For this video we're going to be starting to discuss toxins and chemicals. And so we're going to be going over a variety of different toxins and chemicals that are present in the environment. Both ones are from natural sources and human sources and discuss some of the implications of those. So the goals for today are for you to know just a few types of toxins and chemicals and some of the sources and effects of those.
So the field of study that we're talking about is environmental toxicology. So that's the study of environmental toxins. That includes a lot of different components including where the toxins may have come from, the sources of those toxins, the what we call the residency time or how long those toxins stay in the environment, their impacts, and how we remove them from the environment once they're already there. So there's a variety of ways you can be exposed to toxins and chemicals in the environment, but the main three are through inhalation, so breathing them in, through ingestion, so eating them, and through contact on your skin.
A lot of the ones we're going to be talking about today will be through ingestion and inhalation, and there's a lot of other ones that can be through skin contact, but that's usually going to be more of an acute type of response. There's a organization headed by the government called the Agency for Toxic Substances and Diseases and they keep track of a bunch of environmental toxins and they produce a report annually to discuss the major environmental toxins, the status of them, their impacts, removal efforts, and a summary of all of that. And so the textbook has a version of this table you can see here with the top 10 toxins as ranked by the agency here.
Now this isn't necessarily the top 10 most deadly toxins out there. It's a combination of how dangerous they are, how many people are exposed to them, how abundant they are in their environment, and then they rank them. And for 2019, which is the most recent one I could find, these were the top 9 substances from the registry list.
And we're going to talk about some of them, but not all of the ones on that list there. And if you want more information about that, scan this QR code over here. So the first one we're going to talk about is arsenic.
arsenic. So arsenic occurs naturally in a lot of different geological, from a lot of different geological sources and so it's ubiquitous through the environment. You can see here in the US, this is a estimate of the number of populations, so the number of people in any different county in the US that are exposed to more than 10 nanograms per liter of arsenic. Now you can see here, so Fresno County is this dog bone one, looks like a little dog bone here, and it's really high. So we have a huge percentage of our population that's exposed to arsenic.
So it's something that's going to be relevant to your life and life of your family. If you want more information on arsenic, I included a QR code here. It takes you to the World Health Organization page and a link here to the USGS, which is the source of this map here. Now, the way most people get exposed to arsenic is through groundwater.
So, like I said, arsenic occurs in natural geological formations in different concentrations, depending on the history of those geological formations. And a lot of the Central Valley here gets their water through groundwater. So that means you have a well, you pump that water up from under the ground and drink it.
And a lot of that will contain arsenic in it. Now there's a lot of side effects arsenic and obviously can be deadly in high concentration But it's also known as a carcinogen We'll talk about this at the end of this little video, but a carcinogen is a cancer-causing Chemical so we know arsenic causes cancer. It's also been linked to cardiovascular disease diabetes And birth defects and so it can be pretty pretty impactful particularly in high concentration so something to keep an eye out for as you think about what your water source is, thinking about buying a house and what the water source for that house might be, and potentially where you want to live, thinking about the environmental pollutants that might be present.
Another one that people are more familiar with is mercury. So mercury also occurs from natural geological formations, but it also occurs from coal and waste burning. So when we burn coal or burn garbage, particularly ones that contain plastic and other oil products, Mercury can be released into the atmosphere. Now the big issue with mercury is it can come in several forms.
It can come in like an aerosolized form and a form that's present as an actual substance in waterways. And so you don't have to know the names of those two types. But the mercury in the air, breathing in mercury, is usually less of an issue and our body can handle it a little bit well than we can when we ingest mercury. And so the common exposure here is when we consume fish. So if there's mercury in the water, small little phytoplankton, zooplankton will start to accumulate that in their tissues.
Then the smaller fish will eat it, the bigger fish eats the small fish, and so on until we eat the bigger fish, like the tuna. And that results in bioaccumulation. So if you remember back when we talked about trophic levels, the amount of biomass that goes up in the environment gets less and less.
So higher trophic levels have less biomass than lower trophic levels. And so if you want to, as a human, gain 10 pounds, you're going to have to eat like 100 pounds of fish. But that mercury is not biodegradable. So that means you're taking all the mercury from all the fish you eat, and it's...
Um... remaining in your tissues. It's bioaccumulating. So the higher up you go in the food chain with bioaccumulation, the more of that toxin that will be present.
And so higher level fish have more mercury in them. We'll see that in a little bit. Now mercury can be dangerous because it particularly damages the central nervous system. It can lead to some major issues.
Over here I included a chart. So it can cause impairment in speech, vision, and gait. So gait is how you walk.
It can cause involuntary muscle movements, it can cause damage to skin and mucous membranes, and it can cause difficulty chewing and swallowing. So three or four of those, or four or five of those, have to do with damage to the central nervous system, damaging the neurons that control your muscular movements. So mercury can be particularly bad.
You'll be particularly warned to stay away from mercury if you're pregnant. And so they often tell you don't eat fish, don't eat seafood. or only eat it like once a month and they're trying to regulate how much mercury that you you're being exposed to.
So here's a little chart that shows how dangerous fish is based on the mercury concentration and you can see down here swordfish and shark are really high and that's because they're top predators in their environments. They eat a lot of the other fish that have bioaccumulated those toxins and so they bioaccumulate them at high levels. Then you have tuna and halibut I mean at moderate levels Flatfish and flounder and pollock a little bit lower.
We got some salmon and some shellfish. So the lower you go in the food chain the less mercury it's going to have. The higher up you go the more mercury.
You can also look over here so this is the fish that you typically buy so typically seafood and the fish that you'll catch it varies it's not quite as straightforward of a diagram. But bass and a pickerel can have quite a bit and while mackerel and smelt won't have quite so much. So the next substance we're going to talk about is bisphenol A or BPA.
And this is a product that's produced when you make plastic. So when we produce plastic, we create bisphenol A. Now, this is a substance that we all consume on a daily basis without really even knowing it. And it's because we get it through our diet, so we ingest it. So it leaches from plastics into our food and into our liquids.
Do you have a water bottle? The bisphenol A will leach from this plastic into that water and when you drink the water you'll get the BPAs. Now there's a growing body of evidence to show that these sort of chemicals are more dangerous than we thought.
So one of them is that they're an endocrine disruptor. And so we have an endocrine system that sends hormones and chemical signals back and forth through our body. These BPAs kind of mimic one of those signals and go and start to muck around with our physiology by sending wrong signals and can cause variety of effects. So in this case it can lead to infertility, early puberty, PCOS, polycystic ovarian syndrome, and a variety of other things.
And that's because a lot of times it's mimicking estrogen and so it's triggering sex hormones in various ways and ways aren't necessarily predictable that are causing health health problems. Now BPAs are extremely common so when they tested I believe it was like almost 3,000 people over six years old They found that BPAs were present in 93% of their urine. So pretty much all of us have BPAs in our bodies. And testing the urine is a way of trying to determine how much BPAs might be present.
So all of us probably have BPAs in our blood, in our bodies. There are some ways you can try and minimize it. One would be to not eat foods that are wrapped in plastic or water that are liquids that are in plastic containers.
But it's kind of hard to avoid that. Even if you get an aluminum soda can, the inside of it will be coated with plastic. And so it will be exposed to BPA. But you can try to minimize the amount of BPAs that leach into your food. So if you have a water bottle and you live in your hot car, the amount of BPAs that will leach into your liquid will be a lot higher.
So cool temperatures, not really hot, not really a long time, so don't source that for too long in the plastic, can reduce the amount of leaching into your food and beverage products. Next one is phthalates. So this is another plastic chemical, but it's used to make plastics flexible. So any plastic that's flexible and kind of doesn't break when you bend it is probably containing phthalates. This is the same exposure pathway as the other one with a few additions.
So again, food and drink contamination. Also interior plastics, so stuff like your mini blinds or wallpapers, cosmetic containers like this one here. toys, they're all going to contain phthalates because they all need to be somewhat flexible. And so they have a similar effect to the BPAs.
They're an endocrine disruptor, but they're a little bit less studied so their specific effects are unclear, but there's growing body evidence that they're probably dangerous and countries are beginning to ban them. So they may potentially be linked to asthma, ADHD, cancer, obesity, and a huge amount of other effects. So this one you get through ingestion because you're you're eating the food and beverage containers that are have been contaminated with it but also through inhalation so when you're in your house and the mini blinds kind of let off a little bit of dust as they kind of degrade you're going to breathe that in and so you're also going to get inhalation of the phthalates and you can scan the qr code to go to the cdc here for more information now another big one is lead so Lead is primarily the primary source of lead is from fossil fuel burning and from industrial practices.
The most common place where people get exposed to lead is actually through paint in their houses. So this isn't typically newer houses, but if you grew up in a relatively old house, you probably had some sort of lead paint in your household. Now, how do you get exposed to that lead paint?
It's not from like eating the lead. It's from the paint in your house deteriorating and turning into dust over time and you're breathing that in. And so you're getting lead exposure through inhalation as your paint kind of turns into dust over time. But luckily in the US at least we have reduced the amount of lead exposure by quite a bit. So these are lead concentrations in the blood of children across the US.
And the red is a 95th percentile. So that's one where it's a huge high number. So most kids didn't reach that level but 50% of kids were here at the median.
So the World Health Organization recommends a maximum lead exposure of five. So up here, prior to 1978, most kids were above that level. On average, kids had three times that amount of lead exposure.
Modern day, we're down below that for the most part. Some kids are still exposed to quite a bit of it. But we've done a pretty good job removing lead from the environment, but it's still a factor. Now, just like some of the other chemicals, the effects of lead are that they attack your central nervous system.
And so they cause damage to your nervous system, which can cause muscular imbalances. Any type of neurological disorder could arise from lead, and it's particularly dangerous to kids. So here's the number of children globally with lead levels greater than what's recommended by the World Health Organization.
So the U.S. has done pretty well now. We generally are below that. But you can see Mexico, parts of South America, parts of Africa, a lot in China and India, Russia, and a variety of other countries in there. And so lead is still globally a pretty big issue.
The next chemical is formaldehyde. So formaldehyde occurs in a lot of places. Our body even makes a little bit of formaldehyde from just chemical reactions that occur, but we can process that away pretty quickly. And so it's found in a lot of different things. Wood products, so if you have treated wood, it'll probably contain formaldehyde.
A lot of cosmetics contain formaldehyde. Industrial practices produce a lot of it. Carpets produce a little bit of formaldehyde, so it's kind of everywhere.
I put this picture here because a lot of animal specimens used to be preserved in formaldehyde, but that's probably just kind of changed now. And it can cause a variety of irritants, including skin and irritation, and it's a carcinogen, so it can cause cancer. If you want more information on formaldehyde, there's a QR code there and a link to the EPA site.
The next one are polycyclic aromatic hydrocarbons or what we guys call pods. Now this is a growing issue and we're going to talk more about this when we talk about air pollution. But so we're going to introduce it now.
But the primary source is from fossil fuel burning or burning other materials. So if you're burning trash or garbage or plastics you can or almost anything like even cigarette smoke if you're burning your meat you can produce polycyclic aromatic hydrocarbons. Now this is just a uh There's a lot of different types. So this is a plural word, meaning there's different types of chemicals. So this is just like a generalized diagram of kind of what their structure would look like.
But they can cause cancer. They can cause cataracts and organ damage, particularly in the kidneys and liver, and a bunch of other effects. And so this is a growing area of concern and one that's receiving a lot of attention as we learn more about what these polycyclic aromatic hydrocarbons can do. So that's kind of our overview of some of the chemicals that we want we're going to talk about.
Now we're going to talk about some generalized terms and health effects. So when you read through the text, listen to these lectures, you might hear the terms acute and chronic effects. So acute effect means small, small time. So it's a result of like a single exposure. Usually we're talking about a large dose in order to elicit a reaction to a contaminant.
So this could be like you're near a wildfire. and you breathe in a huge amount of smoke and your lungs get really irritated and you start to have a lot of like respiratory distress but then when you leave you're treated you're fine afterwards that's an acute effect it's a single dose in large quantities now generally what we're talking about when we talk about environmental toxicology we're talking about chronic effects so this is long-term exposure to a contaminant so we live in the central valley we have horrible air quality here And that means we are constantly being exposed to air pollution in the form of smog, in the form of pesticides, in the form of dust. And so that's in relatively low quantities but over very long periods of time that leads to health disorders.
That's a chronic effect. So small in time but large in quantity. Small in quantity, long periods of time.
You might also see lethal dose. So that's the dose required to kill a human being. How much of that chemical you have to ingest.
or inhale or be exposed to for it to be fatal. You might also see LD50. So LD50 is the dose required to kill 50% of the subjects.
So we use this in science to determine how deadly a substance is and we're usually testing it on mice. So if you expose 100 mice to it, to a certain concentration of that toxin or a certain quantity of that toxin, how much does it take to kill 50% of those mice? And that's a good that's a pretty good measure of how dangerous that toxin is. There's also a variety of types of contaminants and toxins in the way we categorize them.
And we usually categorize them based on the effects that they'll have to our bodies. So we've already talked about carcinogen. So a carcinogen is just something that causes cancer.
So all cells go through what's called mitosis or cell division. That's where one cell turns into two cells and two cells turns into four. And we use that to grow, but also to replace old cells and get new ones going in.
Carcinogens. mess with that system and they cause the cells to replicate too quickly and then you start to get a tumor form so a tumor is uncontrolled cell growth and that can be potentially benign or malignant in a variety of different ways but a carcinogen is one that triggers that process so it triggers cancer and tumor formation So a teratogen is one that affects developing embryos So when you are exposed to the chemical if you are pregnant or you have an embryo then it can cause effects to that that embryo as it develops. A mutagen is one that causes mutations to the DNA.
So we all have the AGTC of our DNA. The mutagens will cause us to replace those letters and that or either take out add additional ones or replace them and that causes the proteins being created by our DNA to change and that can potentially be small or inconsequential or very very damaging and it varies widely. A neurotoxicant is one that affects the nervous system. So neuro, nervous system, toxin. So neurotoxicant has a somewhat sort of effect on the immune, on the nervous system.
That could be causing the way it sends signals to change, causing it to slow down or speed up, causing it to be not capable of sending signals. We talked a little bit about this when we talked about lead and mercury affecting the central nervous system. And then The area where we talk about the most is probably the endocrine disruptors. So these are pollutants that mimic chemical messengers in our body that then go around and kind of run amok in our bodies. sending incorrect signals causing incorrect processes to start or stop and that causes a lot of physiological damage.
So this could be stuff like early puberty, it could be infertility, it could be a variety of different effects and it's very wide ranging because unlike the nervous system where it's a neuron goes from A to B and so you can mess with that and it doesn't mess with too much of it, the endocrine system goes to the whole body. So you dump a chemical into your blood. and it runs throughout your whole body. So these endocrine disruptors can affect wide swaths of your body at a single time.
And so they can be particularly damaging. Okay, so that'll be it for this video. In the next couple of videos, we'll talk about how we remove some of these chemicals and toxins and then kind of move on to disease ecology.