Manufacturing

Burden

Cancer is a leading cause of death in the U.S. and the world [American Cancer Society 2016]. Based on well-documented associations between occupational exposures and cancer, researchers have estimated that between 2-8% of all cancers worldwide are caused by exposures to carcinogens in the workplace [Driscoll et al. 2005; Rushton et al. 2012; Purdue et al. 2015, Steenland et al. 2003]. Using cancer incidence numbers in the U.S., this means that in 2013, there were between 31,180 and 124,720 new cancer cases that were caused by past exposure in the workplace [Rushton et al. 2010]. NIOSH burden data show that the following cancers are an important source of morbidity among workers in the manufacturing sector: lung and bronchus cancer (attributable fraction [AF] = 8-11 %); mesothelioma (AF = 1-19 %); leukemia (AF = ~4%); laryngeal cancer (AF = 2-7 %); and sinonasal and nasopharynx cancer (AF = 41-54%) [Groenewold et al. 2017].

Need

High priority agents for study within the manufacturing sector include nanomaterials (specifically, carbon nanoparticles) and welding fumes; emerging agents of concern related to occupational cancer among workers in this sector include plasticizers and flame retardants. Each of these categories of agents includes multiple specific agents of concern – the type of research needed for the different specific agents will vary depending on the amount of work that has been performed to this point. For example, among the many types of nanomaterials, etiologic epidemiologic research would be most appropriate currently only for carbon-based nanomaterials, while other types of etiologic research (toxicologic, basic exposure) and intervention research is needed for carbon-based nanomaterials but also for a number of other types of nanomaterials. Information is also needed on the occupational exposure levels to potentially carcinogenic chemicals that are in new or increased use, such as flame retardant chemicals and bisphenol A (BPA) and other plasticizers being proposed as substitutions for BPA. BPA was recently listed as “high priority” for review by the International Agency for Research on Cancer (IARC 2014), based on anticipated information from toxicology studies. Concomitant occupational exposure assessment would be very timely for such an assessment.

The need for etiologic and intervention research in the manufacturing sector is justified by: (1) the frequency with which studies conducted in this sector have contributed information about known human carcinogens (e.g., asbestos, benzene, beryllium, ortho-toluidine, vinyl chloride); (2) the fact that the population is relatively stable, can be documented, and exposures may be concentrated and measurable among this workforce; and (3) importantly, cancers that occur as a result of exposures in the workplace are preventable, if exposures to known or suspected carcinogens can be reduced.

Burden

Adverse reproductive outcomes can affect both men and women and can include infertility, menstrual cycle changes, pregnancy loss, pregnancy complications, and congenital malformations in offspring. Specifically concerning one type of adverse reproductive outcome, congenital malformations affect one in every 33 babies (about 3% of all babies) born in the U.S. each year. While most adverse reproductive outcomes are related to a number of different etiologic factors, occupational exposures likely play an important and perhaps under-recognized role. For example, it has been estimated that 3% of major malformations among live births are due to toxicant exposures, 28% can be attributed to genetic causes, and approximately 23% are attributable to multifactorial causes, which are complex interactions between genes and environmental factors [CDC 2008, 2017; Macdorman and Gregory 2015; Mathews et al. 2015; Thoma et al. 2013].

Need

Toxicants with reported reproductive and developmental effects are in regular commercial use and thus present potential exposure to workers. High priority agents to which workers in the manufacturing sector may be exposed include heavy metals, organic solvents, and the large class of agents characterized as endocrine disrupters. Bisphenol A (BPA) is an important endocrine disrupter for which basic/etiologic research (as well as intervention research) is needed. In more general terms, the need for research in the manufacturing sector is bolstered by the fact that progress has been limited in identifying new reproductive hazards, quantifying their potencies, and separating the contribution of these hazards from other etiologic factors. The pace of laboratory studies to identify hazards and to underpin the biologic plausibility of reproductive effects in humans has not matched the pace at which new chemicals are introduced into commerce.

Burden

Neurologic disorders, which may be associated with occupational exposures include neurodegenerative diseases (such as the motor neuron diseases (MND), Parkinson’s disease (PD), dementias, and multiple sclerosis) and other conditions such as peripheral neuropathies and chronic toxic encephalopathies. Clinical syndromes associated with neurotoxicity comprise one of the 10 leading occupational disorders in the U.S., and neurotoxic effects are the basis for exposure limit criteria for about 40% of the agents considered hazardous by NIOSH [Pearce and Kromhout 2014]. Welding is a common activity occurring in many industrial sectors but is particularly common in the manufacturing sector. There is a concern about potential neurological effects associated with welding, and specifically concerning exposure to manganese in welding fumes [Al-Lozi et al. 2017].

Need

Current knowledge indicates that occupational and environmental exposures cause an uncertain proportion of most types of neurodegenerative disease. In addition, for some common neurodegenerative diseases (e.g., MND and PD) the incidence is higher in men than in women, which suggests occupational causes [Pearce and Kromhout 2014]. However, so far no occupational agent has been identified that is responsible for a significant number of cases, reflecting the “emerging” nature of the study of occupational neurologic diseases compared to some other health outcomes. Focused etiologic research could help to ascertain whether workplace exposures are contributing to this burden.

While it is recognized that prolonged exposure to high manganese concentrations in air may lead to a Parkinsonian syndrome known as “manganism,” research is mixed concerning neurological and neurobehavioral deficits occurring when workers are exposed to low levels of manganese in welding fumes over time. Workers performing welding operations in the manufacturing sector may experience other exposures as well, such as to lead, iron, carbon monoxide, heat and stress, which can also contribute to neurological impairments. Research from NIOSH and other researchers can play an important role in furthering our understanding of the etiology and towards the development and evaluation of control interventions for the prevention of those occupational health effects.