Category Archives: Environmental Pollutants

Nanoparticles and gut effects – generally recognized as safe?

Models for oral uptake of nanoparticles in consumer products

Titanium dioxide nanoparticle ingestion alters nutrient absorption in an in vitro model of the small intestine

Zhongyuan Guo, Nicole J. Martucci, Fabiola Moreno-Olivas, Elad Tako, Gretchen J. Mahler. Titanium dioxide nanoparticle ingestion alters nutrient absorption in an in vitro model of the small intestine. NanoImpact, 2017; 5: 70 DOI: 10.1016/j.impact.2017.01.002

In the study above, researchers took 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) and determined the effect on the gut. Acute exposure caused no harm,  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. It turns out that nanoparticles are everywhere, especially in food, cosmetics, and pharmaceuticals. It can enter the digestive system through toothpastes, since 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. Dunkin Donuts stopped using powdered sugar with titanium dioxide nanoparticles in 2015 in response to pressure from the advocacy group As You Sow.

There is emerging evidence that we have generated strategies to utilise nanoparticles for dietary and physiological benefit evolutionarily.  Thus, nanoparticulate structures are neither inherently toxic nor inherently safe: like all molecules these decisions will rest upon molecular structure, biological environment, degree of exposure and host susceptibility.

Nanoparticues act in a number of wasy internally, especially in the gut lumen, where they are exposed to mucin, proteins, pH changes, and other existing charged particles. There has been described a protein coating of nanoparticle surfaces, referred to as a ‘corona’, this phenomenon has been known for decades and will inevitably happen in the particle’s native environment. In the gastrointestinal tract it is likely that the acidic pH of the stomach, which mainly is maintained even postprandially, and the presence of gastrointestinal enzymes, will serve to denude ingested particles of their surface-adsorbed molecules but then re-adsorption of novel entities will occur in the less acidic small bowel lumen.

There are many exogenous inorganic particles are man-made particles comprising titanium dioxide or silicates/aluminosilicates. Titanium dioxide (designated E171 in Europe) is used for whitening and brightening foods, especially for confectionary, white sauces and dressings, and certain powdered foods.

Titanium dioxide (designated E171 in Europe) is used for whitening and brightening foods, especially for confectionary, white sauces and dressings, and certain powdered foods. It is also used in the pharmaceutical industry as an opacity agent. Titanium dioxide is typically found in gut tissue in the anatase polymorphic form and is a 100-200 nm diameter spherical particle that is resistant to gastrointestinal degradation. Particulate silicates and aluminosilicates (E554, E556 and E559 in Europe) are used in the food industry as anti-caking agents and to allow the flow of powders, and some are present in cheeses, sugars and powdered milks. In the UK, the major five food sources of particulate silicates are salt, drinking powders, chewing gum, instant pot savory snacks and icing sugar.Overall, intake of dietary inorganic microparticles in the UK has been estimated to be about 40 mg/person/day (35 mg for the silicates and 5 mg for titanium dioxide) which equates to a staggering daily exposure of 101214 particles/person.

How are  the partciles taken up in the gut? M-cell-uptake (transcytosis) at the surface of intestinal lymphoid aggregates is the quintessential pathway for gut particle uptake and is very well described, especially for large nanoparticles (20-100 nm) and small microparticles (100-500 nm). Hydrophobic particles appear to be much better taken up than hydrophilic particles,  and  generally, small particles are better taken up than large ones with, perhaps, an optimal size of around 50 nm diameter.

Other sources of nanoparticles (NM) relevant for oral exposure comprise mainly cosmetics (sunscreen, lipsticks, skin creams, toothpaste) and food (packaging, storage life sensors, food additives, juice clarifiers). Whereas NMs in food are intended to be ingested, nanoparticles for instance in cosmetics and ingredients in food packaging may accidently get into the gastrointestinal tract. Major materials used in these products are: silver, and metal oxides of zinc, silica, and titanium. Nanosilver (Ag) is used in food packaging. According to the Woodrow Wilson Nanotechnology Consumer Products Inventory 2011, Ag nanoparticles are the most commonly used new NM in consumer products followed by TiO2, ZnO, platinum (Pt) and silicium oxide NMs ( Although gold NMs are also used in cosmetics, food packaging, beverage and toothpaste their main applications are in the medical field.

Decrease of particle size in the nanoscale has been identified as a main parameter for the increased toxicity of different materials. Polystyrene, for instance, is a very biocompatible polymer used in cell culture. Nanoparticles, however, made from this material are cytotoxic.

Compared to other metal and metal oxide nanoparticles intake of TiO2 by food is relatively high at 5 mg TiO2/person/d .Metal and metal oxide nanoparticles can accumulate in plants  and in animals of the food chain. That is worrisome.

A number of factors effect uptake of particles by the gut. Even in healthy individuals gastrointestinal transit is by far not constant and shows considerable variation through the large intestine . These effects are known to influence oral bioavailability of conventional drugs but are even more important for the effects of NMs because NMs readily adsorb proteins. Mucus represents an efficient acellular barrier. Mucus consists of mucin proteins (highly glycosylated extracellular proteins with characteristic gel-forming properties), antiseptic proteins (lysozyme) and other proteins (lactoferrin), inorganic salts and water. The major functions are the protection and the lubrication of the underlying tissue. The saliva, which is produced by the salivary glands, mainly consists of water (up to 99.5%), inorganic salts, proteins, and mucins. The high molecular weight mucin MG1 can bind to the surface of the epithelium and build the so-called mucus layer, displaying the acellular barrier of the oral cavity The mucus of the following parts, stomach and small and large intestine, is mainly produced by intraepithelial cells, and hickness increases from proximal to distal parts of the small and large intestine . Depending on the method used for the determination, the thickness of the mucus layer shows marked variation..The characteristics facilitating the passage through human mucus are relatively well known: electrostatic repulsion from negatively charged sugar moieties favors the penetration of positively charged hydrophilic molecules; the passage of lipophilic compounds is slow. Viruses, like the Norwalk virus with a size of 38 nm and human papilloma virus with a size of 55 nm diffused in human mucus as rapidly as they do in water These findings suggest that the surface charge plays a crucial role in the transport rates of nanoparticles through a mucus layer

In addition to particle size, dose and duration of the exposure are important for the interpretation of the data. In addition to particle size, dose and duration of the exposure are important. There is  a size-dependent decrease of the uptake from 34% for 50 nm particles to 26% for 100 nm particles , and dose and duration of the exposure are also important for absorption and uptake of NM.

Changes in mucus composition induced by Ag nanoparticles (Jeong et al., 2010), polystyrene particles and diesel exhaust increased mucus permeability and permeation of small molecules by a factor of 5. Thus NM enter more quickly through disease barriers.

The adherence of polystyrene nanoparticles to inflamed colonic mucosa was much higher than to normal mucosa. Inflammation appears to increase uptake and permeation of NMs in vitro and in vivo. Inflammation caused by Yersinia pseudotuberculosis increases the uptake of 100 nm carboxyl polystyrene particles in cell monolayers and in intestinal biopsies. Other factors of absorption include pH and thickness of the mucus layer, the gastrointestinal flora and in gastrointestinal passage time (motility)

Whereas plasma membranes restrict the cellular access for metal ions like silver cations, silver nanoparticles were readily internalized and intracellular silver concentrations were much higher than for silver ions. Studies for uptake and toxicity should, therefore, include AgNO3 for silver nanoparticles (Trojan horse effect) or bulk material.. Absorption may also be altered by a changed metabolization by enterocytes. Polystyrene and silver particles have been shown to inhibit the activity of cytochrome P450 enzymes, of note

To avoid foods rich in titanium oxide nanoparticles you should avoid processed foods, and especially candy. This information may make one question if these NM have any impact on the surge of colitis seen ion the general poplulation? How about autoimmune diseases? How about general inflammation, for if NM damage the intestinal barrier, inflammation results and it’s attendant consequences.

Azocarbonamide and Food – more environmental pollutants

Azodicarbonamide (AZA)  is a low molecular weight foaming agent used in plastics, rubbers, and as an oxidizer in flour to give it texture. The chemical is a condensed version of hydrazine and urea (H2N-OC-N=N-CO-NH2) which allows modification of other products by high expansion and self-dispersion of this chemical to create foaming.  In it’s use for food as a  dough conditioner, it has a volume/texture effect on the finished loaf, serving as a functional ingredient to improve the ‘quality’ of the bread.  Per the FDA, if the amount of ADA  is more than 45 ppm (.0045%) then the presence of ADA must be on the label. Other approved oxidizers include potassium bromate, calcium bromate, potassium iodate, calcium iodate and calcium peroxide. The  maximum use levels of these other oxidizers are  75 ppm based on flour. Also permitted are dehydro-L-ascorbic acid, added in the form of ascorbic acid at an unrestricted level. This is what is used in Europe to add quality to the dough.

Historically the use of oxidizers resulted from changes in the way wheat flour is shipped to factories. In the past, wheat flour would oxidize naturally over the long times spent in shipment to the factories, however, with more secure means of shipment (sealed bins, bulk tank trucks, and multiwall paper sacks) flour arrives at bakeries faster and ‘greener’ with less oxidization of the flour. Oxidized flour produces better quality breads. Holding bread for fermentation to oxidize in the bakeries is uneconomical and hence the use of oxidizer, such as ADA. The use of ADA shortens the required fermentation time and produces bread with a finer cell structure, which makes the crumb appear whiter. Bread made with ADA has a higher volume, finer grain, thinner cell walls and softer texture, and the dough has better handling characteristics. Concerning the exposure to ADA, it is more likely to occur in the factory workers using the ADA for oxidization. Likewise, as far as semicarbazide, one’s exposure is higher from glass jars with plastic lids

Azodicarbonamide, as a bleaching agent and improving agent, is a permitted food additive in certain countries and it’s presence can be determined by high-performance liquid chromatography. However, it partially degrades with the heat of processing to form trace amounts of semicarbazide, which shows carcinogenicity and also has been shown to cause tumors. It also is associated with cutaneous and pulmonary hypersensitivity.

Assessment of the Determination of Azodicarbonamide and Its Decomposition Product Semicarbazide: Investigation of Variation in Flour and Flour Products

Azodicarbonamide acts as an oxidizer in flour to condition the flour.

Its safety sheet can be found here:

Azodicarbonamide safety Card

Azodicarbonamide has had multiple uses, including as a ‘blowing agent’ in vinyl mats, where at high temperature, it breaks down to form bubbles. Carpet underlays and floor mats are made spongier by this bubble formation. Yoga mats, in particular, gained fame from containing this chemical. The Yoga Mat Chemical CNN

At one point, Azodicarbonamide (ADA) was being investigated to treat HIV virus: Phase I/II dose escalation and randomized withdrawal study with add-on azodicarbonamide in patients failing on current antiretroviral therapy In addition, ADA had synergy with cyclosporine to suppress T cell function: Azodicarbonamide as a new T cell immunosuppressant: synergy with cyclosporin A. Tassignon J, Vandevelde M, Goldman M – Clin. Immunol. – July 1, 2001; 100 (1); 24-30     Also noted in that ADA inhibits T cell responses:Azodicarbonamide inhibits T-cell responses in vitro and in vivo  and that it had some effect in HIV as well:Azodicarbonamide inhibits HIV-1 replication by targeting the nucleocapsid protein

Unfortunately, breakdown products of ADA are carcinogenic and there is an association of ADA with occupational asthma:Kim C, Cho J, Leem J, Ryu J, Lee H, Hong Y. Occupational asthma due to azodicarbonamide. Yonsei Med J. 2004; 45-2: 325-329.

Azodicarbonamide is readily converted to biurea, the only breakdown product identified, and it is likely that systemic exposure is principally to this derivative rather than to the parent compound.  Elimination of absorbed azodicarbonamide/biurea is rapid, occurring predominantly via the urine, and there is very little systemic retention of biurea. The chemical appears to be well absorbed by the inhalation and oral routes in rodents. From the WHO summary regarding ADA:

Evidence that azodicarbonamide can induce asthma in humans has been found from bronchial challenge studies with symptomatic individuals and from health evaluations of employees at workplaces where azodicarbonamide is manufactured or used. There are also indications that azodicarbonamide may induce skin sensitization. On the basis that azodicarbonamide is a human asthmagen and that the concentrations required to induce asthma in a non-sensitive individual or to provoke a response in a sensitive individual are unknown, it is concluded that there is a risk to human health under present occupational exposure conditions. The level of risk is uncertain; hence, exposure levels should be reduced as much as possible. The principal end use of azodicarbonamide is as a blowing agent in the rubber and plastics industries. It is used in the expansion of a wide range of polymers, including polyvinyl chloride, polyolefins, and natural and synthetic rubbers. The blowing action occurs when the azodicarbonamide decomposes on heating (process temperatures ~190–230 °C) to yield gases (nitrogen, carbon monoxide, carbon dioxide, and ammonia), solid residues, and sublimated substances. Decomposition accelerators, in the form of metal salts and oxides, may also be added to bring about decomposition at lower temperatures Azodicarbonamide has in the past been used in the United Kingdom and Eire (but not other European Union member states) as a flour improver in the bread-making industry, but this use is no longer permitted. Data have been identified that indicate ethyl carbamate formation in consumer products such as bread and beer following the addition of azodicarbonamideThe effects of long-term exposure to azodicarbonamide have not been well studied, and no conventional carcinogenicity studies are available. The only data come from l- and 2-year studies in which rats and dogs received diets containing various amounts of biurea. In the 1-year study, rats and dogs ate diets containing 5 or 10% biurea (Oser et al., 1965). One high-dose rat died, and body weight gain was slightly depressed in high-dose males. No other signs of toxicity were observed in rats at necropsy. Most dogs from both dose groups died. Necropsy revealed massive, multiple renal calculi, bladder calculi, and chronic pyelonephritis. Azodicarbonamide is mutagenic in vitro, inducing base-pair mutations in bacteria with and without metabolic activation (Pharmakon Research International, 1984a; Mortelmans et al., 1986; Hachiya, 1987)  In contrast, several standard in vitro assays in mammalian cell systems have yielded negative results A number of reports have been published of individual azodicarbonamide workers alleging asthma induced by exposure to azodicarbonamide. The strongest evidence comes from a study of two individuals (one atopic and one non-atopic) who worked at the same plastics factory for about 4 years (Malo et al., 1985; Pineau et al., 1985). Both wereintermittently exposed (1–2 weeks’ duration, 3–4 times per year) to azodicarbonamide at work. A few months after their first encounter with azodicarbonamide, both developed symptoms described as “eye/nose irritation” at work, followed a few hours later by nocturnal asthmatic symptoms. After a 1- month period free from exposure, both subjects underwent lung provocation studies. Baseline values for forced expiratory volume in 1 s (FEV1 ), forced vital capacity (FVC), and the concentration of histamine required to produce a 20% drop in FEV1 (PC20H) were obtained by spirometry. The link to the WHO paper is here:WHO statement regarding Azodicarbonamide

Occupational asthma caused by a plastics blowing agent, azodicarbonamide

Occupational Asthma due to Azodicarbonamide

PDF version Occupational asthma due to Azocarbonamide

A link to contact dermatitis due to ADA is found here: Azodicarbonamide and cutaneous sensitization

ADA is used widely – link to Natural News issue

Environmental Working Group release on products with ADA

Assessment of the determination of azodicarbonamide and its decomposition product semicarbazide: investigation of variation in flour and flour products. Ye J, Wang XH, Sang YX, Liu Q – J. Agric. Food Chem. – September 14, 2011; 59 (17); 9313-8 : Abstract is below: 

Azodicarbonamide, as a bleaching agent and improving agent, is a permitted food additive in certain countries and can be determined by high-performance liquid chromatography. However, it partially degrades with the heat of processing to form trace amounts of semicarbazide, which shows carcinogenicity and also has been shown to cause tumors. The concentration of semicarbazide in azodicarbonamide-treated flour was determined by isotope dilution ((13)C, (15)N(2)-semicarbazide) liquid chromatography electrospray tandem mass spectrometry (LC-MS/MS). The quantification was obtained utilizing the homologous internal standard. The limits of detection were 1 mg/kg for azodicarbonamide and 0.5 × 10(-3) mg/kg for semicarbazide. The rates of recovery were 82.3-103.1% for azodicarbonamide and 72.4-116.5% for semicarbazide. This study prepared four different types of flour products to investigate the variation of semicarbazide. The concentration of semicarbazide in all types of flour products is higher than that in flour, and the concentration of semicarbazide in outside of flour products is slightly higher than that in the inside. As the problem of food safety hazard aggravates daily, we should be more concerned about food security and human health.


Recently, subway announced the removal of ADA from it’s bread products. Again, why use an oxidizer like this with risks when there are better alternatives?