Silicosis: An explainer and research roundup

Silicosis is a progressive, debilitating and sometimes fatal lung disease caused by breathing silica dust from cutting, drilling, chipping or grinding materials such as granite, sandstone, slate or artificial stone. The dust gets trapped in the lung tissue, causing inflammation, scarring and permanent damage.

Silicosis is a job-related lung disease and has no cure. The disease mostly affects workers in construction, stone countertop fabrication, mining, and even those who sandblast and stonewash denim jeans to create a ‘worn out’ look.

Silica is one of the most common minerals in nature. About 59% of the Earth’s crust is made of silica, found in quartz, granite, sandstone, slate and sand. Historically, people at the highest risk for the disease have worked in natural environments — mining, digging tunnels or doing quarry work. The disease was first documented by the Greek physician Hippocrates, who in 430 B.C. described breathing disorders in metal diggers.

But in recent decades there’s been renewed attention to the disease due to its more rapid progression and severity among younger workers. Research has shown that the culprit is artificial stone mostly used for countertops for kitchens and bathrooms, which has a very high silica content.

The new generation of coal miners is also at an increased risk of silicosis, in addition to black lung, because layers of coal have become thinner, forcing them to dig deeper into rock, as explained in a joint investigation by the Pittsburgh Post-Gazette and the Medill Investigative Lab at Northwestern University published on Dec. 4. CBS Sunday Morning also had a report on the same issue among West Virginia coal miners, aired as part of its Dec. 10 episode.

Silicosis in modern industries

Artificial, or engineered, stone used for countertops, also known as “quartz,” is formed from finely crushed rocks mixed with resin. Quartz is a natural mineral, but man-made products like many quartz countertops consist of not just quartz, but also resin, colors and other materials that are used to style and strengthen them.

The silica content of artificial stone is about 90%, compared with the 3% silica content of natural marble and 30% silica content in granite stones, according to the authors of a 2019 systematic review published in the International Journal of Environmental Research and Public Health.

The first reported case of silicosis associated with working with artificial stone was from Italy in 2010, according to a 2020 study published in Allergy. Since then, more studies have documented the growing number of cases among artificial stone workers, many of whom are from marginalized populations, such as immigrants.

A July 2023 study published in JAMA Internal Medicine found that in California, the disease mainly occurred among young Latino immigrant men. The disease was severe in most men by the time they sought care.

An August 2022 study, published in Occupational & Environmental Medicine, analyzing the Global Silicosis Registry, with workers in Israel, Spain, Australia and the U.S., found “a substantial emerging population of workers worldwide with severe and irreversible silica-associated diseases,” due to exposure from silica dust from engineered stone.

Other modern occupations such as denim sandblasting, work on dental prostheses, manufacturing of electrical cables and working on jewelry and semi-precious stones also put workers at risk of silicosis.

In the wake of modern-day silicosis cases, researchers have called for larger studies to better understand the disease and the discovery of effective treatments.

In the U.S. about 2.3 million workers are exposed to silica dust on the job, according to the American Lung Association. Other estimates show approximately 10 million workers in India, 3.2 million in the European Union and 2 million in Brazil work with material containing silica.

However, “the reporting system for occupational injuries and illnesses in the United States fails to capture many cases, leading to a poor understanding of silicosis incidence and prevalence,” writes Ryan F. Hoy, who has published extensively on the topic, in a June 2022 article in Respirology.

A 2015 study in the Morbidity & Mortality Weekly Report found the annual number of silicosis deaths declined from 185 people in 1999 to 111 in 2013, but the decline appeared to have leveled off between 2010 and 2013, the authors write. Another 2015 study in MMWR, examining silicosis deaths between 2001 and 2010, found the death rate from silicosis was significantly higher among Black people compared with whites and other races. Men also have a significantly higher death rate from silicosis than women.

The 2019 Global Burden of Disease Study estimates that more than 12,900 people worldwide die from silicosis each year.

Silicosis has no cure, but it’s preventable when workers have access to proper respiratory protection and are educated on safe practices set by regulatory bodies such as the U.S. National Institute for Occupational Safety and Health. The European Network on Silica also has guidelines on handling and using materials containing silica. A March 2023 study published in Environmental Science and Pollution Research International finds that “education, training, and marketing strategies improve respirator use, while training and education motivate workers to use dust control measures.”

Silicosis symptoms and treatment

Symptoms of silicosis include cough, fatigue, shortness of breath and chest pain. There’s no specific test for silicosis. The first signs may show in an abnormal chest X-ray and a slowly developing cough, according to the American Lung Association.

Silicosis symptoms don’t appear right away in most cases, usually taking several years to develop working with silica dust. However, studies indicate that symptoms of silicosis due to exposure to artificial stone appear quicker than exposure to natural silica sources, potentially due to the higher concentration of silica in artificial stone.

There are three types of silicosis: acute (most commonly caused by working with artificial stone), accelerated and chronic, depending on the level of exposure to silica dust, according to the Centers for Disease Control and Prevention, which explains the severity of each type on its website.

Complications from silicosis can include tuberculosis, lung cancer, chronic bronchitis, kidney disease and autoimmune disorders. In some cases, silicosis can cause severe scarring of the lung tissue, leading to a condition called progressive massive fibrosis, or PMF. Some patients may require a lung transplant.

Lung damage from silicosis is irreversible, so treatment of silicosis is aimed at slowing down the disease and relieving its symptoms.

In 1995, the World Health Organization called for the elimination of silicosis by 2030, but research studies and news stories show it remains a threat to many workers.

Below, we have gathered several studies on the topic to help journalists bolster their reporting with academic research.

Research roundup

Artificial Stone Associated Silicosis: A Systematic Review
Veruscka Leso, et al. International Journal of Environmental Research and Public Health, February 2019.

This systematic review aims to verify the association between exposure to silica dust in artificial stone and the development of silicosis.

Researchers narrowed down their selection from 75 papers to seven studies that met their inclusion criteria. The seven studies were from Australia, Israel and Spain. Most of the studies are observational and impede a definite association between exposure to silica while working with artificial stone and developing silicosis, the authors note.

However, “the unusually high incidence of the disease that was reported over short periods of investigations, and the comparable occupational histories of affected workers, all being involved in the manufacture and manipulation of engineered stones, may indicate a cause-effect relationship of this type.”

The review of studies reveals a lack of basic preventive measures such as lack of access to disposable masks; lack of information and training on the dangers of silica dust; and lack of periodic medical examinations, including a chest X-ray, among workers. There was limited environmental monitoring of dust levels at the workplace. Also, there was no dust suppression system, such as the use of water when polishing the stones, or effective ventilation. Machinery and tools weren’t properly set up and didn’t undergo routine checks, the authors write.

The authors recommend environmental monitoring for assessing silica levels in the workplace and verifying the effectiveness of personal protections. They also recommend the health surveillance of workers exposed to silica dust.

“Stakeholders, manufacturers, occupational risk prevention services, insurance companies for occupational accidents and diseases, business owners, occupational health physicians, general practitioners, and also employees should be engaged, not only in designing/planning processes and operational working environments, but also in assessing the global applicability of proactive preventive and protective measures to identify and control crystalline silica exposure, especially in new and unexpected exposure scenarios, the full extent of which cannot yet be accurately predicted,” they write.

Silica-Related Diseases in the Modern World
Ryan F. Hoy and Daniel C. Chambers. Allergy, November 2020.

The study is a review of the mineralogy of silica, epidemiology, clinical and radiological features of the various forms of silicosis and other diseases associated with exposure to silica.

The primary factor associated with the development of silicosis is the intensity and duration of cumulative exposure to silica dust. Most countries regulate silica dust occupational exposure limits, generally in the range of 0.05 mg/m³ to 0.1 mg/m³, although the risk of dust exposure to workers still remains high at those levels.

The study provides a list of activities that could expose workers to silica dust. They include abrasive blasting of sand and sandstone; cement and brick manufacturing; mixing, glazing or sculpting of china, ceramic and pottery; construction involving bricklaying, concrete cutting, paving and demolition; sandblasting denim jeans; working with and polishing dental materials; mining and related milling; handling raw material during paint manufacturing; road and highway construction and repair; soap and cosmetic production; blasting and drilling tunnels; and waste incineration.

“Despite the large number of workers in the construction sector, there have been few studies of [silica dust] exposure in this industry,” the authors note.

Other than silicosis, conditions associated with silica exposure include sarcoidosis, an inflammatory disease that commonly affects the lungs and lymph nodes, autoimmune disease, lung cancer and pulmonary infections.

“Recent outbreaks of silica-associated disease highlight the need for constant vigilance to identify and control new and well-established sources of silica exposure. While there are currently no effective treatments for silicosis, it is a completely preventable lung disease,” the authors write.

A Systematic Review of the Effectiveness of Dust Control Measures Adopted to Reduce Workplace Exposure
Frederick Anlimah, Vinod Gopaldasani, Catherine MacPhail and Brian Davies. Environmental Science and Pollution Research International, March 2023.

This study provides an overview of various interventions and their effectiveness in preventing exposure to silica dust based on a review of 133 studies from 16 countries, including the U.S., Canada, China, India, Taiwan and Australia, and published between 2010 and 2020.

These dust control measures range from simple work practices such as the use of respirators to more sophisticated technologies, such as water and air curtains and foam technology, the authors note.

The review finds increasing research interest in dust reduction, mainly in China. But overall, regulatory influence remains inadequate in preventing miners’ exposure to silica dust.

“Results from the review suggest that adopted interventions increase knowledge, awareness, and attitudes about respirator usage and generate positive perceptions about respirator usage while reducing misconceptions,” the authors write. “Interventions can increase the use, proper use, and frequency of use of respirators and the adoption readiness for dust controls but may not provide sustained motivation in workers for the continual use of dust controls or [personal protective equipment.]”

Notes from the Field: Surveillance of Silicosis Using Electronic Case Reporting — California, December 2022–July 2023
Jennifer Flattery, et al. Morbidity and Mortality Weekly Report, November 2023.

This study examines the use of electronic case reporting to identify silicosis cases in California. Electronic case reporting, or eCR, is the automated, real-time exchange of case report information between electronic health records at health facilities at state and local public health agencies in the U.S. It is a joint effort between the Association of Public Health Laboratories, the Council of State and Territorial Epidemiologists, and the CDC. Currently, 208 health conditions can be reported using eCR. All 50 states and other U.S.-affiliated jurisdictions are connected to eCR. Once a public health agency receives a case report, it reaches out to the patient for contact tracing or other actions.

From October 2022 to July 2023, the California Department of Public Health received initial silicosis case reports for 41 individuals. A review of medical records confirmed 19 cases and 16 probable cases. Six of the 41 cases were considered unlikely to be silicosis after a review of medical records.

Notably, engineered stone countertop fabrication was a significant source of exposure, especially among Hispanic and Latino workers.

At least seven of the 19 confirmed cases were associated with the fabrication of engineered stone — quartz — countertops. The 19 patients’ ages ranged from 33 to 51 and all were Hispanic or Latino. One patient died and two had both lungs replaced. One was evaluated for a lung transplant.

The median age of the 35 patients with probable or confirmed silicosis was 65, ranging from 33 to 89 years, and 91% were men.

“It is important that health care providers routinely ask patients about their work as an important determinant of health,” the authors write. “Being aware of the risks associated with work exposures, as well as the regulations, medical monitoring, and prevention strategies that address those risks can help guide patient care.”