Predictors of erythrocyte cadmium levels in 454 adults in Florence, Italy

Highlights

• We studied the predictors of erythrocyte Cd levels among 454 Italian adults.

• Smoking and the number of pack-years were the strongest predictor of Cd levels.

• Lifestyle (e.g. diet and physical activity) also played a significant role.

• Cd levels were higher among women and correlated with exposure to sex hormones.

Abstract

Background

Cadmium bioaccumulates in the body and causes several adverse health effects. Understanding the primary sources of exposure is critical in order to implement effective prevention measures.

Methods

We included 454 adults enrolled in the Florence cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC) during 1992–98. At enrolment, information was collected on demographics, lifestyle and dietary habits using validated questionnaires; anthropometric measures were taken; and a blood sample was collected from each study participant. Information on the residential and occupational history prior to enrolment was reconstructed by phone interviews. Cadmium levels were measured in erythrocytes using inductively coupled plasma-mass spectrometry. We used multiple linear regression models to investigate the main determinants of cadmium levels.

Results

Median erythrocyte cadmium levels were 0.66 μg/L (inter-quartile range 0.43–1.07 μg/L). Cadmium levels were lowest in never smokers (0.50 μg/L) and highest in current smokers (1.38 μg/L). Smoking status and the number of pack-years were the strongest predictors of cadmium levels in multivariable analysis, together with erythrocyte levels of lead, and biking to work, while an inverse association emerged with consumption of red meat and dairy products and physical activity levels. Cadmium levels were higher among women than men (0.66 vs. 0.58 μg/L), and, among the former, positively associated with late menopause, nulliparity, and use of hormones for menopause. The predictors included in the multivariable model explained >40% of the variability in erythrocyte cadmium levels.

Conclusions

Smoking was the most important determinant of erythrocyte cadmium levels, which were also affected by dietary habits, physical activity levels, biking, and (among women) hormone-related variables. Our results are important to inform public health actions aimed at reducing the impact of potentially modifiable sources of exposure to cadmium.

Introduction

Cadmium (Cd) is associated with a broad spectrum of adverse health effects on humans. Cadmium accumulation in the kidney and bone is known to cause tubular damage, renal dysfunction, osteomalacia, and osteoporosis (Jin et al., 2004; Järup and Akesson, 2009). In addition, cadmium and its compounds are classified as human group 1 carcinogens by the International Agency for Research on Cancer (IARC) as they are implicated in the pathogenesis of cancer of the lung, prostate and kidney (International Agency for Research on Cancer (IARC), 2012). Overall, cadmium represents a very serious threat to human health, and the implementation of measures aiming at reducing exposure to it should be regarded as an important public health priority.

Cadmium occurs naturally in the earth's crust and its environmental availability may increase temporarily due to volcanic activity; however, the most important sources of exposure to cadmium are usually anthropogenic. In fact, cadmium is widely used in industrial processes: it is a component of rechargeable nickel-cadmium batteries, televisions screens and pigments, and it is also used in electroplating in the aircraft industry, in galvanizing steel, and as a thermal neutron absorber in nuclear plants (Godt et al., 2006; Bernhoft, 2013). Humans are exposed to cadmium mostly via inhalation or ingestion. Cigarette smoking is considered as the main source of inhaled cadmium among non-occupationally exposed individuals; inhalation of cadmium fumes may occur in occupational settings as well, for instance during welding or soldering. An additional important anthropogenic source of cadmium emission into the environment is the incineration of cadmium-containing products (Ono, 2013). Cadmium can enter the human body also through diet: the foods highest in cadmium are leafy vegetables, rice, crustaceans and shellfish, offal, and edible mushrooms, and its uptake can be enhanced in case of deficiency of micronutrients such as iron, manganese and zinc (Godt et al., 2006; Bernhoft, 2013; Hajeb et al., 2014; Kippler et al., 2009). After absorption, cadmium is transported in the blood bound to proteins (like albumin and metallothionein), and is deposited mostly in the kidney and liver.

The multiplicity of sources and routes of exposure entails that the biological levels of cadmium may differ substantially between populations, and that a thorough investigation of its main determinants is necessary in order to maximize the effectiveness of any preventive intervention. This task is made even more urgent by the observation that, unlike other pollutants (e.g. lead and mercury), cadmium exposure in the general population does not appear to have decreased in recent decades in Europe (Lundh et al., 2016; Wennberg et al., 2017). Here, we aimed at identifying the main determinants of individual cadmium levels in a series of 454 adults residing in Tuscany, central Italy.