Yale: Nicole Deziel is an assistant professor at the Yale School of Public Health who studies how exposures to everyday environmental toxins affect human health. In particular, she wants to develop methods that accurately and precisely measure exposure to a host of chemicals that many people encounter and their homes and in their day-to-day lives. Deziel’s work focuses on several pollutants, including pesticides, organic pollutants and PAHs or polycyclic aromatic hydrocarbons that are found in oil and coal, tobacco smoke, and grilled meats. Her work also involves studying the content of vacuum cleaner bags, a great resource for gauging the array of chemical found inside homes. Deziel joined the Yale faculty in 2014.
How important is one’s living area (home and environs) to their physical health?
Our environment has a major impact on our health. The World Health
Organization estimates that 25 percent of the global disease burden is
due to environmental factors, such as contaminated drinking water or
indoor/outdoor air pollution. In the United States we spend upwards of
90 percent of our time indoors. Many of the sources are in our homes,
such as cleaners, pesticides, air fresheners, building materials,
tobacco smoke and mold. Where we live can also have a major impact on
our environmental exposures. Do we live near a major roadway? A farm
where pesticides are applied? A waste incineration plant? Fracking
wells? Pollutants can travel from these sources and penetrate homes. We
come into contact with hundreds of toxic chemicals every day as we move
through our environment. Exposure to any one of these compounds may be
associated with a modest increased risk in an adverse health outcome,
but because many exposures are ubiquitous, the affected population may
be quite substantial.
What are some of the environmental health threats that you have studied?
My work focuses on how to improve our approaches for measuring exposure
to environmental pollutants. Accurate and precise exposure assessment
can substantially enhance our ability to detect exposure-disease
associations. In my work, I study several classes of pollutants, such as
pesticides, persistent organic pollutants (chemicals that are so stable
they will persist in the environment for years to come) and polycyclic
Are people generally aware of these hazards in their homes and living areas?
We come into contact with hundreds of toxic chemicals every day as we
move through our environment. People may not be aware that they are
getting exposed to chemicals because they are “invisible” and the
effects may not manifest for years to come. That being said, there is an
increasing awareness among some segments of the public about the
harmful effects of chemicals in consumer products. Public pressure often
spurs companies to take action, such as the removal of bisphenol-A or
BPA from water bottles.
You’ve incorporated vacuum bags full of dust and dirt into your research. Why do you do this and
what do you find?
I am a big fan of carpet dust. Dust is a reservoir for chemicals in the
home and is an important source of chemical exposure for children. For
example, pesticides are designed to break down outdoors, but resist
degradation in carpet dust due to limited exposure to sunlight,
microbial activity, moisture, and other factors. Pesticides may be
present in carpet dust from drift from nearby treated fields,
application in and around the home and garden or from tracking in on
shoes or clothing. Non-dietary ingestion of dust has been estimated to
contribute up to 40 percent of total pesticide exposure in children,
depending on the pesticide, due to the high percentage of time children
spend indoors and on the floor as well as their propensity to engage in
hand-to-mouth activity. I have observed higher concentrations of
pesticides in households reporting increased treatment of home and
garden pests. I have also observed higher concentrations of dioxins and
furans in the dust of homes located in close proximity to industrial
facilities. Studies in agricultural areas have reported increased
pesticide concentrations in house dust attributable to environmental
sources such as take-home from farm work, agricultural drift and home
What threats do people living on farms face?
Farm families may experience increased exposure to pesticides either
from direct mixing and applying of pesticides, as well as “take-home”
exposure from farm work, “drift” from nearby treated fields, residential
pesticide use and dietary ingestion.
What are the health effects from this type and level of pesticide exposure?
Recent meta-analyses support a link between self-reported residential
pesticide exposure and increased risk of childhood leukemia. Other
research demonstrates a link between pesticide exposure and other
adverse health effects, such as decline in cognitive function in
On a smaller level, is it a good idea to use insect repellent or bug sprays inside the house?
Pesticides are toxic by design—they are intended to kill or control
living things, so minimizing their use is a good idea. I recommend
practicing prevention—such as not leaving food scraps and crumbs,
sealing entry points such as cracks or holes in walls and window
All kinds of materials go into building a house.
Are newer homes generally safer in terms of human health than older
homes that used lead paint and other toxic substances?
Older homes have higher levels of “legacy chemicals,” such as
polychlorinated biphenyls, DDT and lead compared to newer homes. People
can reduce exposure to these compounds by cleaning frequently to reduce
dust, using wet cleaning methods over dry methods, like sweeping, which
tend to resuspend dust. Also, following safe work practices when
renovating. New building materials can also contain potentially harmful
substances, such as volatile organic compounds in paints or flame
retardants in insulation. One solution to pollution is dilution—so if
you are doing painting or renovations, you can reduce exposure by
ventilating your home (i.e., open a window!).