Marine biotoxins and climate change

I worry about food safety and so it seems do 60% of respondents in a global survey involving 150,000 people in 142 countries. However, while they are mostly concerned about the safety of the current food supply, I worry about the impact of climate change in worsening the food safety situation. We have already covered the impact of climate change on the accumulation of heavy metals and growth of moulds producing mycotoxins.

But of course there is more.

In this last blog in the series covering the food safety impact of climate change we will look at increases in the presence of marine biotoxins produced by blooms of harmful algae.

Toxins produced by some algal species

During recent decades, there has been an apparent increase in the occurrence of harmful algal blooms in many marine and coastal regions. Changes in climate may be creating a marine environment particularly suited to the growth of harmful species of algae. Two major functional groups of marine algae, or phytoplankton, are involved in causing toxic blooms – diatoms and dinoflagellates. There are also toxic cyanobacteria, sometimes called blue-green algae, that are not strictly speaking algae but very similar in action.

Certain toxins produced by these organisms are particularly dangerous to humans. A number of illnesses are caused by ingesting seafood contaminated by the toxins.

The most important harmful algae and their poisoning syndromes include diatoms from the genus Pseudo-nitzschia (amnesic shellfish poisoning), and species of dinoflagellates from the genera Alexandrium, Pyrodinium, and Gymnodinium (paralytic shellfish poisoning), Karenia (neurotoxic shellfish poisoning), Dinophysis and Prorocentrum (diarrhetic shellfish poisoning), and Gambierdiscus (ciguatera fish poisoning). There are also cyanobacteria that produce a range of toxins that can affect humans drinking or swimming in contaminated water causing a similar range of symptoms. Their toxins include microcystin, nodularin, cylindrospermopsin, anatoxin-a, anatoin-a(s), lyngbyatoxin and saxitoxins.

As the names of the syndromes imply the toxins can cause memory loss, digestive problems, seizures, lesions and skin irritations, and finally paralysis that may include the respiratory system. Indeed an impressive list.

Some of these toxins can be acutely lethal and are among the most powerful natural substances known. They affect fish, birds and mammals including humans. Because these toxins are tasteless, odourless, and heat and acid stable, normal screening and food preparation procedures will not prevent intoxication.

Increase in the growth of harmful algae

Dinoflagellate abundances have increased to the detriment of diatom populations in some marine ecosystems linked to increases in sea surface temperatures. This can have serious consequences.

As an example a calculation was performed of the impact of climate change on the length of the period of toxic blooms in Puget Sound, an important area of shellfish farming. Results suggested that by year 2100 the period of optimal growth of the toxic dinoflagellate Alexandrium catenella may potentially expand from 68 days to up to 259 days due to warmer water temperatures. This would have severe implications for regional food safety as A. catenella produces paralytic shellfish poisoning. It would totally close the area for shellfish harvesting for most of the year devastating the local economy.

Another example of a dinoflagellate known to generally favour warmer conditions is Gambierdiscus toxicus, one of the species producing ciguatoxin. Increases in ciguatera fish poisoning has been observed with elevated sea surface temperatures. Clinical signs in humans eating fish containing the toxin include gastrointestinal, neurologic, and cardiovascular signs. Gastrointestinal signs include vomiting, diarrhea, abdominal pain and cramps. Neurologic signs include itching, pain, visual blurring, weakness, depression and headache. Cardiovascular signs include arrhythmia, bradycardia, hypotension, and cardiac block.

Cyanobacteria can reproduce quickly in favourable conditions, where there is abundant sunlight, still or slow-flowing water and sufficient levels of nutrients, especially nitrogen and phosphorus. In still conditions, surface water may form a separate warm top layer in which cyanobacteria is able to access sunlight and nutrients. If these combined factors are present for several days, cyanobacteria multiply and form large blooms. The problem seems to be getting worse. Polluted farm runoff continues largely unabated, and the climate crisis is producing warmer weather and water temperatures, along with more rainfall – all conditions that feed the blooms. News reports of blooms in the USA have increased every year since 2010, when there were a total of 71 stories about outbreaks. In 2018 there were 452 reports about harmful outbreaks.

Incomplete understanding

As already mentioned above harmful algal blooms usually increase during the warm summer months. As daily temperatures continue to rise, the number of days ideal for harmful algal growth increases. As the planet’s oceans warm, coastal regions are seeing more and more algal blooms, often worsened by fertilizer and manure that runs off from farms. With toxic algal blooms becoming more potent and lasting longer, scientists are taking a closer look at their links to a changing climate. What was once considered a summertime matter is now being considered a year-round issue.

However, the extent to which regional climate change will influence harmful algal bloom dynamics is uncertain as separating the effects of climate change from natural variability remains a key scientific challenge. Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. Nonetheless there is only basic information to speculate upon in which regions or habitats harmful algae may be the most resilient or susceptible. 

We can continue to test for the presence of toxins in seafood as is currently the practice in many countries. But the potential escalation of outbreaks could easily overwhelm the system. Should we risk it? I for one worry about the future given the current trajectory of global warming.

Health benefits of pickled capers

If you like to spice your food with capers you may be in luck. Capers are the immature flower buds of the caper bush, Capparis spinosa, growing naturally in the Mediterranean and parts of Asia and Africa. Capers are harvested early in the morning before the heat opens the flower bud. There are also the caper berries, the resulting fruit picked much later in the season.

Archaeological evidence for human caper consumption dates back as far as 10,000 years, according to archaeological findings from Mesolithic soil deposits in Syria and late Stone Age cave dwellings in Greece and Israel.

Multiple health benefits proposed

Pickled capers are common in Mediterranean cuisine, where they provide a salty tang and decorative flair to a variety of meats, salads, pastas and other foods. Apart from the culinary benefits, capers may also have beneficial health effects. Too good to be true, read on and all will be revealed.

Actually, capers have traditionally been used as a folk medicine for hundreds if not thousands of years. True or false, it has been proposed that capers have anti-bacterial, anti-carcinogenic, analgesic, and anti-inflammatory properties. It has also been suggested that capers might strengthen capillaries and inhibits platelet clump formation in blood vessels, relieve rheumatic pain and act as an appetite stimulant. Sounds like a bit much. However, evidence for their efficacy is in some cases supported by clinical findings but as it is often purely anecdotal we need more proof.

Let’s untangle this a bit

It is well known that capers are rich in flavonoid compounds including rutin and quercetin. During the common pickling process of the capers, rutin is further converted to quercetin. This makes pickled capers the richest natural source of quercetin with reported maximum concentrations of 520 mg/100 g. Mechanistically, quercetin has been shown to exert antioxidant, anti-inflammatory, and anticancer activities in a number of cellular and animal models, as well as in humans through modulating the signalling pathways and gene expression involved in these processes.

And now new research from the University of California, Irvine School of Medicine has found that quercetin activates proteins required for normal human brain and heart activity. Specifically, the researchers discovered that quercetin modulates potassium ion channels in the KCNQ gene family. These channels are highly influential in human health and their dysfunction is linked to several common human diseases, including diabetes, cardiac arrhythmia, and epilepsy.

The study revealed that quercetin modulates the KCNQ channels by directly regulating how they sense electrical activity in the cell. In doing so, it tricks the channel into opening when it would normally be closed. Increasing the activity of KCNQ channels in different parts of the body is potentially highly beneficial, suggesting a previously unexpected mechanism for the therapeutic properties of capers.

Alternative sources of quercetin

So now we know that capers are actually good for our health. Capers are also low in calories and high in vitamins and minerals. Unfortunately, they are also high in salt thanks to the way they’re preserved. As they’re bitter on their own, capers are stored in brine or packed in salt. If you’re watching your salt intake that’s worth bearing in mind.

However, don’t despair as there are alternative sources of quercetin. It is found in many fruits, vegetables, leaves, seeds, and grains. Red onions and kale are common foods containing appreciable amounts of quercetin.

So you just have to dig in.

Free to indulge in pizza?

An apple a day keeps the doctor away, as the saying goes. What about a pizza a week keeps you happy and lean? No, I didn’t think you would agree!

You still feel guilty when indulging on a weekly pizza and have to repent by half starving the rest of the week. Well, maybe it is not as bad as you thought according to new research findings. That is if you are a young, healthy male.

The rest of us have to wait until the research has been repeated by including a more representative population.

Anyway, here are the findings

The researchers at the Centre for Nutrition, Exercise and Metabolism at the University of Bath recruited fourteen men with a mean age of 28 years. The men completed two trials in a randomised crossover design, science speak for all participants interchangeably trying two different pizza diets so they in effect were their own controls. The gold standard for small experimental groups.

On each occasion, participants ate a pizza meal. One time they ate until ‘comfortably full’ (ad libitum) and on the other, until they ‘could not eat another bite’ (maximal). The average calorie intake in the all-you-can-eat trial was over 3000 kcal, roughly one and half large pizzas. However, some individuals were able to consume up to two and half large pizzas in one go.

Following each meal metabolic, endocrine, appetite and mood responses were measured. There were marked differences in mood and appetite between trials. After eating maximally, participants felt sleepy and reported no desire for dessert, which was surprising as reward centres in the brain are usually food specific, so eating pizza might not be expected to change the desire for sweet food.

But they found that even when the participants pushed beyond their usual eating limits, doubling their calorie intake, they managed to keep the amount of nutrients in the bloodstream within a normal range. This showed that if an otherwise healthy person overindulges occasionally there are no immediate, negative consequences in terms of losing metabolic control.

Has to be a caveat

Yes, there is a caveat. The researchers had to disappoint by pointing out the long-term risks of over-indulgence with food when it comes to obesity, type II diabetes and cardiovascular disease.

But the good news is that the body can actually cope remarkably well when faced with a massive and sudden occasional calorie excess, being it a huge birthday cake or a Christmas meal. Healthy humans can eat twice as much as ‘full’ and still deal effectively with this huge initial energy surplus.

Just becoming a bit sleepy.

Red wine and/or exercise – your choice

Deteriorating brain function is the bane of getting old. The most severe and debilitating form of cognitive decline is the development of dementia, a collective term used to describe various symptoms of cognitive decline, such as forgetfulness. The estimated proportion of the general population aged 60 and over with dementia at a given time is between 5-8%.

Dementia is not a single disease in itself, but a general term to describe symptoms of impairment in memory, communication, and thinking. Although it mostly affects older people, it is not necessarily a normal part of ageing as it can be influenced by lifestyle factors.

Boosting brain function

Sure, a regular glass of red wine has been shown to have the ability to improve cognitive function as we age. We covered this in detail in a previous blog. But so does regular exercise. Exercise has a broad range of beneficial healthful effects.

A new study published on 9 July 2020 tested the hypothesis that it might be possible to reverse brain ageing through systemic interventions such as exercise. The scientists from the University of California tested whether the beneficial effects of exercise on cognition in aged mice could be transferred in plasma from one mouse to another. Indeed, plasma from young or old mice that had exercised when transferred to other aged mice showed beneficial effects in their brains even if they had not exercised.

How is this possible?

To discover what specific biological factors in the blood might be behind these effects, the amounts of different soluble proteins in the blood of active versus sedentary mice were measured. After some intensive search, the scientists identified the enzyme glycosylphosphatidylinositol-specific phospholipase D1 (Gpld1) as a factor in plasma that might mediate this favourable effect.

Gpld1 is produced by the liver. The team found that Gpld1 increases in the blood circulation of mice following exercise, and that Gpld1 levels correlate closely with improvements in the animals’ cognitive performance.

And not only in rats!

Analysis of previously collected human data showed that Gpld1 is also elevated in the blood of healthy, active elderly adults compared to less active elders.

To test whether Gpld1 itself could drive the observed benefits of exercise, the researchers used genetic engineering to coax the livers of aged mice to produce extra Gpld1, and measured various aspects of cognition and memory. They found that three weeks of the treatment produced similar beneficial cognitive effects as six weeks of regular exercise.

The scientists are now working to better understand precisely how Gpld1 interacts with other biochemical signalling systems to produce its brain-boosting effects (as it doesn’t pass the blood/brain barrier). The hope is to be able to identify specific targets for a future food supplement with Gpld1 that could one day confer many of the protective benefits of exercise for the frail.

So what’s your choice?

So now there is a choice, red wine or exercise or maybe both to retain good cognitive function.

But the question is how much exercise is needed to get the optimal benefit. Would the recommended 10,000 steps a day be sufficient and would a glass of red wine add to the benefit?

Or, horror, would the liver be too busy to metabolise the alcohol from the red wine to have time to also produce the Gpld1?

I want to know more!

Alcohol and brain function in old age

Let’s get this out of the way at the start. It is clear that alcohol misuse is a leading cause of morbidity and mortality. As an example, binge drinking has been shown to lead to a higher risk of cardiovascular disease.

But what about lower level alcohol consumption?

Some previous studies have reported that low to moderate alcohol consumption show benefits to cognitive function. However, others have found no, minimal, or even adverse effects associated with alcohol consumption.

So what to believe?

Association studies are difficult to interpret correctly as most effects studied are multifactorial and vary over time. In particular, a one time measurement can easily be misleading as the time factor is disregarded.

To overcome this challenge, a study published in June 2020 by researchers from the University of Georgia used repeated measurements of health and lifestyle, including questions on drinking habits, in a group of almost 20,000 middle-aged and older participants over a ten-year period.

The participants had their cognitive function measured in a series of tests looking at their overall mental status, word recall and vocabulary. The test results were combined to form a total cognitive score.

And the good news – light to moderate drinking may preserve brain function in older age.

Compared to nondrinkers, those who had a drink or two a day tended to perform better on cognitive tests over time. The optimal amount of drinks per week was between 10 and 14 drinks.

Even when other important factors known to impact cognition such as age, smoking or education level were controlled for, they saw a pattern of light drinking associated with better cognitive function.

The debate will continue

The debate is clearly not over about potential benefits of moderate alcohol consumption. We have written about the balance of the good and bad of alcohol consumption before.

For a while it looked like the fact that regular, moderate alcohol consumption had been shown to promote heart health was settled. And then came another review of previously published research questioning this conclusion.

Several studies pointed to similar protective benefits of moderate alcohol consumption for brain health. And then a systematic review of existing literature on alcohol consumption concluded that there seemed to be no safe level of drinking alcohol.

Believe what you will, but at my age I will cling to the latest findings as it seems to be a solid design of the study.

The benefits of red onions

During the current doom and gloom we need to be cheered up with some positive news. And should you read this when a vaccine has disarmed the coronavirus causing the COVID-19 pandemic in 2020 and governments around the world have taken the necessary actions to limit global warming to 1.5ºC, well, you might still appreciate some good news. 

So here goes.

Multiple health benefits

The next time you go shopping you might reach for red onions. Onions belong to the Allium family of plants, which also includes chives, garlic, and leeks. Farmers have cultivated Allium vegetables for millennia. These vegetables have characteristic pungent flavours and some beneficial medicinal properties. The benefits among many include a reduction of the risk of several types of cancer, improving mood, and maintaining skin and hair health.

Looking back in time, ancient medical texts from Egypt, Greece, Rome, China, and India all cite therapeutic applications for Allium vegetables.

Contemporary studies confirm the early findings. One review from 2015 found a general relationship between an increased consumption of Allium vegetables and a reduced risk of cancer, especially cancers of the stomach and gastrointestinal tract.

Such a relationship was further supported by a 2019 Chinese study that compared 833 people with colorectal cancer with 833 people who did not have the disease. The researchers found that the risk of colorectal cancer was 79% lower in those who regularly consumed Allium vegetables, such as onions.

Experts do not fully understand the exact mechanism by which some compounds in onions inhibit cancer. There are compounds called organosulfurs in onions, some of which have been shown to suppress aspects of tumour growth. However, further research is necessary to confirm which compounds in onion have protective effects against cancer.

But there is more

A wide range of further beneficial effects have also been proven. Different biological properties, such as antioxidant, antimicrobial and anti-diabetic activities, have been reported.

Not surprising as onions are nutrient-dense. One medium onion has just 44 calories but delivers a considerable dose of vitamins, minerals and fibre.

As a good source of vitamin C, onions may support the building and maintenance of collagen. Collagen provides structure to skin and hair.

A 2014 review found that among various activities of Allium vegetables, regulation of hypoglycaemic activity is considered important in helping to control diabetes. Sulfur compounds including S-methylcysteine and flavonoids such as quercetin are mainly responsible for the hypoglycaemic activity. S-methylcysteine and flavonoids help to decrease the levels of blood glucose, serum lipids, oxidative stress and lipid peroxidation, as well as increasing antioxidant enzyme activity and insulin secretion. 

2019 review found that quercetin, a compound in onion skin, had links to lower blood pressure when the researchers extracted it and administered it as a supplement.

Somewhat surprisingly onions have been shown to be able to fight potentially dangerous bacteria, such as Escherichia coliPseudomonas aeruginosaStaphylococcus aureus and Bacillus cereus.

Onions are also rich in B vitamins, including folate (B9) and pyridoxine (B6) playing key roles in metabolism, red blood cell production and nerve function.

Lastly, they’re a good source of potassium, a mineral in which many people are lacking.

I hope you’re convinced by now.

So why red onions?

Any Allium vegetable would do but there is something special with the red colour of red onions.

A Canadian study revealed that the red onion not only has high levels of quercetin, but also high amounts of anthocyanin, which enriches the scavenging properties of quercetin molecules. Anthocyanin is instrumental in providing colour to fruits and vegetables so it makes sense that the red onions, which are darkest in colour, would have the most cancer-fighting power.

There are plenty more benefits associated with Allium vegetables, but this is it for now as I’m off to buy some red onions.

Mycotoxins in a Changing Climate

Global climate change is an issue we should take very seriously now or it will threaten our future food supply. However, I am writing this in June 2020 in the middle of the coronavirus pandemic that is attracting all the attention. There are so far more than 6 million people affected worldwide and soon more than 400,000 deaths.

Most countries, but not all, have reacted with urgency to the acute situation with people movements severely restricted and huge amounts of money spent to support economies. More than one hundred attempts to develop vaccines agains the COVID-19 disease are under way to prevent future outbreaks.

Willingness to limit climate change lacking

We already have the “vaccines” or knowhow to prevent further escalation of the changing climate. Although climate change in the longer term will threaten food security, that is global access to food, and negatively impact food safety with the potential to cause much more pain and suffering, hunger and deaths, it is not getting the same attention as a novel acute disease.

There are many pathways through which climate related factors may impact food safety including: changes in temperature and precipitation patterns, increased frequency and intensity of extreme weather events, ocean warming, and changes in the transport pathways of complex contaminants.

Food security might be the more serious challenge as sufficient access to nutritious food is already an issue in many parts of the world, but long-term quality of life is also threatened by food contamination. We have already covered accumulation of arsenic as an example of heavy metal increases in food caused by climate change. Here we will cover aflatoxin as an example of an increased threat from a range of mycotoxins as fungal growth is influenced by climate change.

Mycotoxin threat will increase

Mycotoxins are compounds naturally produced by a large variety of fungi (moulds) that can cause acute effects, including death, along with chronic illnesses from long-term exposure, including various forms of cancer. It has been estimated that 25% of the world’s yearly crop production is already contaminated with mycotoxins. Mycotoxins are known to occur more frequently in areas with a hot and humid climate.

Aflatoxins, which have the highest acute and chronic toxicity of all mycotoxins, assume particular importance. Aflatoxin produced by Aspergillus flavus and A. parasiticus is a genotoxic carcinogen, but is also a potent acute toxin, and is widely distributed associated especially with maize, groundnuts, tree nuts, figs, dates and certain oil seeds such as cottonseed.

Aflatoxins are a group of approximately 20 related fungal metabolites. They are heat stable and difficult to destroy during processing. Thus exposure, both acute and chronic, can have significant impacts on vulnerable groups, especially babies and children. Four aflatoxins – B1, B2, G1 and G2 – are particularly dangerous to humans and animals.

Health effects of aflatoxin exposure

Outbreaks of acute aflatoxicosis were reported in Kenya in 2004 with 125 deaths resulting from consumption of aflatoxin contaminated maize with repeated events in 2005 and 2006. Most recently several deaths attributed to aflatoxins were reported during the summer of 2016 in the United Republic of Tanzania.

However, chronic effects are much more common. Hepatocellular carcinoma, or liver cancer, is the third leading cause of cancer deaths worldwide, with prevalence 16-32 times higher in developing countries than in developed countries. Of the 550,000-600,000 new cases worldwide each year, about 25,000-155,000 may be attributable to aflatoxin exposure. Most cases occur in sub-Saharan Africa, Southeast Asia, and China with largely uncontrolled aflatoxin exposure in food.

The geographical areas subject to aflatoxin growth in maize and wheat are expected to change with temperature increases – it is predicted that aflatoxin contamination and the associated food safety issues will become prevalent in Europe with a temperature increase of +2°C.

Changes in contamination patterns

Aflatoxin contamination causes significant loss for farmers, businesses, and consumers of varied susceptible crops. Climate change alters the complex communities of aflatoxin-producing fungi. This includes changes in space, time and in the quantity of aflatoxin-producers. Generally, if the temperature increases in cool or temperate climates, the respective countries may become more susceptible to aflatoxins. However, tropical countries may become too inhospitable for conventional fungal growth and mycotoxin production.

Although some regions can afford to control the environment of storage facilities to minimize post-harvest problems, this happens at high additional cost.

Many industries frequently affected by aflatoxin contamination know from experience and anecdote that fluctuations in climate impact the extent of contamination. Climate influences contamination, in part, by direct effects on the causative fungi. As climate shifts, so do the complex communities of aflatoxin-producing fungi. This includes changes in the quantity of aflatoxin-producers in the environment and alterations to fungal community structure.

Fluctuations in climate also influence predisposition of hosts to contamination by altering crop development and by affecting insects that create wounds on which aflatoxin-producers proliferate. Aflatoxin contamination is prevalent both in warm humid climates and in irrigated hot deserts. In temperate regions, contamination may be severe during drought.

Public health threat

As usual prevention is much better than late action to repair already existing damage. This is especially important in at risk regions such as parts of Africa and Asia where the risks of exposure to mycotoxins may increase under predicted climate change conditions.

The combination of future food scarcity and contamination of a larger part of the food supply has the potential of creating an explosive public health threat.

Climate change and food safety

 

global-warming1What has global climate change to do with food safety you ask? Well quite a lot is the unfortunate answer. In a previous blog we have already described the increased risk of finding toxic levels of arsenic in rice due to global warming. Not convinced yet? Maybe the following quotes from a range of official global organisations can provide some compelling information for you to change your mind.

Opinions expressed by some official agencies

The world Health Organization (WHO) writes:

Climate change is likely to have considerable impacts on food safety, both direct and indirect, placing public health at risk. With changing rainfall patterns and increases in extreme weather events and the annual average temperature we will begin to face the impacts of climate change. These impacts will affect the persistence and occurrence of bacteria, viruses, parasites, harmful algae, fungi and their vectors, and the patterns of their corresponding foodborne diseases and risk of toxic contamination. Alongside these impacts, chemical residues of pesticides and veterinary medicines in plant and animal products will be affected by changes in pest pressure. The risk of food contamination with heavy metals and persistent organic pollutants following changes in crop varieties cultivated, cultivation methods, soils, redistribution of sediments and long-range atmospheric transport, is increased because of climate changes.

The European Food Safety Authority (EFSA) writes:

Climate change poses significant challenges to global food safety. Long-term changes in temperature, humidity, rainfall patterns and the frequency of extreme weather events are already affecting farming practices, crop production and the nutritional quality of food crops. The sensitivity of germs, potentially toxin-producing microorganisms and other pests to climate factors suggests that climate change has the potential of affecting the occurrence and intensity of some foodborne diseases. Also, changing conditions may favour the establishment of invasive alien species harmful to plant and animal health. Surface seawater warming and increased nutrients input leads to the profusion of toxin-producing algae causing outbreaks of seafood contamination.

The transmission of infections or diseases between animals and humans (“zoonotic diseases”) is a major source of food safety risks. Environmental factors such as temperature, rainfall, humidity levels and soil can help to explain the distribution and survival of bacteria.

The European Food Information Council (EUFIC) writes:

There is a growing consensus that human activities may be changing our planet’s climate. These changes in climate have a number of possible implications for human health and welfare, one of which could be the safety of food.

It is impossible to accurately assess the full impact of climate change on food safety. However, it is likely that some effect on microbiological and chemical hazards will be seen. The extent of the risk posed by these hazards will depend on the type of hazard and the local conditions and practices.

The Food and Agriculture Organization (FAO) writes:

Climate change does not only imply increased average global temperature. Other effects of climate change include trends towards stronger storm systems, increased frequency of heavy precipitation events and extended dry periods. The contraction of the Greenland ice sheet will lead to rising sea-levels.

These changes have implications for food production, food security and food safety. It is widely understood that the risks of global climate change occurring as a consequence of human behaviour are inequitably distributed, since most of the actions causing climate change originate from the developed world, but the less developed world is likely to bear the brunt of the public health burden.

There is reason to believe that climate change can affect infection of crops with toxigenic fungi, the growth of these fungi and the production of mycotoxins. Given the great importance of this hazard, it is necessary that we understand what changes we might expect in order to better prepare ourselves to deal with this critically important issue.

Changes in climate may be creating a marine environment particularly suited to the growth of toxic-forming species of algae. Toxin-producing algal species are particularly dangerous to humans. A number of human illnesses are caused by ingesting seafood (primarily shellfish) contaminated with natural toxins produced algae; these include amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP), neurotoxic shellfish poisoning (NSP), azaspiracid shellfish poisoning (AZP), paralytic shellfish poisoning (PSP), and ciguatera fish poisoning. These toxins may cause respiratory and digestive problems, memory loss, seizures, lesions and skin irritation, or even fatalities in fish, birds, and mammals (including humans).

Like EFSA, FAO also comments on zoonotic diseases such a hot topic with COVID-19 a prescient example:

Climate change is one of several ‘global change’ factors driving the emergence and spread of diseases in livestock and the transfer of pathogens from animals to humans.

The United States Environmental Protection Agency (EPA) writes:

Climate change will have a variety of impacts that may increase the risk of exposure to chemical contaminants in food. For example, higher sea surface temperatures will lead to higher mercury concentrations in seafood, and increases in extreme weather events will introduce contaminants into the food chain through stormwater runoff.

The United States Department of Agriculture (USDA) writes:

The assessment finds that climate change is likely to diminish continued progress on global food security through production disruptions leading to local availability limitations and price increases, interrupted transport conduits, and diminished food safety, among other causes. The risks are greatest for the global poor and in tropical regions. In the near term, some high-latitude production export regions may benefit from changes in climate.

A bleak future

As you can see a fairly bleak uniform view from many official agencies. Global efforts to reduce greenhouse emissions and regional measures to adapt to changing climatic conditions will be important to mitigate the impact on food and feed safety in relation to human health and nutrition, animal and plant health, and the environment.

The previous blog on arsenic was used as an example of a an increasing human health problem of a contaminant due to climate change. In some future blogs we will cover the the increased prevalence of algal and fungal toxins due to global warming.

Global warming and arsenic in rice

In a series of posts we are going to look at the impact of global warming on food production and the potential for an increase in toxic compounds in our normal diet. First off is rice and higher levels of arsenic found in the rice grain when exposed to higher temperatures during cultivation.

Rice is the world’s most important foodstuff providing nutrients and energy to more than one half of the world’s population. Unfortunately, rice can also contain arsenic, which can cause multiple health conditions and diet-related cancers. In an earlier post we described possible chronic health effects of natural levels of arsenic in food and water.

Here we will cover two issues – the influence of higher global temperatures on arsenic levels in rice and types of arsenic compounds formed in soil under different environmental conditions.

Temperature dependence of arsenic accumulation

Arsenic occurs naturally in soil at different levels across the world. When farmers grow crops like rice under flooded conditions, arsenic is drawn out of the soil and into the water. As rice plants extract water through their roots to its leaves, arsenic follows as it mimics other molecules that rice plants preferentially draw out of the soil.

Now researchers at the University of Washington have found that warmer temperatures, at levels expected under most climate change projections, can lead to higher concentrations of arsenic in rice grains at ranges where they begin to have further health concerns. Arsenic concentrations in the grain more than tripled between the low- and high-temperature treatments.

However, the researchers didn’t have the means to check the type of arsenic compounds found.

Some forms of arsenic are more toxic than others.

It is important to know that not all arsenic is the same as arsenic exists in several different forms. Fish and seafood usually contain high levels of arsenic, but most of this is arsenobetaine, an organic form with little toxicity. It is the inorganic arsenic that can be found in water and rice and a range of other food commodities that has been of particular concern.

However, arsenic speciation is not easy to perform, which has created some confusion. Inorganic and methylated oxyarsenic species have been a focus of research, but thioarsenates, in which sulfur takes the place of oxygen, have largely been ignored.

Now University of Bayreuth researchers, together with scientists from Italy and China, have for the first time systematically investigated under which conditions, and to what extent, sulphur-containing arsenic compounds are formed in rice-growing soils. It turns out that the amounts of thioarsenates formed are linked to the pH-values of the soils and other environmental parameters.

Formation of thioarsenates in soil, their uptake in rice plants and their potential risks to human health urgently require further research as at least one organic sulphur-containing arsenic compound discovered in rice fields is already known to be carcinogenic.

A bad situation potentially made even worse

Arsenic is one of WHO’s 10 chemicals of major public health concern and in particular for the millions of people who rely on rice as their staple food. Young children are also at risk if rice-based products make up a large part of their diet.

Global warming has the potential to make a bad situation even worse. With an increase in global temperatures higher levels of arsenic in rice will follow and the composition of the arsenic compounds may change, for better or worse.

So please be careful in contributing to global warming.

Higher BPA exposure?

Bisphenol A (BPA) can be found in a wide range of plastics, including food and drink containers, and animal studies have clearly shown that it is a hormon disrupting chemical. In particular, foetal exposure to BPA has in those studies been linked to problems with growth, metabolism, behaviour, fertility and even greater cancer risk.

However, so far most government agencies, although acknowledging the potential negative health effects, have considered exposure to BPA to be at safe levels. As an example, the European Food Safety Authority (EFSA) has evaluated the safety of BPA on several occasions since 2006 and in a 2015 full review of exposure and toxicity concluded that BPA poses no health concern for consumers of any age group (including unborn children, infants and adolescents) at current dietary exposure levels.

The public still concerned

Unfortunately, rightly or wrongly, this is a case where the public risk perception differs from the scientific view of the authorities and no official assurances have been enough to allay the public’s concerns. Many plastics manufacturers have reacted accordingly and removed BPA from their products, although alternatives might be as problematic. We have covered the controversy around BPA in several previous blogs.

As the issue is not going away despite government assurances, a range of further studies have been undertaken and numerous research findings published. Some results have been alarming while others have been more reassuring of the safety of BPA.

BPA exposure estimates

A critical factor is a better understanding of the amount of BPA that enters the human body as this is essential for an accurate risk assessment.

There are two ways of measuring such exposure, either by calculating all sources of external exposure or by using biomonitoring of urine excretion as BPA is completely eliminated through urine. However, rapid metabolism of orally ingested BPA means accurate assessment in humans requires not only measurement of BPA but also of its major conjugated metabolites.

Previously, most biomonitoring studies had to rely on an indirect process to measure BPA metabolites, using an enzyme solution made from a snail to transform the metabolites back into whole BPA, which could then be measured.

New surprising findings

In December 2019, a consortium of scientists led by the Washington State University published results from a study using a direct way of measuring BPA that they had developed to more accurately account for all BPA metabolites. This provided the first evidence that biomonitoring measurements relied upon by regulatory agencies in the past could be flawed, considerably underestimating exposure. In their comparative analysis of 29 urine samples from pregnant women, with the direct method they obtained a geometric mean of 51.99 ng/mL total BPA, while the indirect method yielded a geometric mean for total BPA of 2.77 ng/mL, nearly 19-times lower than the direct method.

Importantly, differences between indirect and direct results increased as exposure increased. Because pregnancy causes physiological changes that might affect metabolism of BPA, the scientists also compared indirect and direct measurements on urine samples from five adult men and five non-pregnant women. The results showed the same trends with differences in BPA levels reflecting the inability of the indirect method to accurately measure the levels of metabolites of BPA.

More confusion

There is now even more confusion as the previous EFSA opinion of 2015 had found fairly close equivalence between dietary and biomonitoring exposure results. Would this mean that both measures are wrong and seriously underestimate exposure to BPA? In that case we could have a real problem. Should we be alarmed?

This might all soon be sorted as in 2018 an EFSA working group of scientific experts has again been charged with evaluating recent published findings on BPA with an updated assessment scheduled for 2020. Will this be the ultimate opinion deciding the issue once and for all?

I for one is eagerly awaiting the pending EFSA opinion.