ojinaga et al. in Genero, Ambiente y Contaminación por Sustancías Químicas 2012 p 67-78; 2. cited in Habib and Fathallah, Work 2012;41 Suppl 1:4356-62 2012 3. Preibisch & Encalada Grez, 2010; Journal of Women in Culture and Society 35: 289-316
  5. 5. • “In 2006, there were 15,576 SAWP workers in Ontario, 393 were women; 75% came from Mexico • Most of them are single mothers, in part due to recruitment practices that limit placements in Canada to this group. • They value highly the wages they earn in Canada; the money serves to support their family in Mexico. • Women accede to their employers’ demands in order to maintain their employers’ approval and preserve their tenure in the SAWP, even when these put their health and safety at risk or violate their rights. • Migrant women face greater restrictions on their mobility than men. • They face considerable barriers in accessing public health care and other social services required to address their gender‐specific needs • They face a number of challenges when trying to parent across borders • Migrant women are resilient, innovative individuals pioneering a new life for their families”. Preibisch & Encalada Grez Migrant Workers Fact Sheet, Univerisity of Guelph – Rural Women Making Change 2008
  6. 6. Same sex, no sex, and unaware sex in neurotoxicology (Weiss, 2011) • “Males predominate in behavioral experiments, few such experiments study both sexes, some investigators fail to even describe the sex of their subjects, and in vitro studies tend to wholly ignore sex, even for model systems aimed at neurological disorders that display marked sex differences”. • “In Volume 29 of Neurotoxicology (2008), the male:female ratio of whole-animal, single sex studies was 40:1. Four were on both sexes”. Weiss B. Neurotoxicology. 2011; 32:509-17
  7. 7. Articles in recent volumes of environmental health journals No. of studies No sex Stratified for sex/gende r Animal studies 17 2 (12%) 13 (76%) 1 (6%) 1 (6%) 0 Human studies 25 3 (12%) 4 (16%) 5* (20%) 13 (52%) 6 (24%) * 3 were pregnant women Neurotoxicology : vol 39 (2013); vol 40 (2014) Environmental Health Perspectives: vol 121 (1) (2013) Environmental Research: vol 129 (2014)
  8. 8. Consequences of not examining gender and sex differences • Under-estimation of the environment-related health problems in one sex or the other (usually women) or both • Health problems are attributed to other causes (susceptibility, hysteria, complaining) • Cycle of ignorance : There is less research on the particular situation because it is not viewed as an environmentally-related problem and thus not a “research priority” and thus not studied and if it’s not studied, it’s not a problem • Prevention strategies that target the source, the transmission or the effects of environmental hazards do not necessarily address the entire population.
  9. 9. Gender Differences in Susceptibility to Environmental Factors: A Priority Assessment Scientific Group on Methodologies for the Safety Evaluation of Chemicals (SCOPE, WHO, UNEP, IPCS) 1998 2012
  10. 10. Sex and gender • In 2001, a committee from the Institute of Medicine provided the following definitions: – Sex: The classification of living things, generally as male or female, according to their reproductive organs and functions assigned by chromosomal complement. In most studies of nonhuman animals, the term "sex" should be used. – Gender: A person's self-representation as male or female, or how that person is responded to by social institutions based on the individual's gender presentation. Gender is rooted in biology and shaped by environment and experience 1. Exploring the Biological Contributions to Human Health: Does Sex Matter? Institute of Medicine, 2001
  11. 11. Gender and sex interact throughout the life span CONTACT WITH THE ENVIRONMENT GENDER Infant and childhood experiences Adolescence fetal growth and development Puberty Childhood growth and development SEX Working and family life Retirement Menopause Andropause Reproduction, pregnancy, breastfeeding, Reproduction Decline of biological functions
  12. 12. Fetal growth and development Childhood growth and development • DBCP, a pesticide used extensively in banana plantations rendered men sterile; until the cause was known women were often “accused” of infertility • In utero exposure to many toxics commonly found in our environments will affect developing boys and girls differently • Childhood playing activities and household chores may differ between boys and girls translating into different exposure patterns • Several toxic substances modify the chronology of puberty….. Infant and childhood experiences Puberty Adolescence Reproduction Pregnancy Breast-feeding Working and family life Menopause Andropause Decline of biological functions Retirement
  13. 13. Fetal growth and development Childhood growth and development Puberty Pregnancy Breast-feeding Early breast development in girls after prenatal exposure to non-persistent pesticides Mean age at breast development was 8.9 years in exposed girls vs. 10.4 years in non-exposed. Wohlfahrt-Veje et al, Int J Andrology 2012; 35: 272-282 Mothers working in greenhouses with exposure to pesticides in Denmark
  14. 14. Childhood growth, development and puberty Childhood experiences • Menarche is occurring at a younger age • The period between the appearance of secondary sexual characteristics and menarche is increasing • Secondary sexual characteristics are appearing much younger in girls • Endocrine modifiers may contribute to these changes Pinto, K.. J. Early Adolescence 2007; 27:509-544
  15. 15. Some examples of sex differences in animal studies with pre-natal exposures • Lead (Pb) • In rats, lead and maternal stress interact differently on male and female offsprings’ corticosteroid levels, neurotransmitters and behavior. (Cory-Slechta et al, 2005) • In mice, low level prenatal Pb exposure showed male-specific effects in 1 year old offspring, for motor activity and brain dopamine metabolism; effects were non-linear, with the largest effects at the lower doses (Leasure et al, 2011) • Polychlorinated Biphenyl (PCB) congeners • Sex-specific differences have been reported for motor activity and neurotransmission (Boix et al, 2011), as well as on the retina (Kremer et al, 1999) • Polybrominated diphenyl ethers (PBDE) • No sex differences were observed in male and female mice prenatally exposed to PBDE (Viberg et al, 2004)
  16. 16. Birth cohort studies • Some studies have examined sexes separately and reported differences for some functions but not for others. – Several studies have reported stronger associations between prenatal Pb exposure and poorer cognitive performance and behavioral disorders for boys compared to girls1,2; others have not observed differences3 – Poorer motor performance was reported in relation to prenatal mercury in boys, while other functions were similar4 – Boys presented greater risk for behavioral disorders in relation to prenatal exposure to phthaltes5. – Boys presented greater risk for early childhood symptoms of attention disorders in relation to mothers’ exposure to pesticides6,7, while others have not observed differences8 . 1. Ris et al, 2004; 2. Jedrychowski et al, 2009; 3. Kim et al, 2001; 4. Grandjean et al, 1998 ; 5. Engel et al, 2010; 6. Marks et al, 2010; 7. Fortenberry et al. 2014; 8. Bouchard et al, 2010
  17. 17. Intellectual deficits and behavioural disorders in children Percentage of children 50 75 100 125 150 median score (adapted from Rice, 1998)
  18. 18. Cognitive performance and environmental Mn exposure in primary school children Country Mn source Quebec1 Well water Brazil2 Airborne (Mn alloy production) Mexico3 Airborne (mines and transformation) 1. Bouchard et al, 2011 2. Menezes-Filho et al, 2011 3. Riojas-Rodriguez et al. 2010
  19. 19. Low hair manganese : <2µg/g Quebec Brazil Mexico High hair manganese : ≥2µg/g Quebec Brazil Mexico
  20. 20. Combined analysis of the relation between hair Mn and Full IQ in primary school children Quebec (n = 377) Mexico (n = 195) Brazil (n – 82) p % girls 53.7 48.7 46.3 ns Age 9.1 ± 1.78 9.42 ± 1.45 8.74 ± 1.61 0.007 Full IQ 104 ± 12 78.5 ± 14 85.2 ± 14 0.0001 • Adjusted Full IQ Score for each study separately on mothers’ Raven score, mothers’ education, z-score of height for age • Examined association with hair Mn, taking into account study, age and sex • Stratified for sex, taking into account study and age
  21. 21. Estimate : -2.62 (-4.10 - -1.13) Estimate boys: - 1.08 (-3.21 – 1.05) Estimate girls: - 4.19 (-6.19 - -2.07) In a recent study in the same region in Brazil, externalizing behaviors and attention problem scores were significantly associated with girls' hair manganese levels but not with boys’ (Menezes filho et al. In press) In a study of manganese-exposed adult mice, long-lasting differences in neuronal morphology were observed in females, but not in males, in the absence of differences in manganese accumulation in the brain (Madison et al., 2011).
  22. 22. The cycle of environmental disease Newborn underweight 0 – 6 months Further exposure through breast milk, but also benefits Mothers’ exposures, working and living conditions For boys and men, this can likewise translate into For teenage girls, this higher prevalence of anti-social, delinquent and often translates into criminal behavior early pregnancies Ex: In a longitudinal study of crime arrests in young adults in relation to prenatal and childhood Pb : the attributable risk for 6-y blood lead rate was 0.85 arrests/year for males and 0.18 for females (Wright et al, 2008). Using Indicators to Mesure Progress on Environmental Health, WHO ,UNEP, 2002 Teenager to adult : school drop-out, low paid job, further exposure Age 6 Lack of energy, poor school performance 6 months – 2 y Poverty and lack of parental knowledge. Environmental exposure Age 3 Developmental delays. Child does not demand stimulation. Frequent illnesses
  23. 23. Childhood exposures • Toddlers’ activities may differ between boys and girls – A study of farm workers’ children showed that boys had more frequent contacts with their environment while girls contact objects for longer durations. – The authors point out that “Understanding how frequency and duration contribute to dermal and non-dietary ingestion exposure could increase understanding of the potential difference in exposure between the genders”. (Beamer et al, 2008) • Childhood playing activities and household chores may differ between boys and girls translating into different exposure patterns: • In a study around a dumpsite, boys roamed in contaminated areas more than girls (Steegmann and Hewner, 2000) • Girls may be more exposed to more household contaminants.
  24. 24. Childhood socialization : gender identity • Googled boys and girls e-games Tank 2008 Choose-your-weapon Extreme Hair Make Over Spider-3-rescue Rock Star Make Over Room Clean-up http://www.free-online-games-to-play.net/games/girlgames/page/3/
  25. 25. Biologic differences and exposure • A study of serum PCB concentration in adolescents1: – Girls : positively with milk consumption fat intake , the duration of breast-feeding, and the concentrations of serum triglycerides and cholesterol and negatively with body fat, – Boys: fat intake and serum triglycerides, and marginally with the duration of breast-feeding and negatively with body fat. – Similar and significant estimates for external exposure – Sex-related differences in the serum PCB concentration disappeared after allowing for calculated body fat content – The authors discuss the role of changes in body fat and PCB concentrations throughout the lifespan in women 1. Nawrot et al, 2002
  26. 26. Gender, sex or both? • Analysis of Data from the Canadian Health Measures Survey: Bisphenol A (BPA) – Males had higher volume-based urinary BPA concentrations than did females, but lower creatininestandardized urinary concentrations of BPA. – The reversal in the sex difference was attributed to the higher urinary creatinine concentrations – The authors conclude : “Differences between the sexes in urinary BPA concentrations may reflect differences in exposure and in pharmacokinetic factors, the relevance of which is not currently known” Bushnik et al, 2010
  27. 27. Urinary Bisphenol-A: data from the Canadian Health Measures Survey (geometric means) 2 µg/L 2 1.5 1.5 1 1 0.5 0 2.5 µg/g cr 0.5 6 - 11y 12- 19y 20 - 39y 40 - 59y 60- 79y 0 6 - 11y 12- 19y 20 - 39y 40 - 59y 60- 79y
  28. 28. Different functions/different exposures Men Women 70.0 70.0 60.0 60.0 50.0 50.0 40.0 Series2 30.0 Series3 40.0 unpaid Series1 30.0 20.0 10.0 0.0 total Series5 Series6 20.0 10.0 paid Series4 0.0 15 - 24 25 - 34 35 - 44 45 - 54 55 - 64 65 - 74 75 years years years years years years years old and over 15 - 24 25 - 34 35 - 44 45 - 54 55 - 64 65 - 74 75 years years years years years years years old and over Table 638. Average Hours pers Week Spent Doing Unpaid Household Work and Paid Work by Sex and Age (US Census Bureau, The 2011 Statistical Abstract; The National Data Book) http://www.census.gov/compendia/statab/cats/labor_force_employment_earnings.html
  29. 29. From the Hänninen twin study Hänninen et al, 1991
  30. 30. Informal work • A surprising result from our studies on mercury exposure in the Brazilian Amazon : high blood Pb: mean: 13.1 µg/dL range: 0.59 - 48.3 µg/dL • Highest levels were observed among young men and older women • Partition analysis identified activities with respect to blood Pb Barbosa et al, 2009
  31. 31. Working together Community Natural Sciences & Engineering Health Sciences Social Sciences & Humanities
  32. 32. Cancer among women plastics workers: an interdisciplinary study1 • Breast cancer risk in relation to occupations with exposure to carcinogens and endocrine disruptors: a Canadian case–control study (Brophy et al 2012)1,2 – Many investigators (researchers and community) from different disciplines – Mixed-method research approach (quantitative and qualitative)2 • women in the study area held a wide range of jobs in the plastics industry dating back to the 1960s; • the majority of automotive plastics manufacturing workers in the study area are women; • the work environment is heavily contaminated with dust, vapours and fumes; • there has been a historic failure by government regulators to control exposures; • workers receive a steady dose of mixtures of chemicals through inhalation, absorption and ingestion; • workers are getting sick; and society is largely unaware of their plight. 1. De Matteo et al, New Solutions 2012: 22:427-448 2. Brophy et al. Environmental Health. 2012; 11:87. 3. Winner of the American Public Health Association Scientific Award in Occupational Health
  33. 33. Gender and sex: not an afterthought • Taking gender and sex into account begins with the research question • Some questions … – Are different disciplines and concerned parties providing input? – Is the situation similar for both sexes ? – What are the differences and similarities ? – If just one sex is involved, this should be stated up front (including animal and cell studies1) 1. Ritz et al. First steps for integrating sex and gender considerations into basic experimental biomedical research FASEB J. 2014;28:4-13
  34. 34. Study or Intervention Design: a non-exhaustive list of questions • If there is exposure assessment, are the activities and habits of both genders adequately considered? • If it involves working populations (including informal work), is there a good description of the work activities? • Is the sample size sufficient to demonstrate possible differences? • Are there sex and/or gender-related factors that could influence the relation between exposure and biomarkers of exposure? • Are the outcome measurements relevant for males and females? • Could gender differences influence the outcomes? • Have the individual outcome measures been validated for males and females? • Are the social consequences of effects equally relevant for both genders?
  35. 35. Data presentation & analyses Report on Urinary Bisphenol A (µg/g creatinine) ( Urinary Bisphenol A geometric means) USA National Health and µg/L 2 Survey (2009) Nutrition 1.5 1 0.5 0 6 - 11y 12- 19y 20 39y 40 - 60- 79y 59y 2.5 2 1.5 1 0.5 0 Canadian Health Measures Survey (2010) 6 - 11y 12- 19y 20 39y µg/g cr 40 - 60- 79y 59y
  36. 36. Complex analyses • In studies seeking to examine the associations between exposure and health outcomes, sex/gender is included in multiple regression analyses as any other co-variable like: age, income, and many others… • Some studies suggest that this may not fully capture the sex/gender differences. • Stratifying analyses by sex/gender can help to understand both similarities and differences (both exposure patterns and effect can be different) • Mixed methods, cluster analysis, multi-level analyses have been proposed to examine the complex interrelations between social, physical and biological factors and health outcomes
  37. 37. Sources of exposure Biomarkers of exposure Biomarkers of effect Health outcomes Social impact • There is growing awareness of the importance of including gender. • There is no simple "recipe" for integrating gender and sex in environmental health research - or in examining these complex interrelationships • It requires a change in paradigm to take into account and to promote a bettering understanding of sex and gender in environmental health
  38. 38. An Ecosystem Approach to Human Health biosphere global ecosystem regional ecosystem local ecosystem community workplace biological factors home Health & wellbeing economy geophysical milieu culture toxic substances socio-political situation

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