What Is Arsenic Poisoning?

Introduction

Arsenic can be a dangerous compound that can cause severe damage and death to anyone exposed to large doses of it. It has a long history as a toxin and a poison, being referenced in Agatha Christie’s mystery novels as well as several poisonings reported until the 1800s. However, arsenic poisoning in the general population is commonly linked with contamination of water and food supplies.¹

Forms of arsenic

Arsenic occurs in many forms, both in an organic and inorganic state. Depending on the chemical composition and form, it can vary in toxicity depending on how it enters the body. There are three common forms of arsenic:

• Organic compounds: Arsenic compounds that contain carbon. These are mostly non-toxic²
• Inorganic compounds: Arsenic compounds that do not contain carbon. These are toxic and known to cause certain cancers
• Gas state

Arsenic trioxide is one of the most toxic and common inorganic forms. It is a white or clear solid at room temperature that looks similar to sugar. It lacks smell and taste, making it difficult to detect. When heated and burned, it will release fumes and convert to a highly toxic gas. 

All sale of arsenic is prohibited in the UK under the Sale of Arsenic Regulation Act passed in 1851.³

Arsenic naturally occurs in its inorganic state in soil and types of rock. Arsenic is commonly found as a result of:

• Volcanic activity: large source of arsenic
• Forest fires
• Breakdown of rocks by natural processes
• Micro-organism activity

The most common cause of arsenic exposure to the general public is through food and water contamination. Arsenic found in soil can contaminate the surrounding water and food supplies. 

Health effects

The effects of arsenic poisoning are heavily dependent on the arsenic dosage, age and health susceptibility of the patient affected. Arsenic exposure through ingestion (eating/drinking) or inhalation, even in low doses, can be highly toxic. 

When ingesting inorganic arsenic, such as arsenic trioxide, the fatal dose is reportedly 1-3 mg/kg; however, survival has been observed at higher doses.

Systemic impact on different organs

Skin and nails

Direct contact with arsenic can cause skin irritation at the point of contact. However, it is not rapidly absorbed through the skin and is unlikely to affect other organs unless the skin is broken. 

Gastrointestinal system

When ingested, arsenic rapidly absorbs into the gastrointestinal system, causing severe disruption. Symptoms vary from nausea, vomiting, and abdominal pain in low doses to significant organ damage or death in high doses.

Nervous system

Inhalation of arsenic gas or arsenic in dust affects the airway and lungs. In severe cases, it can cause haemorrhaging of the trachea or bronchia. In moderate exposure, arsenic may cause:

• Bronchitis
• Rhinitis
• Laryngitis

Long-term health risks

Long-term exposure to inorganic arsenic has many potential long-lasting effects on the body. It has been extensively studied in areas where arsenic is present in high levels from nature.

In the skin, effects include:⁴

• Palmoplantar hyperkeratosis: thickening of the outer skin layer on the palm of the hands and soles of the feet
• Hyperkaratinised warts: thickening of the outer skin layer that results in a hard texturised wart
• Hyperpigmentation: darkening of the skin in certain areas

Increased risk of cancer (skin, lung, bladder)

The International Agency for Research on Cancer (IARC) has classified arsenic as a group 1 carcinogenic. Group 1 indicates that there is sufficient data that links arsenic to cancer forming in one or more parts of the body. Arsenic has been most commonly linked to bladder, skin, and lung cancer. However, there has been some association with liver and kidney cancer.^5,6

Neurological and developmental effects

Effects on neurological and developmental factors include:⁴

• Anorexia
• Muscle weakness, pain, and paresthesia
• Blackfoot disease (Disease caused by long-term exposure to inorganic arsenic)
• Reynaud’s phenomenon
• Peripheral neuropathy

Cardiovascular diseases

In short-term arsenic poisoning, symptoms affecting the heart include:

• Cardiomyopathy
• Hypotension (low blood pressure)
• Shock
• Vasodilation

Diagnosis and detection

When exposed to arsenic, you should immediately seek medical advice. If you come in with suspected or known short-term arsenic poisoning, based on the situation or symptoms, your doctor may start treatment before it is confirmed to be arsenic poisoning by laboratory testing.

The best indicator of elevated arsenic levels is a urine sample if one can be collected within 24 hours of exposure. Confirmation of arsenic exposure is measured at 50 mg/L or over 100mg. In short-term exposure, arsenic levels in urine within the first 24 hours of exposure can exceed several thousand mg. Urine tests are done over time during treatment until the arsenic levels are below 50mg/L.

If the arsenic exposure is low threat, your doctor may recommend you stop eating high-arsenic associated foods, such as seafood or rice for 5 days before the initial urine test.

Other tests for arsenic levels include:

• Abdominal radiograph
• Various Blood tests 
  • Complete blood count
  • Comprehensive Metabolic Panel (CMP)
  • Haptoglobin
  • Peripheral smear
• Electrocardiogram (ECG)

Treatment and management

Arsenic poisoning requires immediate treatment that may require hospitalisation and life support monitoring. One of the most common therapies for short-term toxicity is chelation therapy. This involves being administered a medicine that sticks metal ions together so that they can be processed by the kidneys and removed from the body via urine.

It is most effective if started within minutes to hours after the short-term exposure, and its efficacy reduces over time. If necessary, a doctor will start the chelation therapy before laboratory confirmation. Common chelating agents used are:²

• British anti-lewisite (BAL)
• 2-3-dimercapto-1-propanesulfonate (DMPS)
• 2,3-dimer-captosuccinic acid (DMSA)

For long-term exposure, it is important to identify the source of the repeated exposure to eliminate further toxicity. Supportive therapy is the primary treatment for patients with long-term exposure. This includes treating the symptoms as they appear.

Prevention and regulation

Due to its chemical classification and threat to health, arsenic has standards and regulations established by the UK government. In food, the Commission Regulation (EU) 2015/1006 was introduced to establish the maximum levels of inorganic arsenic allowed.⁷ The Commission Regulation (EU) has reported that the biggest contributors to inorganic arsenic in diets were rice and rice-based products and contaminated drinking water.⁸ In rice and rice products targeted for infants and young children, the limit of arsenic is 0.1 mg/kg.⁹ In drinking water, the limit of arsenic allowed is 10 μg/L. 

Summary

Arsenic, or more specifically arsenic trioxide, is a highly toxic chemical that is commonly associated with famous murder mystery novels by Agatha Christie. Initially, it was a by-product of the metal industry and used as a poison for rats and mice. However, arsenic is a toxic substance that can cause considerable damage and death to those who are exposed to it. Thankfully, in the 1830s, regulations were put in place to regulate arsenic and control its accessibility. Arsenic is naturally found in nature from volcanic eruption and weathering of rocks. The most common cause of exposure is food and water contamination. Symptoms of arsenic poisoning include disruption to the gastrointestinal tract and damage to the nervous system. In long-term cases, there is a chance of cancer, cardiovascular problems, skin growth, and neurological damage. It is important to start immediate treatment after arsenic exposure. The antidote to arsenic poisoning is chelation therapy, where the treatment is most effective the earlier it is started. Due to the dangers of arsenic, governments around the world have implemented regulations to limit the amount of arsenic allowed in food and water levels as well as how much workers are allowed to be exposed to in a period.