Review Is Mercury Global a Scam or Should I Invest

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Is a HYIP Scam? | MUST READ 2020 Reviews

Is Mercury Global a Scam? After weighing much consumer feedback, the verdict regarding Mercury is NOT GOOD!

Mercury Global, hosted at, is a shady online investment program that could be fleecing hard-working consumers out of their money.

To find out more regarding this vague investment venture AND why you should AVOID Mercury Global, we invite you to read our unbiased and factual review.

What is

Mercury Global is presented as a professional online investment opportunity that will deliver a stable financial flow while ensuring investors that they can secure ‘financial security’ by being the “owner of the capital and high-yielding assets that generate constantly growing passive income.”

According to, Mercury Global project consists of ‘numerous socio-socio-economic programs that cover all spheres of modern human life.’

Project expects help each participant to shape an individual financial development plan tiered toward their overall investment objectives.

Allegedly, their platform is a top leader in providing high-class professional investment options to achieve wealth and financial freedom.

Who is Behind Mercury Global? does not share any information regarding the owners or current operators behind Mercury Global.

There are not About Us, Contact Us, Terms of Service or Privacy Policy pages visible at

For an online investment opportunity rendering ‘high-class professional’ investment options one would expect one way to touch base with the operators behind Mercury Global.

Instead, we are confronted with a blatant lack of ownership information.

No physical address, reference to a corporate entity or company number or something as minor as a telephone number cannot even be found.

For an online investment opportunity to provide some of the best investment ventures while allegedly having serviced more than 500,000 people not to have viable means of contact or identifying information is suspicious, to say the least. Reviews is not a new domain, WHOIS reports state that became incepted back in early 2020.

However, it wasn’t until the past 6 months that Mercury Global started to make some waves within the online investment community.

According to a thread found at BitcoinTalk:

“Mercury Global is an open international online community of people, based on mutual trust and advanced blockchain technologies, provides to each ach participant the opportunity to create a basic cash flow, to reach the level of prosperity and to sustain it. Community has about 1 000 000 participants around the world and successfully operates for 5 years…”

It is clear that the thread regarding Mercury is heavily looted with affiliated banners but it provides much more insight into Mercury Global than what is shared at

Such as how allegedly investors receive returns up to 1.15% daily during every 300 days while the only supported currencies would be USD, EUR, Bitcoin, Ethereum and Litecoin.

Supposedly withdrawals are executed instantaneously on a weekly occurrence while their investment packages offer returns between 0.7% to 1.15% daily with reposts ranging between $500 to $50,000.

Depending upon which type of currency you invest with, along with the sum, will determine your approximate return.

Feedback early on in the BitcoinTalk thread appeared positive and encouraging, but over the past half year it has turned negative with many members stating that Mercury Global is likely a pyramid or Ponzi scheme.

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“It looks like a pyramid, such an income is too high, the project will not live long, not enough money.”

“It’s one of those slowburn scams that seem to be a particular favorite in Russia, home of the HYIP.”

A question submitted to Quora also came up regarding whether or not Mercury was a Ponzi Scheme.

The answer went on to state that yes, it appeared to likely be a Ponzi scheme. Background was registered on January 8th, 2020 through the registrar.

The registrars tech contact information is as followed:

Francisco Fuentealba
222 Grace Church St. Suite 302,
New York, NY 10573, US
Email: [email protected]

Given the registrar information, it appears that the site was privately registered by a member of

According to SimilarWeb, reflected a global rank of 49,081 with an Ukraine rank of 1,871 as of March 10th, 2020.

From January 2020 to February 2020, suffered a 46.57% decrease in total site visits, which could indicate that the negative user experiences coming to light could being taking their toll against Mercury Global.

Is Mercury Global Trustworthy?

Mercury Global is a unique investment opportunity that appeared to be community operated, making liability and responsibility for security of funds a potential issue for potential investors.

Given the fact that most entities need to be regulated and licensed in order to render investment advice, the question of whether or not Mercury Global is a legally allowed to render investment advice depends upon the laws of where you reside.

Due to the excessive number of negative reviews regarding, we do not believe them to be trustworthy.

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Mercury is an interesting investment opportunity that has caught the attention of many day traders and online investors.

Supposedly being community operated, Mercury Global does not provide much information of value on their site regarding what their venture is about.

We found out more in a single affiliate thread post regrading Mercury Global than we could find on their site, while their promoted ROIs within their platform are HIGHLY unrealistic.

Furthermore, if your investment into Mercury Global proved to be unfruitful, would could you hold liable for your losses when you were promised returns between 0.7% to 1.15% daily?

There are several questions that need to be answered before investors seriously consider Mercury Global as a viable investment route.

Given their wide number of negative reviews, along with the general consensus that Mercury Global is a Ponzi scheme amongst users in the community, we believe that the verdict regarding Mercury Global is straightforward.

Verdict: Mercury Global is NOT Trustworthy!

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We invite you to share your insight, feedback and experiences below.

How to tell if a survey company is a scam or legit

Jim Wang
Updated January 18, 2020
Some links below are from our sponsors. Here’s how we make money.

The idea of earning money from survey sites and market research is really appealing.

What’s not to love about getting asked a few questions and being paid to give answers?

We know companies need to run focus groups. We know they need to test new products, new services, and new ideas like advertisements. As potential customers, our opinion matters.

But like anything else great in this world, there are thieves and scammers lurking around the corner ready to take advantage of unsuspecting people.

Ten years ago, most survey companies were clearly scams. Market research companies just weren’t looking online to pad their survey pools. Nowadays, many market research companies are using the internet to get more responses. The legitimate companies are drowning out the scams, but the scams still exist. And the scammers now have models to copy so they look like legit companies!

The end result is that it’s becoming increasingly hard to tell the difference between a legitimate opportunity and a scam.

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Today, we’re going to teach you how to tell the difference.

In This Article:

What’s a scam?

There are two types of scammy survey sites:

  1. Sites that just pitch you other products and services.
  2. Sites that make you pay to get surveys.

They lure you in with the promise of untold riches through market research but bait and switch it on you. In the first case, they make money off you when you sign up for other products or serices. In the second case, they get you to pay them.

The ones that make you pay to join are similar to the old “work at home” scams. Work at home scams are simple, the promise of “work” if you buy their “startup” package. Replace “work” with surveys and “startup” with membership fees and you have an old scam with a new facade.

In both cases, the companies will also take advantage of the juicy personal information you may have provided. To give you an idea of what happens, I defer to Troy Hunt, a security professional I last mentioned in “Why I Have a Secret Classified Email Address;” his post on how your data is used by giveaway sites (think of those “win a free iPad!” email submission sites) is must-read.

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How the Legitimate Survey Business Works

Before we get into how to determine if a survey opportunity is a scam, we need to understand how the legitimate market research business works.

A big well-known company (like a brand name consumer goods company) needs to do some market research or run a focus group. Both are expensive to do in person, as focus groups often pay $100+ for 60-90 minutes of work to a participant. You can only imagine how much the research company adds to the bill. Online surveys are much cheaper!

So those big companies hire a market research company to send out online surveys to folks with the right demographic target (age, income, marital status, geographic region, etc.). You have survey companies with enough business to run their own (Survey Junkie, Swagbucks, etc.) and you have smaller companies who are there to fill in the gaps.

These second tier companies are often the ones you see listed all over the internet.

In some cases, the survey company only does surveys. These purists are often the closest to the market research companies. In others, there are a lot of other “point earning” activities you can do like “read email” or “watch videos” or “play games.” (more on this later)

I’ve been doing surveys for about six months from a variety of vetted companies and you start seeing the same names – Qualtrics, (Federated Sample) – those are the main guys.

The tough part about market research is that it’s an unpredictable business. It’s unpredictable for the survey taker (you) because companies won’t always want your opinion.

The result is that you get surveys irregularly but you earn a little cash along the way.

You won’t feed your family with surveys but it can earn you a little extra to help pay bills and get further ahead financially.

How the Scam Survey Business Works

The problem is that scam survey companies will prey on that trickle of money and suggest that they can send you a flood. They can’t. They make those promises so you’ll sign up.

Then what happens? They try to make money off you directly, rather than make money from market research companies by having you respond to surveys.

How do they make money off you? They send you offers, like entries into sweepstakes (enter your zip code and email for a chance to win a $500 Apples iTunes gift card!) or other scammier survey sites.

They’ll send you offers of free samples or some other bribe to get you to enter in an email. All the while, earning about $1-3 per sign up (that’s about the going rate for a double opt in email address).

The distinct difference between the two is that scam survey companies will often inundate you with offers immediately upon signup and without any suggestion that you’ll get anything out of it. Legitimate companies set it up like a cashback or pointback scenario, sign up for this offer and get 500 points or $5, thus cutting you in on the commission they earn. You still need to do your research though, which I’ll get into shortly.

For a scam survey business, you are the product.

Beware Impersonators

Recently, I’ve been asked by many readers if Company X or Company Y is legitimate.

In many of those cases, the name of the company was legitimate. The person they were talking to or emailing with was not.

The scammer was pretending to be working at a legitimate survey company!

Identifying this is very hard but if you’re asking questions, that’s a good thing. Call the company and find out if that person is real and works for them. I discovered this type of scam after a reader, Casey, asked me about Taylor Research company in the comments below.

Someone pretending to be from Taylor emailed him from a GMail account, which set off alarms for Casey (good!). When he called Taylor Research, who is very real and respected, he discovered that everything was real except the person who contacted him and the number he was supposed to call. He was the 3rd person to report it and the police are investigating.

Trust your gut!

Who Can You Trust? (besides your gut)

It’s hard to know who to trust before you sign up but I always look at the Better Business Bureau and see what their rating is, whether they have complaints, and what those complaints are about. One of the more popular sites, Swagbucks, has an A+ and 114 closed complaints in the last 3 years. 114 sounds like a lot but when you consider how many members it has and the time frame,

3 a month is a low number.

Here are five survey companies I’ve signed up for and can confirm don’t have any of the flags listed below.

Then start looking for these red flags:

  • Never pay to join – Huge red flag, you should never be paying to join… legitimate companies spend a lot of money building their rosters because the more people they have, the more likely they can fill in those demographic gaps. They would never ask you to pay to join.
  • Never give social security number, credit card information, or full address – There’s really no need for any of that information. The most a company should ask for is general demographic information (age, sex, zip code, income, family, etc.), they don’t need your full address and certainly not your social security number.
  • If they force you to go through promotional offers before they show you anything – Some companies have added these other pieces, like watching movies and playing games, to the core survey offering. The reality is they only get so many surveys so to keep you an active member, they offer these others pieces. They don’t make you wade through offers to get to surveys.
  • Look for a privacy policy – Legitimate companies will always have a privacy policy and it will be prominently linked on their site, often in the footer. If it’s hard to find, I’d move on.
  • They email you from an anonymous account – A legitimate company won’t be emailing you from a or or some other free email service. They will have their own business website with their own email address, like
  • Never take a big payment of any kind where you have to pay some of it back – A common scam is for someone to send you a big check and have you send them something back of value, either money or an expensive product. It’s known as advance fee fraud and the check will bounce (after spending a few days looking like it’s successfully cashed) after a few days, once you’ve already sent back money or items. Never do this.
  • If it sounds too good… – The language companies use can tell you a lot about them. Scams will promise you hundreds or thousands of dollars a month or extremely high payouts on surveys. Your internal BS detector is very good, if you sense something is off then walk away.

Here’s a survey site I find suspicious…

Here’s the homepage… at first, nothing looks suspicious about this company.

When you click on Get Started, the green box is replaced with a “letter” from “Patricia Johnson” with a form at the bottom for name and email. When you enter your name and email, you are sent to this screen where you watch a short video.

The video explains how “Kevin” makes hundreds or thousands of dollars making money sharing his opinion, from the comfort of his own home. The video explains how market research works, like I did in the paragraph above, and is completely accurate. The only complaint I have about the video is that it oversells how much these surveys pay and how much you can earn.

Watch long enough… and then this appears:

And that, my friends, is why I would never sign up for this site. They want you to pay for membership. Biggest red flag of them all.

The tricky part is that it’s hard to know before you sign up! You might be tempted, after putting in your information and watching a video, to give it a try. What’s the worst that can happen right?

Will you earn hundreds and thousands of dollars? Maybe.

Is it worth it? Maybe.

Would it shock you to know that this company is willing to pay a $26 commission for each person that signs up? ��

Final quick tips…

Here are some other ideas that can help:

  • Always use a separate “survey only” email address – Some companies pay you to “read email” (which is code for they’ll email you advertisements) and it can be a lot of email. Plus, if you end up accidentally signing up for a scam, you don’t trash your regular email address.
  • Set up a junk “tester” email address – If you are really worried, you can always set up a junk mail only “tester” email address (I have a gmail account I never check, specifically for this) to run through the sign up process once, just to make sure. Sometimes you can get away with using a temporary disposable email, like the ones offered through Guerrilla Mail, but sometimes sites will not allow you to sign up with a disposable email address.
  • Check the BBB – If the name is extremely generic with lots of dashes, it’ll be hard to find their company name. This itself is a bit of a red flag because most of the legitimate companies have real names to help with the branding. The ones with generic words don’t want to stand out! For legitimate companies, it should be easy to find them on the Better Business Bureau.
  • Check if they are affiliated with CASRO – The CASRO (Council of American Survey Research Organizations) is the leading market and survey research organization.

If you find a survey company and aren’t really sure whether they’re legit, you can always email me and I can take a look. I can even be your guinea pig and sign up first. ��

Just send me an email with the name of the company and I’ll take a peek.

List of Legit Survey Sites

This list includes the legitimate survey sites I know. If the company you’re wondering about is on this list, you can be reasonably assured they’re legitimate at the time of this writing. If they aren’t on the list, they could still be legitimate just smaller (so I don’t know about them). I just can’t say either way. All these companies are on my list of ways to make money.

If you want to share an experience (good or bad) you had with a market research company, let us know in the comments.

About Jim Wang

Jim Wang is a thirty-something father of three who is a contributor to Forbes and Vanguard’s Blog. He has also been fortunate to have appeared in the New York Times, Baltimore Sun, Entrepreneur, and Marketplace Money.

Jim has a B.S. in Computer Science and Economics from Carnegie Mellon University, an M.S. in Information Technology – Software Engineering from Carnegie Mellon University, as well as a Masters in Business Administration from Johns Hopkins University. His approach to personal finance is that of an engineer, breaking down complex subjects into bite-sized easily understood concepts that you can use in your daily life.

One of his favorite tools (here’s my treasure chest of tools,, everything I use) is Personal Capital, which enables him to manage his finances in just 15-minutes each month. They also offer financial planning, such as a Retirement Planning Tool that can tell you if you’re on track to retire when you want. It’s free.

He is also diversifying his investment portfolio by adding a little bit of real estate. But not rental homes, because he doesn’t want a second job, it’s diversified small investments in Fundrise and a farm in Illinois via AcreTrader.


Интегральная финансовая платформа

Комплекс инновационных инструментов, с помощью которых каждый участник получает возможность создать стабильный финансовый поток, выйти на уровень достатка, обеспечить абсолютную финансовую безопасность себе и своей семье, а также перейти в совершенно новый общественный статус рантье — владельца капитала и высокодоходных активов, генерирующих постоянно растущий пассивный доход.


Главный принцип проекта Mercury Global — это всеобъемлющее доверие друг к другу, которое, вот уже на протяжении более 5 лет, является основой построения взаимоотношений между всеми участниками проекта, а также ключевым фактором успеха в достижении ими личных и совместных целей. Именно благодаря взаимному доверию наши участники живут в достатке и процветании.

О нас


Mercury Global принимает в управление свободные средства участников и перераспределяет их, используя уникальную формулу.

Проект состоит из многочисленных социально-экономических программ, которые охватывают все сферы жизни современного человека.

Эксперты проекта помогают каждому участнику разработать индивидуальный план финансового развития и выбрать те программы, в рамках которых участник наиболее эффективно реализует свой план и выйдет на новый уровень финансового благосостояния.


Во главе проекта стоят лучшие представители направления финансовый консалтинг — высококлассные профессионалы мирового уровня, которые благодаря уникальным навыкам и многолетнему практическому опыту, помогли достичь достатка и финансовой свободы сотням тысяч людей по всему миру.

Левченко Ирина

Разрешите себе жить! Жить! Чудить! Творить! Любить! И будьте счастливы!

Андреева Наталья

Поражение? Я не понимаю значения этого слова. Замечательное чувство — знать, что ты сам строишь мир!

Куруч Ярослав

Моя задача в том, чтобы было больше лидеров, а не в том, чтобы было больше тех, кто следует за мной.

Штанько Людмила

Все удивительное всегда со мной!

Хоптинец Вера

Главное в жизни — найти себя, свое и своих!

Владимир Гученко

Запомни друг, что жизнь – прекрасна!
И сколько б не было в ней зла,
Не обижай людей напрасно!
Расти свой Разум для добра.

Людмила Неживенко

Это так классно – быть полезной людям и ощущать их поддержку!

Юлия Якуня

Окружай себя только теми людьми, кто будет тянуть тебя выше!

Валентин Майстус

Одни из главных законов мироздания – это Любовь, Созидание и Благодарность! Пользуйтесь ими и у Вас все непременно получится!

Сергей Белоусов

Я обожаю делиться опытом и знаниями со своей командой!

Наталья Радова

Берите ответственность за свою жизнь и за свой финансовый доход!

Галина Денисенко

Если хочешь идти быстро – иди один.
Если хочешь идти далеко и быть в достатке – идем вместе в нами!

Вячеслав Абрамович

Относись к человеку так, как хотел бы, чтобы он относился к тебе!

Руслан Скороход

Давайте строить вместе.

Как стать


Mercury Global — это главный проект Сообщества Меркурий — всемирного сообщества свободомыслящих людей. Основанное в январе 2020 года, на сегодняшний день Сообщество Меркурий насчитывает более 500 000 человек из более чем 50 стран мира. Внутри Сообщества, благодаря взаимному доверию и объединению ресурсов и

усилий всех участников, разработаны и успешно развиваются уникальные проекты, направленные на полное удовлетворение всего спектра человеческих потребностей, создание благоприятной среды для всестороннего развития личности, а также на построение нового типа общественных взаимоотношений — коллективной гармонии.


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The Clinical Importance of the Mercury Problem in Artisanal Small-Scale Gold Mining

Justice Afrifa

1 Department of Medical Laboratory Science, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana

2 Scientific Research Center, Second Affiliated Hospital of Harbin Medical University, Harbin, China

Yeboah Kwaku Opoku

3 Department of Biomedical Science, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana

4 Biopharmaceutical Laboratory, College of Life Sciences, Northeast Agricultural University, Harbin, China

Eric Ofori Gyamerah

5 Department of Biochemistry, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana

George Ashiagbor

6 Department of Wildlife and Range Management, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Rosemary Doe Sorkpor

7 Food and Drugs Authority, Cape Coast, Ghana


Artisanal small-scale mining is widely operated in various countries serving as a livelihood to many rural communities. However, it is a significant source of environmental mercury contamination which affects human health. Amalgamation and amalgam smelting, two significant steps in the artisanal small-scale mining operations generate lots of mercury vapors, leading to chronic exposure among miners. Thus, this article seeks to provide a topical review of recent findings on organ damage and metabolic disorders among mercury-exposed artisanal small-scale miners with emphasis on the contributing factors such as personal protective equipment usage and artisanal small-scale gold mining-specific occupational activities. Also, insights into the effect of mercury intoxication and mechanisms of action on organ and metabolic systems among exposed individuals are provided.


Artisanal or small-scale gold mining (ASGM) is usually characterized by the use of rudimentary or basic tools operating at a limited level of production with reduced capital investment. According to the International Labor Organization, ASGM operations are labor intensive, employing low, and basic level mechanization (1). In most instances, poverty is an influential primary drive in ASGM activities thus providing a source of livelihood for many rural communities (2, 3). The economic importance of ASGM cannot be overemphasized, hence the extensive coverage of its operation spanning over 55 countries across Asia, South America, and Africa (4). It is reported that direct or indirect dependency on ASGM for livelihood exceeds 100 million persons globally (5). Besides these essential microeconomic effects, other adverse environmental and health impacts are associated with ASGM. Numerous studies have reported on the contributions of ASGM to land degradation (6), and water pollution (7–9), as well as associated social problems (10). The incidence of increased social aggression and violence between resident miners and new settlers or larger mining companies have been reported (11). Irrespective of these issues, it appears that strict regulations needed to streamline the activities and operations of ASGM are not adequate and sometimes fails to protect the natural ecosystems of the affected areas (9).

Of particular concern in AGSM is what is described as the “mercury problem” and its clinical implications on human health. As much as ASGM provides a livelihood to many rural communities, it is also responsible for the world’s fastest emerging source of mercury contamination (2, 3). Usually, the type of mining procedure employed by miners of various precious minerals on a small scale is mainly dependent on the characteristics of the mining site and the type of mineral involved. In ASGM, gold amalgamation with mercury has been a critical component in the extraction process (12). Global estimation of the release of airborne elemental mercury attributed to inappropriate mining practices is about 400 tons (13). The WHO reports implicated the inhalation of a vaporized form of elemental mercury during amalgam smelting as the main route of exposure (14). However, exposure through other routes including oral and dermal is also possible (15). Mercury toxicity is known to be insidious, hence the transition from acute to chronic exposure may be silent. Trends in current studies point to increasing disruption of organ and metabolic functions among artisanal small-scale miners (ASGMs) as a result of mercury exposure. It is therefore vital that various clinical implications of mercury exposure and the associated damaging effects among ASGMs received the necessary attention. Thus, this article seeks to provide a literature review of the recent findings on the contribution of mercury exposure to organ and metabolic disorders among ASGMs with emphasis on contributing factors such as personal protective equipment (PPE) usage and ASGM-specific occupational activities. In addition, we provide insight into the effect of mercury intoxication and mechanisms of action on organ and metabolic systems among exposed individuals. Relevant documents pertaining to the topic under discussion were extracted from Web of Science, Pubmed, and Google scholar. However, relevant studies that assess specific clinical biomarkers among ASGMs are shown in Table 1 .

Table 1

Health implications of mercury exposure to ASGMs.

Clinical outcome Effects References Year Country
Neurologic effects Increased mercury levels in urine and hair Bose-O’Reilly et al. (16) 2020 Indonesia
Peplow and Augustine (17) 2020 Surinam
Dolbec et al. (18) 2000 Brazil
Renal abnormalities Reduced eGFR, elevated urine protein Afrifa et al. (19) 2020 Ghana
Increase in proteinuria Ekawanti and Krisnayanti. (20) 2020 Indonesia
Increased proteinuria Franko et al. (21) 2005 Nigeria
Thyroid risks Reduction in total triiodothyronine, free triiodothyronine, and free thyroxine Tayrab (22) 2020 Sudan
Haemato-pathological risk Reduced hemoglobin and hematocrit levels Ekawanti and Krisnayanti (20) 2020 Indonesia
Associated with anemia in children Weinhouse et al. (23) 2020 Peruvian Amazon, Peru
DNA oxidative stress Positive correlation of LINE1 methylation with 8-hydroxy-2-deoxyguanosine(8-297 OHdG) and Hg levels Narváez et al. (24) 2020 Colombia
Alterations in membrane permeability, changes in macromolecular structure Flora et al. (25) 2008 India
Genotoxic damage Micronuclei in mouth epithelial cells, nucleoplasmic bridges, gemmation, and binucleation Rosales-Rimache et al. (26) 2020
Immunological response High ANA and ANoA, increased titers of ANA and ANoA, higher levels of proinflammatory cytokines IL-1β, TNF-α, and IFN-γ Gardner et al. (27) 2020 Brazil
Increased pro-inflammatory, anti-inflammatory cytokines, and IL-17 Nyland et al. (28) 2020 Brazil

Mercury Speciation, Toxicity, and the “Mercury Problem” in ASGM

Mercury Speciation and Toxicity

Mercury is an environmental toxin which is widely distributed and has been at the center of recent public health discussions due to the severity of its impact on human health systems. Physiologically, mercury seems to have no known beneficial health effect, even though an average man weighing 70 kg is reported to accumulate about 13 mg of it (29). Beside the immunotoxic effect, the level of toxicity is such that it affects all manner of persons and even low exposure levels are known to cause toxicities to the cardiovascular, reproductive, developmental, renal, and central nervous systems (CNS). Mercury poisoning and severity depends on the chemical state of the mercury which determines the route of exposure. The environmental distributions are in three forms(elemental, organic, and inorganic), and each is characterized by specific chemical reactions, solubility, and toxicity (30). Elemental mercury, also known as quicksilver, is liquid at room temperature and is poorly absorbed in the gastrointestinal tract (GIT) rendering it less toxic in this form and hence quickly eliminated through fecal matter upon ingestion. However, when volatilized into a vapor, it is well-absorbed through the lungs (31). Mercury vapor, when inhaled, could quickly enter the circulatory system via the pulmonary alveolar membranes and invade the CNS, blood cells, and the kidneys where it can be partially converted to HgCl2 and retained for years (32). Elemental mercury exposure is monitored through the measurement of urine mercury. Chronic intoxication could exhibit a myriad of symptoms ranging from polyuria, and proteinuria to nephritic syndromes in severe cases accompanied with hematuria and anuria (33).

Organic mercury in the form of methyl, ethyl or phenylmercury is usually formed through the biomethylation of mercuric compounds by aquatic microorganisms and eventually released into the environment. Among the various forms, methylmercury seems to be the most toxic with extensive bioaccumulation along the sequential order through the aquatic food chain. Substantial accumulation is observed in highest order fish predators and other fish consuming marine mammals. According to the committee on environmental studies and toxicology of the national research council in the year 2000, consumption of fish contaminated with mercury had led to a lot of public health concerns such as neurotoxicity (34). Unlike elemental mercury, up to about 95% of methylmercury is absorbed by the GIT into the red blood cells and the brain through a covalent bond with glutathione and cysteine protein groups (35) The level of blood mercury is an indicator of total mercury, which is made up of both elemental and methylmercury. However, methylmercury usually constitutes a significantly higher percentage of total blood mercury. Nonetheless, there is evidence to show that both inorganic and organic forms of mercury could be predicted from total blood mercury (36). For non-fish-eating people, the International Union of Pure and Applied Chemistry (IUPAC), in collaboration with the International Commission on Occupational Health (ICOH), set the maximum limit of blood mercury concentration at 2 ug/l (37). People intoxicated with methylmercury could exhibit symptoms such as ataxia, peripheral neuropathy, choreoathetosis, visual loss, confusion, and coma (38).

Inorganic mercury, usually referred to as mercury salts, are useful for several products including medicines, explosive detonators, and mercuric fulminates (39). However, it could have very deleterious effects on human health upon exposure. There is evidence to show that, elemental mercury could be converted into other forms or combine with Sulfur compounds in vivo (40, 41). Also, compounds containing both organic and elemental mercury could be oxidized to the inorganic forms resulting in the production of hydroxyl radicals (42). Mercurial is excreted through the fecal matter hence their negligible excretion from the urine leading to reduced levels (about 10%) of total excretion (30). However, in the state of chronic exposure, there is an increase in excretion levels (43). The ability of inorganic mercury compounds to bond with sulfhydryl (-SH) groups and the degree of its solubility determines its degree of toxicity. Mercury salts primarily target the kidneys leading to acute tubular necrosis, nephrotic syndrome, and general renal injuries. Chronic exposure could also cause permanent damage to the CNS.

Mercury Use and Exposure Among ASGM

ASGM is a long-standing operation with the main focus to extract gold from sediments or rocks. However, operators usually work on secondary or tertiary alluvial ores located in river sediments. This is achieved by panning, dredging, or hosting sediments down river banks or open pits by the use of high-pressure pumps. Briefly, the process of ASGM involves a series of steps including extraction of ore from the soil, crushing of the ore using rudimentary tools, milling of the ore into fine powder, concentration and washing in sluices and pans, panning, amalgamation to capture the gold and lastly burning the amalgam to recover the gold. For the purpose and objectives of this review, we focus on the processes that employ the use of mercury which may lead to occupational exposure.

In most ASGM, mercury is used in the amalgamation process, and the amount of environmental emission depends on the method employed. In whole ore amalgamation, there is enormous environmental emission of mercury as opposed to the gravity amalgamation method. In either method, mercury is emitted into the environment from the disposal of mercury-laced tailings and process water into water bodies and underground vicinities coupled with atmospheric emission of mercury vapor from the smelting process (9). It is estimated that for every gram of gold produced by amalgamation, 1 or 2 grams of metallic mercury is lost (44).

Occupational and general population exposure to mercury can be direct and indirect. Direct exposure is chiefly attributed to the presence of elemental mercury (Hg) vapors in ambient air. Notwithstanding, the inhalation of mercury vapor in workplace atmospheres is the main route of occupational exposure which is often severe and acute with up to 80% absorption by the lungs during high exposure (45). The major organs damaged are mostly the kidneys and lungs, but there can also be damage to the nervous system. According to the WHO, indirect exposure, however, occurs as a result of the presence of elemental mercury vapor (Hg) contaminating surrounding surfaces, getting into water bodies, fishes, foodstuffs, etc. (46). The primary and major sources of all non-occupational exposures are through dietary intake of contaminated fishes and seafood (47). Heating of mercury amalgam also unleashes mercury vapors into the atmosphere which are deposited on walls, clothes and other surrounding surfaces leading to environmental contamination. Contact with any of these contaminated objects even after burning the amalgam could lead to inhalation of the fumes. The effect of mercury exposure is not limited to the ASGMs but also the surrounding communities, as the vapors are blown by the wind to nearby surroundings.

Specific Occupational Activity and PPE Non-Compliance Among Mercury-Exposed ASGMs

In a high mercury polluted environment, the use of PPE should be strictly adhered to mitigate the personal exposure level. However, reports among ASGMs reveal an insignificant to a non-existent PPE compliance. For instance, among ASGMs in Ghana, Afrifa et al. found that about 86.55% of their study participants exhibited absolute non-compliance for appropriate use of protective clothing or equipment. Specifically, 89.8% non-compliance in the use of nose mask for protection against vaporous mercury was reported (19). These findings are similar to those of earlier studies which reported limited use of PPE among ASGMs (3). (48) confirms that, among a group of Tanzanian ASGM population, miners and millers were directly exposed to mercury during both amalgamations and burning without retorts (a device that collects mercury during amalgam burning) (48). This trend seems to be widely spread across the ASGM communities around the world as Rojas et al. (49) also found about 55.5% of absolute PPE non-compliance among gold workers near El Callao, Venezuela. The high non-compliance with PPE use has been attributed to the low level of formal education as well as lack of training in mercury toxicity and management processes among ASGMs. Interestingly, there seems to be a reluctance among ASGMs to employ the use of a retort which could provide a medium to reduce exposure to vaporous mercury. Even though it is less expensive, easy to use, and globally recommended, non-compliances have been reported in Ghana (3), Mozambique, Ecuador, and Guyana (50).

Among ASGMs the level of mercury exposure and subsequent intoxication is associated with the specific type of job and at which stage of the mining process an individual is engaged in. Again, occupational mercury exposure has been associated with factors such as the type and nature of mercury, the number of years of exposure as well as the physical state of the mercury (51). In its natural state and at room temperature, liquefied mercury, also known as quicksilver, is less toxic when ingested. This is due to the inability of the gastrointestinal tract to readily absorb it, leading to complete excretion in the stool. However, there is conclusive evidence to show that activities that could lead to the generation of vaporous mercury such as the heating and burning of mercury are associated with increased mercury exposure and subsequent intoxication. This assertion is supported by findings from different studies that reported increased mercury exposure among ASGMs that are involved in gold smelting and amalgamation (19, 20). Again, the risk of increased mercury exposure and intoxication has been associated with the duration of work as an artisanal gold miner. Basically, the longer the working period, the higher the risk of exposure. Franko et al. (21) found that among ASGMs at the Idrija mines, the duration for the initiation of clinical symptoms was around 15 years. These findings confirm the insidious onset of clinical symptoms that could result in chronic effects with prolonged exposure to mercury vapor. The negative effect of mercury exposure is buttressed by the low ACGIH TLV-TWA exposure limit of 0.025 mg/m 3 for elemental and inorganic mercury (52) and a BEI of 20 μg Hg/g creatinine for urine mercury (53).

Health Implications of Mercury Exposure to ASGMs

The use of mercury goes back to ancient times with its widespread medicinal applications in the treatment of conditions such as skin diseases and syphilis. However, with the accompanying side effects and recorded deaths, the harmful effects of mercury exposure on health were evident with much research after the 20th century (54). It was then established that although mercury is widely distributed in the environment, it is non-essential and toxic to the human body (55). ASGMs who solely rely on the use of mercury serves as the major source of global mercury pollution (56). Mostly without any PPEs, the isolation of the amalgam is done manually followed by heating with a torch or over a stove to distill the mercury and isolate the gold. This, therefore, presents myriads of health challenges to ASGMs.

Neurotoxic Risk of Mercury-Exposed ASGMs

The adverse health implications of mercury and methylmercury are not immediately noticeable but manifested over time (57), up to about 5 to 10 years after exposure (16). Mercury toxicity has been reported to affect various organs and metabolic functions. The most commonly reported complications of mercury intoxication among workers engaged in ASGM are neurologic effects including tremor, ataxia, memory problems, and vision disorders (57). Among people living in Cisitu, a small-scale gold mining village in Indonesia, Bose-O’Reilly et al. reported severe neurological symptoms and elevated levels of mercury in urine and hair. This was reported to have resulted from possible exposure to inorganic mercury in the air, and the consumption of mercury-contaminated fish and rice (16). Elsewhere among the indigenous Wayana community of Puleowime-Surinam, neurological abnormalities were observed among the mercury-exposed population. The researchers through a battery of neurological tests reported neurotoxic effects which were consistent with methylmercury exposure (17). These findings were consistent with those of previous studies which concluded that neurobehavioral manifestations consisting of subtle neurotoxic effects on motor functions among people living in gold mining areas of the Brazilian Amazon were associated with low-level methylmercury exposure (18). Clinically, several plausible reasons could contribute to the neurodegenerative effect of mercury exposure among these miners. These may include, but are not limited to, the ability of mercury [especially methylmercury (MeHg)] to increase the level of reactive oxygen species. This is evident from the fact that the treatment of mice with methylmercury led to an upsurge in lipid peroxides in the brain, coupled with the inhibition of antioxidant enzymes (58). Methylmercury impedes glutathione reductase (59) and binds directly to selenocysteine residue in glutathione peroxidase (GPx), leading to an increase in hydrogen peroxide levels (60). Again, methylmercury is reportedly involved in the inhibition of thioredoxin and thioredoxin reductase preventing the elimination of ROS (61). Lastly, it is possible for MeHg to impede the structuring of microtubules which are essential for CNS development (62–64). On the other hand, inorganic mercury has been implicated in neuronal hyperpolarization by increasing the permeability of chloride channels of GABAA receptors in the dorsal root ganglion (65).

Hepato-Renal Risk of Mercury-Exposed ASGMs

Besides the central nervous system, the kidneys are easily targeted for mercury toxicity with high accumulation particularly in the areas of the proximal tubules (66). However, the extent of damage and renal dysregulation have been shown to be a function of the duration of exposure, state of the mercury, and the extent of mercury exposure, as well as the exposure route (67). Among small-scale gold miners, renal abnormalities have been expressed in the form of elevated serum creatinine, reduced eGFR and increased proteinuria (68). This was in line with a recent study which reported a significant association of mercury exposure with reduced eGFR, and elevated urine protein among ASGMs in Ghana (19). Similarly, a significant increase in proteinuria has been reported among mine workers in Idrija, Nigeria (21) and Sekotong, West Lambork-Indonesia (20). In contrast, others reported no association of low to moderate mercury levels with renal function biomarkers such as creatinine, albumin, and excretion of β-2 macroglobulin except a significantly reduced eGFR among artisanal gold miners who are exposed to mercury vapor (67). Again, a study that assessed exposure to airborne mercury during gold mining in Venezuela found 7.8% of the participants presenting with a detectable level of urinary N-acetyl-ß-D-glycosaminidase (NAG). They also reported a significant correlation between urine NAG and urine mercury levels among the study participants (69). The advantage of NAG as a renal biomarker is its ability to detect preclinical, non-specific cellular disruption to the proximal tubules of the kidneys. This confirms the insidious nature of mercury toxicity, hence the need for precautionary measures to be adopted by small-scale miners. Within the kidney, the most vulnerable section susceptible to mercury toxicity is the pars recta of the proximal tubules. Experimental studies in animal models have revealed immunologically mediated glomerulonephritis after mercury exposure (70), emphasizing the link between mercury exposure and glomerulonephritis, chronic renal disease, acute tubular necrosis, and nephrotic syndrome (71–73). Studies have also reported various kidney injuries such as tubular dysfunction, increased proteinuria as well as glumerulonecrosis among mercury-exposed workers (74).

Thyroid and Haemato-Pathological Risk of Mercury-Exposed ASGMs

Thyroid hormones critically influence brain development through its involvement in neurogenesis and synaptogenesis with classical function in cellular differentiation, metabolic regulation, growth, reproduction, and mediation of cellular response to stimuli. Among small-scale miners, few studies (22, 75) have assessed the possible relationship between thyroid function and mercury exposure. First, Tayrab reported a significant increase in thyroid stimulating hormone and total thyroxine with a consequent reduction in total triiodothyronine (T3), free triiodothyronine (FT3), and free thyroxine (FT4) irrespective of age and weight among traditional gold miners working in Abuhamed-Sudan (22). Others have reported an association between elevated blood mercury levels and variations in thyroid hormone levels among artisanal small-scale miners in Ghana. The above study also found that increasing blood mercury levels corresponded with a decrease in both FT4 and FT3. However, they reported a normal mean FT3 and FT4 among the miners and, thus, immediate clinical complication was not inferred (75). Again, evidence of T3 reduction in response to mercury exposure has been reported in several studies (76, 77). Mercury can interfere with hormone receptor action, thus contributing to the inhibition of some specific enzymes in the hormonal synthetic pathways with the possibility of endocrine function impairment (78). Findings from the above studies point to a decreased level of T3 among the mercury-exposed groups compared to the unexposed controls. It is possible for mercury to inhibit 5′- thyroxine deiodinase type II, which is critical in the conversion of T4 to T3, by primarily targeting the liver (79). Also, numerous studies (80–82) have provided evidence of deiodinase activity inhibition mediated by mercury exposure in adult rat liver. After inhalation, mercury vapor is rapidly dispersed into the blood with subsequent depositions in organs including brain, kidney, and placenta (21, 55). Also with relative ease, inhaled mercury vapor enters the circulatory system and invade primary red blood cells by crossing the pulmonary alveolar membranes (32). Ekwanti et al. reported a significantly reduced hemoglobin and hematocrit levels among mercury-exposed small-scale miners compared to non-miners and also found a significant correlation between the smoking habits of miners and hemoglobin concentration. However, the seemly abnormal HB levels of the mercury-exposed miners were restored when corrected for smoking (20). Elsewhere, Brandt al. reported a reduction in hematocrit and hemoglobin levels in mercury-exposed mice (83). In a recent study conducted in the Peruvian Amazon, the level of hair methylmercury was associated with anemia in children living close to an ASGM community (23). Further, it has been established that the ability of mercury to compete with iron for binding to hemoglobin results in impaired hemoglobin formation (84).

DNA Oxidative Stress and Genotoxic Risk Among Mercury-Exposed ASGMs

Apart from the regular organ function biomarkers such as thyroid hormones, liver enzymes, and regular renal function markers, other markers have been employed to assess the level of ASGM associated mercury toxicity. Mercury is a known precursor to oxidative stress and mitochondrial functional abnormality (85), and this may result in an alteration in calcium homeostasis that leads to lipid peroxidation. The ability of mercury to also act as a catalyst for Fenton-type reaction promotes the levels of radical oxygen species thus increasing the oxidative stress level (86). In a study that assessed oxidative stress and repetitive element methylation changes in artisanal gold miners occupationally exposed to mercury in Colombia (La Mojana), Narvaez et al., reported a significant association of Long Interspersed Nuclear Element 1 (LINE1) and Alu(Yb8) DNA methylation with gold miners as compared to the control group. Additionally, LINE1 methylation was positively correlated with 8-hydroxy-2-deoxyguanosine(8-OHdG) and Hg levels. (24) These findings emphasize the negative effect of Hg on oxidative stress and DNA methylation in gold miners. Various studies (25, 87, 88) have reported alterations in membrane permeability as well as changes in macromolecular structure due to the high affinity of cellular mercury for sulfhydryl and thiol groups leading to DNA damage. This has been demonstrated by the significant increase in 8-OHdG in the urine of mercury-exposed workers in China (89) similar to that observed by Narvaez and co.

In another study, mercury exposure related to genotoxic damage among small-scale mining workers was reported. Rimache et al. found that as much as 15% of their study population presented micronuclei in mouth epithelial cells. Their results also indicated the presence of other chemical risk genotoxic indicators including nucleoplasmic bridges, gemmation, and binucleation (26).

Immunological Response to Mercury Exposure Among ASGMs

Mercury is an immunotoxin which has been shown to induce an autoimmune response in animal models (90). The immunotoxicity of mercury is characterized by lymphoproliferation, elevated immunoglobulin (IgG and IgE) levels, as well as increased circulating levels of autoantibodies such as anti-nuclear autoantibodies (ANA) and anti-nucleolar autoantibodies, (ANoA) (91). Recent studies among mercury-exposed small-scale miners reveal a higher prevalence of detectable ANA and ANoA and increased titers of ANA and ANoA among mercury-exposed gold miners compared to diamond and emerald miners who are not at risk of occupational mercury exposure. The researchers also identified higher levels of proinflammatory cytokines IL-1β, TNF-α, and IFN-γ in the serum of the mercury-exposed gold miners compared to diamond and emerald miners (27). In line with the above study, Nylander and co also reported an association between elevated blood and plasma mercury with ANA but not with ANoA. However, they found that among persons living in the Lower Tapajós River Basin in the Brazilian Amazon with a history of mercury use in small-scale gold mining, pro-inflammatory, anti-inflammatory cytokines, and IL-17 were increased with MeHg exposure (28). The above studies provide evidence and confirmation of the immunomodulatory effect of mercury exposure among the affected population.

Signs and Symptoms of Mercury Intoxication Among Artisanal Small-Scale Miners

The signs and symptoms of mercury exposure among artisanal small-scale miners have been shown to be a function of the extent and route of exposure (3). The commonly reported symptoms range from hair loss through a persistent headache to skin rashes. Among Ghanaian small-scale miners, itchy eyes, fatigue, skin rashes, red eyes, metallic taste, and complaints of numbness were reported as the predominant complications suggestive of mercury exposure (3, 19). Elsewhere, low-level mercury exposure has been associated with symptomatic central nervous system toxicity in Bornuur and Jargalant soums (92). In Burkina Faso, Tomicic et al. (93) found general complaint of headaches, thoracic pain, dizziness, vision disorder and persistent cough as the most prevalent signs and symptoms among workers who washed ore. They also reported a direct relationship between the task of packaging mercury in small flasks and rhinitis (93). Similarly, fine tremor of the eyelids, fingers, and lips, altered tendon reflexes and dysdiadochokinesis in addition to metallic taste and sleep disturbances were observed among mine workers at Rwamagasa (48).

Conclusion and the Way Forward

Mercury exposure presents myriad of health disorders ranging from neurotoxicity and hepato-renal dysfunction, to thyroid and haemato-pathological disorders of public health concern. This comes about as mercury interferes with the action of some important biological molecules and also causes oxidative stress, leading to these observed health implications. However, the use of PPEs which can reduce the level of exposure to mercury is very limited among ASGMs, leading to excessive exposure. It is, therefore, vital that these miners are encouraged to adhere to the use of PPEs and other safety devices such as retorts which could reduce the level of vaporous mercury exposure. Most importantly, gold mining procedures devoid of mercury use, such as cyanide leaching and floatation techniques to recover gold, should be encouraged and regulated among these workers. Finally, it seems the level of knowledge on the harmful effects and management of mercury among these miners is low. It is, therefore, important that regular training and workshops are organized for these miners to help increase the level of awareness to the inherent dangers of the use of mercury both on human health and the entire ecosystems.

Author Contributions

JA conceived and designed the manuscript, JA, YO, EG, GA, and RS wrote, reviewed and edited the manuscript.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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