Explore how food intersects with public health and the environment as it moves from field to plate.
What Are We Feeding Food Animals?
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來自 Johns Hopkins University 的課程
美国食品系统概论：从公共卫生的观点出发
50 個評分
從本節課中
Food Animal Production and Public Health
We will now examine the livestock and seafood industries, which we have touched on in previous modules as a key driver of the global food system. As incomes rise around the world, so too does the global collective appetite for meat. Some of our greatest challenges and debates of the 21st century are rooted in the rising demand for animal protein in an era of dwindling resources and climate change. NOTE: This lecture refers to other lectures offered in this or related full for-credit courses at the Bloomberg School of Public Health.
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Keeve Nachman, PhD, MHSAssistant Professor, Environmental Health Sciences
Bloomberg School of Public Health
Robert S. Lawrence, MDProfessor, Department of Environmental Health Sciences
Bloomberg School of Public Health
Pamela Rhubart BergFood Systems Education Program Manager
Johns Hopkins Center for a Livable Future, Department of Environmental Health and Engineering
Hi this is Kiev Ackman again. Welcome back.
Just talked briefly about how we're raising more food animals than ever.
And in tighter geographic proximity than ever, and now we're going to get into why
that may be problematic from a public health and environmental quality
perspective. Let's start that discussion off by
examining what we actually feed animals that we intend to eat.
We feed food animals antimicrobial drugs and I guess the most commonly recognized
antimicrobial group of drugs are antibiotics, and in certain classes of
animals like cattle, we also feed synthetic hormones.
As I mentioned earlier, later on in this lecture, we're going to go into far
greater detail on the use of antibiotics in food animal production.
We also feed food animals reprocessed animals that die during the production
process and bi-products of food animals that are not considered fit for human
consumption, like feather meal and we'll talk about that in a little bit.
We routinely feed food animals animal waste.
Poultry waste in particular is fed back to poultry and fed to cattle.
And in some cases, we will feed animals waste from industrial processes.
process is. One example of this is that the process
waste from production of brass contains numerous minerals that are considered
beneficial for animals die. Unfortunately,
those process wastes also contains a number of heavy metals that are
considered to be not nutritionally valuable and potentially hazardous to
human health. We've talked about what we're feeding
food animals but how much waste are we talking about when we think about 9.1
billion food animals being produced per year.
To give you a little bit of perspective I wanted to show you some data on processed
human sewage, that are often referred to as human bio solids.
The US population produces about 6.9 million dry tons of processed sewage each
year. And we apply a good fraction of that to
the land, about 3.9 million dry tons. In comparison Animals raised for food in
the US produce 287 million dry tons of waste per year.
And we apply nearly all of that to land. And 1 key difference between human and
animal waste is that we treat human waste before we, apply it to land.
We treat it to remove metals. And we also treat it to kill pathogens.
There's a lot of debate about how effective that treatment is but we're
really not going to go into that here. The issue I'd like to discuss is that we
almost never treat animal waste before applying it to land.
In some cases, we let it compost in piles on fields or we may let it sit in a
lagoon. But we do not go through thorough
treatment processes before we land apply this fertilizer.
And just to give you another factoid, we produce about a dry ton of animal waste
for every US citizen each year. So it's quite a bit of waste and it poses
some serious management challenges. So we've talked about what we feed food
animals and we've talked about how much waste food animals generate, but what's
in animal waste. Well, the first thing I think that you
might hear about quite commonly, when thinking about animal waste, is the
presence of bacteria. And some of those bacteria, because we
feed animals antibiotics, may be resistant to many of the antibiotics that
we use in human medicine. We also find protozoa, parasites in food
animal waste. Certain viruses have been demonstrated to
exist, and persist, for even up to a year in food animal waste.
Food animal waste also has animal dander. Residues of some of those
pharmaceuticals, some of the drugs that I mentioned before.
Heavy metals, hormones, both naturally occurring hormones that animals excrete
in their waste, and some of the Residues of the synthetic hormones that we feed
certain types of food animals. And of course animal waste is rich in
nutrients, nitrogen and phosphorus. Which is why it tends to be applied to
land as fertilizer. We've talked about what's in animal
waste, now what do we do with animal waste.
I mentioned before that we apply most of it to agricultural land as fertilizer.
In some cases we may store it first in hopes to reduce some of the pathogen
loads, and we may store it in lagoons. And this is a picture of a newer lagoon
here. And some cases we may stack it in fields
in long piles called windrows. Recently there's been a lot of attention
towards minimizing the impact of land applied manure on bodies of water like
The Chesapeake Bay. So certain parts of the industry have set
up some alternative treatment strategies to mitigate Some of those concerns.
One of those strategies is development of poultry waste incinerators.
There's a very prominent one operating right now that operates in Minnesota that
burns turkey waste for energy and there are proposals to bring a number of these
to various other states across the U.S., including North Carolina, Maryland And a
few other places. This is a picture of a bag of pelletized
poultry waste and this is something that I've spent quite a bit of time studying,
I actually did some of my doctoral work around pelletized poultry waste and this
bag is from a pelletization facility in Delaware that pelletizes a lot of the
poultry waste that's generated on the Delmarva Peninsula and One reason this is
seen as an alternative to land application, is that pelletized waste can
be loaded into train cars, and then shipped west, or shipped elsewhere, where
it can be sold in fertilizer stores for 25 bucks a pop.
And the last alternative method for managing waste, that wanted to mention
today was feeding a waste back to food animals as we actually mentioned before.
Now, these management strategies pose risks to surrounding communities and
environmental quality for a variety of reasons.
I think first and foremost that the waste rarely stays where it is put.
So, with land application of waste, there's concerns that certain weather
events and precipitation events Are very good at mobilizing some of the nutrients
but also some of the waste born contaminants, both horizontally via
runoff and vertically through leeching into surface and ground water.
Failed storage systems like the one pictured here, this is a ruptured manure
lagoon can spread the contents into the surrounding area and surrounding bodies
of water. Water, and given some of the
micro-biological contaminants that are present in waste, these failures of
storage systems are potentially of concern.
Waste incineration will take any contaminants that are present in animal
waste that are able to survive incineration like heavy metals and
arsenic and introduce them into the air. Anything that isn't cleaned in an air
scrubber prior to leaving an incinerator will stay behind in the ash product
that's left over from the incineration process.
And that ash product is then, as you may have guessed, sold as fertilizer.
Animal-house ventilation can take any of the particulate or micro-biological
contamination that's present inside of a production facility and spread it into
the surrounding community. And, unfortunately, there's very little
data on community and worker exposures to air from animal production facilities.
There's also the potential for direct illegal releases of manure into surface
waters and if you visit EPA's ag website, they actually have a listing of fines
they've issued. For these releases.
And what's interesting is the EPA has been heavily criticized over the years
for being very lax in it's protection of surface waters from animal waste
releases. So you can imagine the idea that they are
actually reporting finds that they're giving means they're really sort of only
getting the tip of the iceberg. What's really important to consider here
is that a number of these pathways are opportunities for waste-born contaminants
to actually get into ground water and what's really key to recognize is that
ground water across the U.S. constitutes 40% of public water supplies.
But for folks in rural areas, especially people who live around these types of
operations Operations, most of them are really on ground water.
It's uncommon in rural areas to see city delivered water, so there is a real
potential for human exposure to these waste born contaniments.
There are a number of other transport mechanisms that I haven't yet mentioned
and I wanted to show you a couple of pictures.
This is one I actually did mention, these are ventelation fans on the side of a
poultry industrial food animal production facilty.
And as you might imagine Anything that's in the air within the facility can be
easily mobilized into the air surrounding these containment structures.
This is a picture I took just upon arriving in Mexico on a sampling trip and
we happened to get stuck behind a poultry transport truck.
And research from colleagues here at Hopkins has actually demonstrated that
poultry transport trucks are very effective methods of transporting
bacteria that are resistant to antibiotics into surrounding communities.
Workers are a wonderful vector, especially for transporting
microbiological hazards from production facilities into the surrounding
communities. Unfortunately, workers are rarely allowed
to access to protective equipment. And in certain types of animal
production, may have. Limited or no access to shower facilities
to decontaminate themselves between work shifts, so they certainly are a means by
which bacteria especially, but also viruses, can be spread.
Collegues at Hopkins have also demonstrated that flies are very
effective vectors for transporting bacteria from food animal production
sites into surrounding communities. Flies have a residency of between 1 and 2
miles so for people who live in rural communities where animals are produced
there are real risks of being exposed to bacteria as a result of deposition from
flies. And the most commonly recognized
transport mechanism is. Probably quite obvious to most of you and
that's transmission of micro-biological hazards or maybe chemical contaminants
through meat. I talked a little bit before about
workers and I just wanted to speak specifically about how workers are really
the front lines in terms of exposures to some of the contaminants that I talked
about on animal waste and certainly some of the contaminants that are present in
animal production facilities. And this is a picture I took on that same
sampling trip in Mexico where we were doing some air sampling and I was able to
catch a couple of pictures around one of the facilities we visited and this was
certainly not an uncommon image among the farms we visited there and from what I've
been told some of the farms here in the states as well.
This young man has the unfortunate job of sweeping swine waste out of a facility
and if you Actually have a look at the waste that he's pushed along to the wall
there. And what you can't see in this photo is.
If he were to continue to move in a forward direction, and, and push the
waste, there's actually sort of a conveyor where
all of the swine waste runs down the side of the building, and into a very large
manure storage pit that's just wide open to the environment.
So what's important to recognize is that there are 5 million documented farm
workers and that includes both crop farm workers and workers in animal production
facilities that may have routine contact via either direct contact with animals or
through contact with animal waste that's used as fertilizer.
So they may come into contact with those waste borne contaminants.
There is no federal oversight of people who work in food animal production
facilities. These facilities have a variety of
exemptions under laws, that would normally require OSHA to actually set up
standards for the workplace. So they are often unprotected.
And as you've seen from some of the photos I've shown you.
Industrial food animal production workers are often not afforded access to personal
protective equipment that might help them minimize their exposures to some of the
hazards that we've described in waste. So they're often unprotected and in some
cases, especially in poultry production, those workers are not offered access to
decontamination facilities like showers. Although research has shown that those
showers can also be a source of exposure to certain pathogens as well.
And lastly, many of the workers go home and spend time with their families and if
they don't have adequate access to protective equipment or decontamination
facilities, their families are at an increased risk of Developing infections
or coming into contact with some of those waste borne contaminants.
I've spoken a couple of times before about some of the concerns over air
quality within animal production facilities, but let's go into some
greater specifics about what's actually there.
So there are wide array of airborne contaminants In these production sites.
I think the most commonly recognized are certain gases like ammonia which is very
common in poultry production facilities. And hydrogen sulfide which is
particularly present in swine production facilities.
There are also an array of papers that examine the composition of volatile
organic compounds that are present at different food animal production facility
types. One of the most recent papers was one
from USDA that looked at a mixture of VOC's that are present in poultry houses
and they speciated, or determined Unique chemicals, for about 60 different
volatile organic compounds in swine production facilities of paper from
earlier, in the 2000s documented 330 unique volatile organic compounds.
What's interesting about those mixtures of volatile organic compounds, is that
the majority of them are not toxicologically characterized, so We not
only can't really make sense of what it means to be exposed to them individually,
but we have even less information about what it means to be exposed to large
mixtures of those chemicals. Animal production facilities tend to be
very dusty places and have higher concentrations of particulate matter.
I've mentioned, extensively, the presence of different bacteria viruses and
protozoa that may become airborne, and available for exposure.
Certain bacteria life may produce endotoxins that have been shown to link
to human morbidity. And animal dander is increasingly
becoming of concern. Concern because of its ability to elicit
allergic responses. As I mentioned before, the health
relevance of all of these is established, but for some of them we're just starting
to understand how they might influence health.
And lastly, I talked about VOC mixtures being challenging to understand because
of the impact of mixtures, but we're talking about not only just mixtures of
VOC's but mixtures of many different types of airborne pollutants and we have
a very, very poor understanding of how they work together to impact health.
So we've talked about workers. We've talked about the air quality inside
of houses. Now, let's talk about rural communities
that surround these production facilities.
Now, I mentioned earlier in the lecture, that these types of operations tend to be
geographically concentrated, so there are communities Where folks will have houses
and those house may be bordered on one, two or three sides by animal production
facility. And you can imagine that there are
concerns that people who live in those houses have impacted quality of life.
And may be at increased exposure to contaminants that emanate from those
facilities. So there have been a number of
epidemiologic studies that have looked at specific health outcomes associated with
being exposed to those contaminants. And the majority have focused on
respiratory and mental health outcomes but there's Documented relationships
between exposure to food animal production contaminants and asthma
prevalence, increased rate of hospitalization, irritation in a variety
of organs including eye, nose and throat. There are studies that look at depression
Anger and anxiety associated with living in close proximity to animal operations.
There been small number of studies that have looked at relationships between
reports of odor and measures of quality of life.
And when you see the subsequent lecture from Steve Wing he's going to go into
greater detail in some of these studies. And there is emerging literature on the
economic effects of owning property, especially houses in Rural areas where
animals are produced. And there have been demonstrations of
decreased property values and property damage associated with living near one of
these types of facilities or living near multiple animal production facilities.
So in closing to this section of today's lecture I wanted to talk about a couple
of challenges and actually conducting public health research on food animal
production sites and characterizing the related public health impact.
I mentioned before that we're dealing with a number of different types of
stressors that are related to producing animals in the current dominant model and
we're talking about exposure to chemicals.
We're talking about exposure to bacteria viruses protozoa.
But we're also talking about other types of stressors that are not always
considered when thinking about environmental health hazards and those
may be social hazards and economic hazards as well.
We are talking about a number of different exposed populations who have
different activity patterns that require in some cases separate evaluation or
examination to study in order characterize exposure in examine outcome.
We do know that certain types of people, or certain sub populations tend to be
more highly exposed to these contaminants.
And I think those in order of exposure would be workers and then fence line and
surrounding communities. And lastly, consumers may suffer from
Certain practices associated with the way that we produce food animals and I'll
talk a little be more about that in the case studies.
It can be challenging to relate some of the adverse effects to exposures due to
access issues to rural communities and production sites.
And that really speaks to the next bullet which is the integrated nature of animal
production. Given these contractual arrangements
between animal producers and the integrator companies it can be incredible
challenging to get access to food animal production sites or animal.
Processing sites, where the animals are converted from live animals into meat.
You may imagine that an integrator company, that owns a processing plant, or
holds a contract over an animal production site, may not be interested in
allowing a public health researcher access to one of those sites.
Because those researchers may find relationships between production
practices. And risks or human illness.
And that may. From an economic perspective, put an
integrator in a vulnerable position. There really are no clear answers to
getting over some of these research barriers.
But I think what's important to recognize is there is a burden that's borne by the
public in terms of concerns related to food safety.
The people who are really. Bearing the burden of our current food
production system are those workers in those rural communities, who really are
the sort of the front lines facing these exposures.
So anyways, that concludes the first part of today's lecture.
The next step will be the case study on antibiotic use in food animal production.
