Heavy metals as risk factors for human diseases - a Bayesian network approach.

Modern industrial agricultural processes expose human beings to multifactorial environmental pollution including heightened levels of heavy metals. The effects of acute heavy metal exposures at toxic levels are usually known; they are tested for and treated promptly. The effects of low/moderate-level chronic heavy metal exposures are less known as they may be subclinical, and pathogenic effects may only manifest clinically over time under the disguise of a diagnosable disease or miscellaneous symptoms attributed to aging. Consequently, the health impact of low-moderate heavy metal exposure is unlikely to be identified. Furthermore, established heavy metal safety levels often fail to recognize the potential toxic effects on humans. We report in this review what is known about the sub-chronic and chronic effects of exposure to heavy metals, particularly lead, mercury, cadmium, arsenic, and nickel, and we highlight their possible effects in the brain, cardiovascular and endocrine-metabolic systems, and on reproduction.

The World Trade Center health surveillance program: results of the first 10 years and implications for prevention.

BACKGROUND: The terrorist attacks on the World Trade Center (WTC) of September 11, 2001 resulted in the deaths of 2,823 persons. They also generated a long-lasting burden of multiple physical and mental health illnesses among the cohort of 50,000 rescue workers who responded to the attacks and in the 400,000 residents and workers in nearby areas of New York City. A comprehensive health surveillance program was developed from the first months after the accidents and was further developed in the subsequent ears. Individual exposure and health data were stored in ad hoc databases and produced epidemiological outcomes on the various exposure-related illnesses. METHODS: About 10 years of longitudinal assessment of this large cohort of WTC rescue and recovery workers, yielded data from participants in the WTC Screening, Monitoring, and Treatment Program. Police officers, firefighters, construction workers, and municipal workers were included in the cohort. Cumulative and annual incidence were estimated for various physical disorders including asthma, sinusitis, and gastroesophageal reflux disease, mental health disorders including depression, post-traumatic stress disorder [PTSD], and panic disorder. Respiratory functionality was also assessed. Exposure was characterized with qualitative parameter including working on the pile and being engulfed in the dust cloud, and quantitative parameters including the time of arrival on site and the exposure duration. RESULTS: Upper and lower respiratory conditions such as rhinosinusitis and asthma have been found in a significant number of people in WTC-exposed populations. A lack of appropriate respiratory protection may have contributed to these effects. Other commonly observed physical health conditions include gastro-esophageal reflux disease, obstructive sleep apnea and musculo-skeletal injuries. Many WTC-exposed individuals also suffer from mental health conditions, primarily post-traumatic stress disorder, depression, panic disorder, and substantial stress reaction. Recent studies suggest that WTC exposure may increase the risk of cancer and of mortality from cardiac disease. CONCLUSION: Ten years of systematic health surveillance after the 9/11 WTC attacks, show long lasting burden of physical and mental health problems. Continued monitoring and treatment of this population is needed for early diagnoses of initial clinical conditions that can be treated more effectively. The experience of September 11 offers also indications on how to approach the acute and delayed health effects of civilian catastrophes. Critical lessons are derived about the importance of having trained responders--medical and non-medical--in place in advance of disasters, and about the need to proceed with adequate exposure assessment in a timely manner.

Neurological impacts from inhalation of pollutants and the nose-brain connection.

The effects of inhaled particles have focused heavily on the respiratory and cardiovascular systems. Most studies have focused on inhaled metals, whereas less information is available for other particle types regarding the effects on the brain and other extra-pulmonary organs. We review here the key available literature on nanoparticle uptake and transport through the olfactory pathway, the experimental data from animal and in vitro studies, and human epidemiological observations. Nanoparticles (<0.1 µm in one dimension) may easily reach the brain from the respiratory tract via sensory neurons and transport from the distal alveoli into the blood or lymph as free particles or inside phagocytic cells. These mechanisms and subsequent biologic responses may be influenced by the chemical composition of inhaled particles. Animal studies with ambient particulate matter and certain other particles show alterations in neuro-inflammatory markers of oxidative stress and central neurodegeneration. Human observations indicate motor, cognitive, and behavioral changes especially after particulate metal exposure in children. Exposure to co-pollutants and/or underlying disease states could also impact both the biokinetics and effects of airborne particles in the brain. Data are needed from the areas of inhalation, neurology, and metal toxicology in experimental and human studies after inhalation exposure. An increased understanding of the neurotoxicity associated with air pollution exposure is critical to protect susceptible individuals in the workplace and the general population.