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Tattoos are very popular these days, with about 29% of Americans having one or more. But there also is concern because so little is known about tattoo inks and any health effects on the body, and because adverse effects (e.g. inflammatory reactions) can occur months or years later. One study of 300 people in New York City with tattoos found that 10.3% reported experiencing an adverse tattoo reaction, of which 6% reported suffering from a chronic reaction from a specific color (especially red and black ink) that lasted for more than 4 months.

Now a new study in the journal Scientific Reports reports that microscopic particles from tattoo inks can migrate into the body and wind up in the lymph nodes of the immune system. Most tattoo inks contain particles of varying sizes - with some being very small nanoparticles. The researchers analyzed the skin and lymph nodes of 4 tattooed corpses and 2 corpses with no tattoos. They found the presence of several toxic elements such as nickel, chromium, cadmium, aluminum from the colorful tattoo inks. They found tattoo pigment particles in the skin, and that smaller ink nanoparticles had traveled to the lymph nodes - which leads to chronic enlargement of those lymph nodes, as well as lifelong exposure. From Science Daily:

Nanoparticles from tattoos travel inside the body, scientists find

The elements that make up the ink in tattoos travel inside the body in micro and nanoparticle forms and reach the lymph nodes according to a study published in Scientific Reports on 12 September by scientists from Germany and the ESRF, the European Synchrotron, Grenoble (France). 

The reality is that little is known about the potential impurities in the colour mixture applied to the skin. Most tattoo inks contain organic pigments, but also include preservatives and contaminants like nickel, chromium, manganese or cobalt. Besides carbon black, the second most common ingredient used in tattoo inks is titanium dioxide (TiO2), a white pigment usually applied to create certain shades when mixed with colorants. TiO2 is also commonly used in food additives, sun screens, paints. Delayed healing, along with skin elevation and itching, are often associated with white tattoos, and by consequence with the use of TiO2. 

"We already knew that pigments from tattoos would travel to the lymph nodes because of visual evidence: the lymph nodes become tinted with the colour of the tattoo. It is the response of the body to clean the site of entrance of the tattoo. What we didn't know is that they do it in a nano form, which implies that they may not have the same behaviour as the particles at a micro level. And that is the problem: we don't know how nanoparticles react," explains Bernhard Hesse, one of the two first authors of the study and ESRF visiting scientist.

X-ray fluorescence measurements on ID21 allowed the team to locate titanium dioxide at the micro and nano range in the skin and the lymphatic environment. They found a broad range of particles with up to several micrometres in size in human skin but only smaller (nano) particles transported to the lymph nodes. This may lead to the chronic enlargement of the lymph node and lifelong exposure [Original study.]

 The use of nanoparticles in foods is increasing every year, but we still know very little about whether they have health risks to humans, especially if one is eating foods with them daily (thus having chronic exposure). The nanoparticles in foods are ingredients so small that they are measured in nanometers or billionths of one meter. The most common nanoingredients are: titanium dioxidesilicon dioxide, and zinc oxide. Titanium dioxide is typically used as a "food coloring" to make foods whiter or brighter, but it may or may not be listed on the label. In Europe, this food additive is known as E171. Currently there are no restrictions on using titanium diaoxide nanoparticles in food.

Recent search suggests that there may be health effects from the nanoparticles in our food (here and here), thus we should be cautious. Evidence is accumulating that titanium dioxide nanoparticles can have a negative inflammatory effect on the intestinal lining. Similarly, a new study  looking at both mice and humans suggests that individuals with inflammatory intestinal conditions such as intestinal bowel disease (colitis and Crohn's disease) might have negative health effects from titanium dioxide nanoparticles - that they could worsen intestinal inflammation. Interestingly, the nanoparticles accumulated in spleens of mice used in the study. The researchers also found that levels of titanium were increased in the blood of patients with active colitis. From Science Daily:

Titanium dioxide nanoparticles can exacerbate colitis

Titanium dioxide, one of the most-produced nanoparticles worldwide, is being used increasingly in foodstuffs. When intestinal cells absorb titanium dioxide particles, this leads to increased inflammation and damage to the intestinal mucosa in mice with colitis. Researchers at the University of Zurich recommend that patients with colitis should avoid food containing titanium dioxide particles. The frequency of inflammatory bowel disease like Crohn's disease and ulcerative colitis has been on the rise in many Western countries for decades.... In addition to genetic factors, environmental factors like the Western lifestyle, especially nutrition, play an essential role in the development of these chronic intestinal diseases.

The research of Gerhard Rogler, professor of gastroenterology and hepatology at the University of Zurich, now shows that titanium dioxide nanoparticles can intensify the inflammatory reaction in the bodies of patients with inflammatory intestinal diseases. Titanium dioxide is a white pigment used in medicines, cosmetics and toothpaste and increasingly as food additive E171, for example, in icing, chewing gum or marshmallows. Until now, there have been no restrictions on its use in the food industry.

The scientists led by Gerhard Rogler concentrated their research on a protein complex inside cells: the NLRP3 inflammasome. This protein complex is part of the non-specific immune system, which detects danger signals and then triggers inflammation. If the inflammasome is activated by bacterial components, for example, and the inflammatory reaction plays a vital role in the defense against infective agents. In the same way, NLRP3 can be activated by small inorganic particles -- sometimes with negative consequences: If uric acid crystals form in the cells, for example the inflammation leads to gout.

The research team first studied the effect of inorganic titanium dioxide particles in cell cultures. They were able to show that titanium dioxide can penetrate human intestinal epithelial cells and macrophages and accumulate there. The nanoparticles were detected as danger signals by inflammasomes, which triggered the production of inflammatory messengers. In addition, patients with ulcerative colitis, whose intestinal barrier is disrupted, have an increased concentration of titanium dioxide in their blood. "This shows that these particles can be absorbed from food under certain disease conditions," Rogler says.

In a further step, the scientists orally administered titanium dioxide nanoparticles to mice, which serve as a disease model for inflammatory bowel disease. Here, as well, the particles activated the NLRP3 complex, which led to strong intestinal inflammation and greater damage to the intestinal mucosa in the mice. In addition, titanium dioxide crystals accumulated in the animals' spleens. Whether these findings will be confirmed in humans must now be determined in further studies. "Based on our results," Rogler concludes, "patients with an intestinal barrier dysfunction as found in colitis should abstain from foods containing titanium dioxide."  [Original study.]

 This post is more on the theme of nanoparticles and human health. My last post was about a study that examined how inhaled nanoparticles  (for example, from air pollution) travel from the lungs to the bloodstream. Well, today's post is about a pretty shocking 2016 air pollution nanoparticle study which examined the brains (brain tissue) of 45 dead people  (ages 3 to 92) who had lived for a long time in two places with heavy  particulate air pollution - Mexico City and Manchester, England. Some of the British people also had Alzheimer's disease or dementia.

The researchers found evidence that minute nano-sized particles of magnetite from air pollution can find their way into the brain. There are 2 forms of magnetite (which is an iron ore) - one naturally occurring (jagged edges in appearance), and one found commonly in air pollution (smooth and rounded - from being created in the high temperatures of vehicle engines or braking systems). The researchers are concerned that the air pollution nanoparticles may increase the risk for brain diseases such as Alzheimer's.

One of the researchers (Prof Barbara Maher) has previously identified magnetite particles in samples of air gathered beside a busy road in Lancaster, England and outside a power station. She suspected that similar particles may be found in the brain samples, and that is what happened. "It's dreadfully shocking. When you study the tissue you see the particles distributed between the cells and when you do a magnetic extraction there are millions of particles, millions in a single gram of brain tissue - that's a million opportunities to do damage."..."It's a whole new area to investigate to understand if these magnetite particles are causing or accelerating neurodegenerative disease." However, it must be stressed that at this time there is no proven link between these magnetite particles and any neurodegenerative diseases. They're just wondering.... they call finding these pollution nanoparticles "suggestive observations".

From Medical Xpress: Toxic air pollution nanoparticles discovered in the human brain

Tiny magnetic particles from air pollution have for the first time been discovered to be lodged in human brains – and researchers think they could be a possible cause of Alzheimer's disease. Researchers at Lancaster University found abundant magnetite nanoparticles in the brain tissue from 37 individuals aged three to 92-years-old who lived in Mexico City and Manchester. This strongly magnetic mineral is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which are associated with neurodegenerative diseases including Alzheimer's disease.

Professor Barbara Maher, from Lancaster Environment Centre, and colleagues (from Oxford, Glasgow, Manchester and Mexico City) used spectroscopic analysis to identify the particles as magnetite. Unlike angular magnetite particles that are believed to form naturally within the brain, most of the observed particles were spherical, with diameters up to 150 nm, some with fused surfaces, all characteristic of high-temperature formation – such as from vehicle (particularly diesel) engines or open fires. The spherical particles are often accompanied by nanoparticles containing other metals, such as platinum, nickel, and cobalt.

Professor Maher said: "The particles we found are strikingly similar to the magnetite nanospheres that are abundant in the airborne pollution found in urban settings, especially next to busy roads, and which are formed by combustion or frictional heating from vehicle engines or brakes."

Other sources of magnetite nanoparticles include open fires and poorly sealed stoves within homes. Particles smaller than 200 nm are small enough to enter the brain directly through the olfactory nerve after breathing air pollution through the nose.....The results have been published in the paper 'Magnetite pollution nanoparticles in the human brain' by the Proceedings of the National Academy of Sciences.

A good discussion of the study in The Scientist: Environmental Magnetite in the Human Brain

Fig. S11. Image of magnetite nanoparticles from the exhaust plume of a diesel engine. Credit: Maher et al study, 2016.

09_05_magnetic_01  A microscopic image shows magnetic nanoparticles in the human brain. Credit: Barbara Maher et al study, 2016.

  The use of nanomaterials has been really increasing  in recent years without us really understanding if  nanoparticles have negative health effects, and if they travel to the brain or other organs in the human body. Nanoparticles are used in many  consumer products, including foods (e.g., nano-sized titanium dioxide) and medicines, but they are also found in air pollution  (e.g., tires breaking down, vehicle exhaust). Well..... evidence is starting to appear that YES - nanoparticles can travel  throughout the body, and they can accumulate in the body, including lungs and brain, and they can have negative health effects. For example, inhaled nanoparticles from air pollution are able to deposit deep in the lungs where they cause oxidative stress and inflammation.

Now new research in both humans and mice has shown that inhaled nanoparticles can travel from the lungs into the bloodstream. In this study both healthy males and heart disease patients inhaled gold nanoparticles of varying sizes. The gold was detected in the blood and urine within 15 minutes to 24 hours after exposure, and was still present 3 months after exposure. The levels were greater following inhalation of smaller 5 nanometer (nm) particles compared to the larger 30 nm particles (meaning the body had trouble clearing the smaller nanoparticles). The nanoparticles acculmulated more in inflamed vascular sites, including carotid plaques in patients at risk of a stroke. Showing this is important in explaining how tiny nanosized particles in air pollution are linked to cardiovascular disease and death - for example, why and how they can trigger heart attacks and other "cardiovascular events". Science Daily:

Nanoparticles can travel from lungs to blood, possibly explaining risks to heart

Tiny particles in air pollution have been associated with cardiovascular disease, which can lead to premature death. But how particles inhaled into the lungs can affect blood vessels and the heart has remained a mystery. Now, scientists have found evidence in human and animal studies that inhaled nanoparticles can travel from the lungs into the bloodstream, potentially explaining the link between air pollution and cardiovascular disease. Their results appear in the journal ACS Nano.

The World Health Organization estimates that in 2012, about 72 percent of premature deaths related to outdoor air pollution were due to ischemic heart disease and strokes. Pulmonary disease, respiratory infections and lung cancer were linked to the other 28 percent. Many scientists have suspected that fine particles travel from the lungs into the bloodstream, but evidence supporting this assumption in humans has been challenging to collect. So Mark Miller and colleagues at the University of Edinburgh in the United Kingdom and the National Institute for Public Health and the Environment in the Netherlands used a selection of specialized techniques to track the fate of inhaled gold nanoparticles.

In the new study, 14 healthy volunteers, 12 surgical patients and several mouse models inhaled gold nanoparticles, which have been safely used in medical imaging and drug delivery. Soon after exposure, the nanoparticles were detected in blood and urine. Importantly, the nanoparticles appeared to preferentially accumulate at inflamed vascular sites, including carotid plaques in patients at risk of a stroke. The findings suggest that nanoparticles can travel from the lungs into the bloodstream and reach susceptible areas of the cardiovascular system where they could possibly increase the likelihood of a heart attack or stroke, the researchers say. [Original study.]

  Did you know that some foods have nanoparticles added to them? Which means that you may be ingesting food nanoparticles without knowing it. There are currently hundreds of foods with nanoparticles in them, and it is estimated that people (in developed countries) consume more than 1012 nanoparticles in foods each day. The nanoparticles in foods are ingredients so small that they are measured in nanometers or billionths of one meter. The most common nanoingredients are: titanium dioxide, silicon dioxide, and zinc oxide.

What, if anything, do nanoingredients do to humans? That is, are there any effects from ingesting them? Several articles in the past year raise a number of concerns, especially because so much is still unknown. Two recent studies, one done in the US. (using an intestinal model) and one in France (using rats) also raise similar health concerns.

The U. S. study found that the ability of small intestine cells to absorb nutrients and act as a barrier to pathogens is "significantly decreased" after chronic low-level exposure to nanoparticles of titanium dioxide. It affected the surface of the intestinal cells, called microvilli, of the small intestine in a negative way (it "induced a significant decrease in absorptive microvilli"). The French study found that 100 days of chronic low-level ingestion of titanium nanoparticles in food resulted in intestinal inflammation, that it crossed the intestinal barrier and passed into the bloodstream (and even to the liver), and there was development of "preneoplastic lesions" - thus leading the researchers to suggest that chronic low-level exposure plays a role in initiating and promoting early stages of colorectal cancer (colorectal carcinogenesis).

Meanwhile the use of nanoingredients is unregulated in the U.S., and the number of foods with nanoingredients is growing rapidly. About 36% of the titanium dioxide used in food is in titanium dioxide nanoparticle form. It is frequently found in processed foods such as candies, icing, and chewing gums, and is primarily used to make the food whiter or brighter. In the European Union titanium dioxide nanoparticles used as a food additive is known as E171.

Nanoparticles are typically used in foods as additives, flavorings, coloring, or even coatings for food packaging (which can then migrate or leach into food). It is thought that nanocoatings are being used on some fruits and vegetables. Even though ingredients such as titanium dioxide are considered to be "generally recognized as safe" (GRAS) before they're made into nanoparticles, the question is whether they’re safe in their nanoparticle form. This is because nanoparticles can exhibit new or altered properties at nanoscale dimensions. Some concerns about nanoparticles are that they are small enough to penetrate the skin, lungs, digestive system, and perhaps pass through the blood-brain barrier and placental-fetal barrier, and cause damage. Some earlier studies raised the question of whether low-level inflammation of the intestines from chronic (daily) nanoparticle ingestion is contributing to intestinal bowel diseases or the development of colorectal cancer in humans. This research is in its infancy. Whew... So if this concerns you, how can you avoid nanoparticles in food? Read food ingredient lists to avoid titanium dioxide, silicon dioxide, zinc oxide, and cut back (or avoid) eating processed foods as much as possible.

From Science Daily:  Food additive found in candy, gum could alter digestive cell structure and function

The ability of small intestine cells to absorb nutrients and act as a barrier to pathogens is "significantly decreased" after chronic exposure to nanoparticles of titanium dioxide, a common food additive found in everything from chewing gum to bread, according to research from Binghamton University, State University of New York. Researchers exposed a small intestinal cell culture model to the physiological equivalent of a meal's worth of titanium oxide nanoparticles -- 30 nanometers across -- over four hours (acute exposure), or three meal's worth over five days (chronic exposure).

Acute exposures did not have much effect, but chronic exposure diminished the absorptive projections on the surface of intestinal cells called microvilli. With fewer microvilli, the intestinal barrier was weakened, metabolism slowed and some nutrients -- iron, zinc, and fatty acids, specifically -- were more difficult to absorb. Enzyme functions were negatively affected, while inflammation signals increased. "There has been previous work on how titanium oxide nanoparticles affects microvilli, but we are looking at much lower concentrations," Mahler said. "We also extended previous work to show that these nanoparticles alter intestinal function."

Titanium dioxide is generally recognized as safe by the U.S. Food and Drug Administration, and ingestion is nearly unavoidable.[Note: the FDA does not distinguish between regular titanium dioxide and titanium dioxide nanoparticles.] The compound is an inert and insoluble material that is commonly used for white pigmentation in paints, paper and plastics. It is also an active ingredient in mineral-based sunscreens for pigmentation to block ultraviolet light. However, it can enter the digestive system through toothpastes, as titanium dioxide is used to create abrasion needed for cleaning. The oxide is also used in some chocolate to give it a smooth texture; in donuts to provide color; and in skimmed milks for a brighter, more opaque appearance which makes the milk more palatable. "To avoid foods rich in titanium oxide nanoparticles you should avoid processed foods, and especially candy. That is where you see a lot of nanoparticles," Mahler said. [Original study.]

From Science Daily: Food additive E171: First findings of oral exposure to titanium dioxide nanoparticles

Researchers from INRA and their partners1 have studied the effects of oral exposure to titanium dioxide, an additive (E171) commonly used in foodstuffs, especially confectionary. They have shown for the first time that E171 crosses the intestinal barrier in animals and reaches other parts of the body. Immune system disorders linked to the absorption of the nanoscale fraction of E171 particles were observed. The researchers also showed that chronic oral exposure to the additive spontaneously induced preneoplastic lesions in the colon, a non-malignant stage of carcinogenesis, in 40% of exposed animals. Moreover, E171 was found to accelerate the development of lesions previously induced for experimental purposes. While the findings show that the additive plays a role in initiating and promoting the early stages of colorectal carcinogenesis, they cannot be extrapolated to humans or more advanced stages of the disease. The findings were published in the 20 January 2017 issue of Scientific Reports.

Present in many products including cosmetics, sunscreens, paint and building materials, titanium dioxide (or TiO2), known as E171 in Europe....Composed of micro- and nanoparticles, E171 is nevertheless not labelled a "nanomaterial," since it does not contain more than 50% of nanoparticles (in general it contains from 10-40%). The International Agency for Research on Cancer (IARC) evaluated the risk of exposure to titanium dioxide by inhalation (occupational exposure), resulting in a Group 2B classification, reserved for potential carcinogens for humans. [Original study.]

 Did you know that some foods have nanoparticles added to them? Which foods? Nanoparticles in foods are ingredients so small that they are measured in nanometers or billionths of one meter. The most common nanoingredients are: titanium dioxide, silicon dioxide, and zinc oxide. What, if anything, do nanoingredients do to humans? That is, are there any effects from ingesting them? No one really knows. However, several articles in the past year raise a number of concerns, especially because so much is still unknown. Meanwhile the use of nanoingredients is unregulated in the U.S., and the number of foods with nanoingredients is growing rapidly.

Nanoparticles are typically used in foods as additives, flavorings, coloring, or even anti-bacterial coatings for packaging. It is thought that nanocoatings are being used on some fruits and vegetables. Even though ingredients such as titanium dioxide are considered to be "generally recognized as safe" (GRAS) before they're made into nanoparticles, the question is whether they’re safe in their nanoparticle form. This is because nanoparticles can exhibit new or altered properties at nanoscale dimensions. Some concerns about nanoparticles are that they are small enough to penetrate the skin, lungs, digestive system, and perhaps pass through the blood-brain barrier and placental-fetal barrier, and cause damage.

A 2016 report by Friends of The Earth reported finding nanoparticles in various brands of baby formulas. None listed nanoparticles as ingredients, but independent laboratory testing found the baby formulas to contain them. The Medscape article (below) reported on recent research  that suggested that nanoingredients can cause problems such as intestinal inflammation, especially for certain groups, such as those with intestinal bowel disease (IBD). According to the Science News article (below): "Tests show that on average more than one-third of the titanium dioxide in foods is in the form of nano-sized particles."

The Center For Food Safety states: "Bulk scale titanium dioxide is used as a food coloring agent, often to make foods look whiter or brighter, but the FDA has not set exposure limits yet for its use at the nano scale in the US. Moreover, the largest review of nano titanium dioxide studies show that many basic questions have not been answered. Candies like M&M’s, processed cheeses, and chewing gum have all been found to contain nano titanium dioxide.  Nano titanium dioxide is small enough to cross through the intestine and into organs where it can damage DNA and disrupt cell function." They have established a searchable data base of foods containing nanoparticles. The list is incomplete, but some popular foods containing nanoingredients (may not be on ingredient list, but lab tests found them) include: M&Ms, Lindt chocolate, Dannon Greek Plain Yogurt, Cadbury Milk Chocolate bars, Nabisco Chips Ahoy cookies, and Nabisco Oreos.

From Medscape [UPDATE: The Medscape link no longer works. Link to original study and to a discussion of the research in The Rheumatologist.]:  Titanium Dioxide Additives May Boost Intestinal Inflammation

Murine [mice] and other studies suggest that titanium dioxide (TiO2) nanoparticles, widely used as food additives and in drug formulations, may be involved in intestinal inflammation, according to Swiss researchers..... "It seems that titanium dioxide nanoparticles are not harmful for a healthy person with a normal intestinal barrier. But this may be different in an individual with impaired intestinal barrier function such as patients with inflammatory bowel disease (IBD).".... IBD is increasing in many nations undergoing westernization. Among possible causes are microparticles of agents such as Ti02, which are used to improve the appearance of products including food.

The researchers go on to point out that there is increasing evidence that exposure to TiO2 "can cause adverse effects, including the production of reactive oxygen species (ROS) inflammatory responses and tumor formation.".....Finally, wrote the investigators, "An increase of titanium burden in blood of patients with ulcerative colitis having active disease was found, evidencing an impaired barrier function and suggesting that TiO2 nanoparticles could pose a specific risk to patients with IBD."

Good eye-opening article. From Science News: Nanoparticles in foods raise safety questions

It seemed like a small thing when Paul Westerhoff’s 8-year-old son appeared, with his tongue and lips coated bright white. The boy had just polished off a giant Gobstopper, a confectionery made of sugary, melt-in-the-mouth layers. Curious about the white coating, Westerhoff, an environmental engineer, pored over the jawbreaker’s contents and discovered just how incredibly small the matter was. Among the Gobstopper’s ingredients were submicroscopic particles of titanium dioxide, a substance commonly added to plastics, paint, cosmetics and sunscreen. At the time, Westerhoff’s lab group at Arizona State University was actively tracking the fate of such particles in municipal wastewater systems across the nation.

Titanium dioxide is also a food additive approved by the U.S. Food and Drug Administration. Ground to teensy particles measuring just tens of billionths of a meter in size — much smaller than a cell or most viruses — titanium dioxide nanoparticles are frequently added to foods to whiten or brighten color. 

Weeks after his son’s candy-coated encounter, Westerhoff went to the supermarket, pulled more than 100 products off the shelves and analyzed their contents. His findings, published in 2012 in Environmental Science & Technology, show that many processed foods contain titanium dioxide, much of it in the form of nanoparticles. Candies, cookies, powdered doughnuts and icing were among the products with the highest levels. Titanium dioxide is also found in cheese, cereal and Greek yogurt.

Titanium dioxide isn’t the only nanoingredient added to food. Various other materials, reduced to the nanoscale, are sprinkled into food or packaging to enhance color, flavor and freshness. A dash of nano will smooth or thicken liquids or extend the shelf life of some products. Scientists have designed nano-sized capsules to slip beneficial nutrients, such as omega-3 fish oil, into juice or mayonnaise, without the fishy taste.  

But as scientists cook up ways to create heart-healthy mayo and fat-fighting ice cream, some are also considering the potential risks that might accompany the would-be benefits. Because of their small size, ingested nanoparticles may interact with cells or behave differently than their bulkier counter-parts. So far, less-than-perfect laboratory studies offer contradictory results.

Researchers, including those developing nanofoods, say more information is needed on the ingredients’ potential impacts. Current studies, limited to mice or lab dishes, often analyze megadoses of particles far beyond what any normal diet would include. Scientists need a better handle on what happens when people nosh on nanolaced foods daily, taking in small doses at a time, says Ohio State University pathologist James Waldman. He and others are devising tests to find out.

So far, only a few nanoingredients are added directly to foods or packaging: Titanium dioxide, silicon dioxide and zinc oxide are the most common. Larger versions of these ingredients have been used in food and medicines for decades and are considered “generally recognized as safe” by the FDA, which requires that any substance added to food be evaluated for safety.

Scientists have developed numerous ways to test the safety of substances that go into food, but most of the tests were designed decades ago, before ingredients began to go nano. Titanium dioxide, for example, was evaluated in the late 1960s, using particles larger than 100 nanometers. Human cells were exposed to the substance to test for toxic effects and to work out how much of it can be safely consumed. But those safety tests may not apply to some nano-substances. Size and surface features can improve or impair a nanoparticle’s ability to enter cells. Some nanoparticles — including those considered safe by the FDA — interact with cells in odd or unexpected ways, according to several recent studies.

Most studies of nanoparticles in food focus on the gastrointestinal tract — the mouth, esophagus, stomach and intestines. Waldman’s group at Ohio State is tracking the fate of nanoparticles once they’re swallowed to see if they travel beyond the gut. In February, the researchers showed that nanoparticles force-fed to mice can reach the liver, kidneys, lungs, brain and spleen. Details were published in the International Journal of Nanomedicine. “Particles are getting into the bloodstream, and once they’re there, they can go to any other organ,” Waldman says.

The FDA has not erected new hoops for food manufacturers that use nanoparticles. Requests to use a food ingredient at the nanometer scale are subject to the same safety requirements applied to other food additives, according to FDA press officer Megan McSeveney. Manufacturers must demonstrate that the substance is safe under the conditions of its intended use. In June 2014, the agency issued guidelines that go only as far as advising manufacturers to consult with the government before launching nanotechnology products.....Meanwhile, scientists agree that, based on studies to date, the nanofoods found on supermarket shelves are probably safe to eat — when consumed at “typical” quantities.